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Nanocomposites with a natural rubber (NR) matrix containing organomodified montmorillonite (MMT) as a precursor of nanoparticles were prepared using two different polyoxazolines as surface modifiers of the MMT. The materials were characterized by X-ray diffraction, transmission electronic microscopy and ultimate mechanical properties, and parameters obtained by DMTA method (storage and loss moduli and loss tangent) were determined. It was found that the effect of nanofillers presence has a significant effect on tensile strength as well as elongation at break, which are higher for materials with higher viscosity due to the presence of carbon blacks compared to the composites without carbon blacks. From the two modifiers, poly(2-ethyl-2-oxazoline) was identified as a prospective modifier for surface modification of MMT used as the possible additive for tyre treads exhibiting optimal balance between fuel consumption and safety of driving concerning breaking action and lateral breakaway. [ABSTRACT FROM AUTHOR]

• Degradation processes in polyolefin plaques initiated by applying non-ionizing or ionizing radiation have been compared. • Plaques were prepared by melt-mixing of polyolefin with particular natural stabilizer and with or without spin trap TTBNB. • Generated radicals and structure changes caused by degradation processes were characterized by ESR and IR, respectively. • Presence of spin trap TTBNB made possible catching short-living radicals in HDPE, that could not be detected previously. • Polymer dynamics related to T g affects reactivity of generated radicals and concentration of created oxidation products. We investigated degradation processes in polymer plaques made of polyolefin (HDPE or UHMWPE or COC) prepared by melt-mixing with or without phenolic stabilizer (natural α-tocopherol or synthetic Irganox®1010) and spin trapping agent (TTBNB; 2,4,6-Tri‑tert-butylnitrosobenzene). The degradation was initiated either by low-energy, non-ionizing radiation (wavelengths corresponding to terrestrial range of solar UV radiation) or high-energy, ionizing radiation (electrons accelerated at 1.5 MeV). The motivation for the study was our recent finding that some phenolic stabilizers exhibited a surprising pro-oxidant activity in polyolefins subjected to non-ionizing radiation. Consequently, we asked if the phenolic stabilizers in polyolefins behave in the same way during long-term, low-energy, non-ionizing UV irradiation and after short-term, high-energy, ionizing e-beam irradiation. All samples were characterized thoroughly by means of electron spin resonance (ESR; the information about radiation-induced radicals), infrared microspectroscopy (IR; the detection of oxidation products and structural changes), instrumented microindentation (MHI; local mechanical properties) and light and electron microscopy (LM and SEM; surface morphology). The results proved that (i) the degradation processes in polyolefins subjected to non-ionizing or ionizing radiation were different, (ii) the phenolic stabilizers exhibited mostly their expected antioxidant activity, while pro-oxidant activity was detected only for specific conditions and/or systems subjected to non-ionizing radiation, and (iii) the selected spin trapping agent, TTBNB, was stable enough to survive standard sample preparation by melt-mixing and catch short-living unstable radicals. [ABSTRACT FROM AUTHOR]

Polymer plaques made of high density polyethylene (HDPE) and of two types of cycloolefin copolymer (COC) differing in glass transition temperature, were stabilized with 0.2 or 1.0 wt % of natural (α-tocopherol) or synthetic (Irganox®1010) phenolic stabilizer or hindered amine stabilizer (Tinuvin®770) and aged using accelerated weathering technique (WOM). The efficiency of the phenolic stabilizers was compared among themselves and with well-established Tinuvin®770. Concentration profiles of radicals generated inside polymer plaques during WOM exposure were determined by ESRI, profiles of oxidation products and crystallinity inside the HDPE plaques were determined by IR microspectroscopy, oxidation products in COC copolymers were identified using ATR, the changes of local mechanical properties of the polymer plaques were characterized using microindentation hardness testing, and their morphology was studied by light and/or scanning electron microscopy. All the techniques evidenced high stability of neat COC against photooxidation processes, whereas neat HDPE exhibited fast photooxidation of the surface layers. Tinuvin®770 was found to provide long term protection to both HDPE and COC against photodegradation. In contrast, the same polymers stabilized with the natural phenolic antioxidant α-tocopherol (the most active component of vitamin E) or synthetic phenolic antioxidant Irganox®1010 exhibited an increase in the surface oxidation in comparison with the neat polymers during WOM exposure, proving prooxidant activity of phenolic stabilizers during WOM exposure in all polymers studied. The prooxidant activity α-tocopherol was stronger in comparison with Irganox®1010. We conclude that neither of the two phenolic stabilizers was able to provide long term protection of the investigated polymers against photooxidation. • Accelerated weathering of HDPE and COC polymers stabilized with phenolic stabilizer. • Prooxidation activity of 1% of α‑tocopherol or Irganox® 1010 during photooxidation. • Limited prooxidation activity at lower concentration of stabilizers (0.2 wt %). • The stabilizers do not protect the polymers subjected to photooxidation. [ABSTRACT FROM AUTHOR]

Abstract UV irradiation and thermal degradation were studied in marine conditions for styrene-butadiene rubber (SBR) and high density poly (ethylene) (HDPE) containing a Tinuvin® 770 hindered amine stabilizer. Electron spin resonance imaging (ESRI) was used to monitor degradation process in various depths and compare the polymers in terms of robustness to UV irradiation. In addition, both oxidative degradation and mechanical properties were studied by microscale methods, such as infrared microspectroscopy (IR) and microindentation hardness testing (MHI), enabling us to compare the material changes locally, i.e. both at the exposed surfaces and inside the samples. In SBR/Tin770 system, Tinuvin®770 stabilizer failed to protect the polymer matrix against photooxidation as clearly seen from IR/ATR spectra. The Weather-Ometer (WOM) aging resulted in strong oxidative degradation of both non-stabilized and stabilized SBR and caused remarkable changes in three regions of IR/ATR spectra. The strong photooxidative degradation was also manifested through the micromechanical properties of SBR/Tin770 systems. The change of the local properties was the same (within the standard deviations) for both stabilized and non-stabilized samples, which confirmed negligible stabilization efficiency of Tinuvin® 770 in the SBR system. In contrast to the SBR systems, similar experiments showed very dramatic stabilization effects in the HDPE/Tin770 system. ESR and 2D spectral-spatial ESRI directly proved the different degradation behavior of the two types of the composites: whereas in the SBR composites fast degradation was observed, high density poly (ethylene) showed much slower degradation. We attributed such striking difference to the modification of Tinuvin® 770 hindered amine stabilizer after vulcanization during preparation of SBR rubber, which apparently eliminated most of its protective activity. Highlights • Degradation of styrene-butadiene rubber (SBR) and high density polyethylene (HDPE) with Tinuvin® 770 stabilizer were studied. • In SBR/Tin770 system, Tinuvin®770 stabilizer failed to protect the polymer matrix against photooxidation. • In contrast to the SBR systems, similar experiments showed very dramatic stabilization effects in the HDPE/Tin770 system. • ESR and 2D spectral-spatial ESRI directly proved the different degradation behavior of the two types of the composites. • The difference is attributed to change of Tinuvin® 770 during SBR preparation, which limited most of its protective activity. [ABSTRACT FROM AUTHOR]

Photooxidation processes inside high-density polyethylene (HDPE) and cyclic olefin copolymer (COC) poly(ethylene- co -norbornene), both stabilized with biological antioxidant α-tocopherol (α-T-OH), has been investigated. Plaques made of the polymers stabilized with α-T-OH were subjected to long-term accelerated weathering in a Weather-Ometer (WOM). Concentration profiles of radicals generated in the plaques in dependence on WOM exposure time were determined by electron spin resonance imaging (ESRI). Concentration profiles of oxidation products and stabilizer, together with local crystallinity profiles inside the polymer plaques were determined by infrared (IR) microspectroscopy. The ESRI and IR profiles, supplemented by light microscopy (LM) and microindentation hardness measurements (MH), revealed the heterogeneity of the oxidation process and, surprisingly, the pro-oxidative activity of α-T-OH. Increasing concentration of products of polymer oxidation was found in the surface layers of the plaques stabilized with α-T-OH since the beginning of WOM treatment unlike the same control experiments with polymer plaques stabilized with HAS Tinuvin ® 770, where no oxidation products were observed after the same treatment before HAS depletion. We have confirmed that α-T-OH exhibits antioxidant activity during thermooxidation but it acts as a pro-oxidant agent during photooxidation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Stability of Ti 3 C 2 O x F x MXene in air and argon. • Combined XPS and TEM study, including electron diffraction. • Ti4+ state and TiO 2 formation during aging in air has been proved. • Proper storage of MXenes results in high stability in air (>337 days). Different batches of Ti 3 C 2 O x F x MXene were prepared, and their stability in air and argon was studied. X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) in multiple modes (bright field imaging, energy-dispersive X-ray analysis, and selected-area electron diffraction) was employed to study the chemical and morphological changes in two-dimensional (2D) MXene exposed to air for several days and months. We observed the progressive development of the Ti4+ state accompanied by the development of TiO 2 formation, which lead to a slow disintegration of the 2D MXene nanosheets, although their overall morphology and crystalline structure can persist for several months. The presence of water is found to play an important role in the hydrolysis and degradation reactions during MXene aging. Our XPS and TEM studies show how the surface chemistry changes during aging in air and which surface termination groups are indicative of stable Ti 3 C 2 O x F x MXene and which storage conditions can stabilize MXene for more than 337 days. [ABSTRACT FROM AUTHOR]

High-quality titanate nanotubes (TiNT) were mixed with modified polypropylene (PP*) by a batch melt-mixing procedure. To improve compatibility between the nanofiller and the matrix, polypropylene (PP) was modified by electron beam irradiation. Effects of TiNT nanoparticles on crystallization, mechanical, thermal and rheological properties of the modified polypropylene were studied and compared with the analogous systems filled with commercial micro- (mTiO) and nano- (nTiO) titanium dioxide particles. Nucleation effects of the TiO-based fillers on PP* crystallization were investigated in detail. The microstructure of the PP*/TiNT nanocomposites shows well-dispersed TiNT sparse aggregates (clouds), penetrated by the polymer. A large-scale structure in the nanocomposite melts confirmed also rheology. In comparison to the matrix characteristics, the stiffness and microhardness of the TiNT nanocomposites increase by 27 and 33 %, respectively. The enhancement in mechanical properties demonstrates that the quality titanate nanotubes can be used as an efficient filler in non-polar polymers using the polymers modified by irradiation. In the case of the nanocomposites containing nTiO-anatase particles, the increase in these mechanical characteristics is lower. The investigated changes in the rate of crystallization indicate a marked nucleation effect of the nanotubes. The crystallization kinetics data, processed by the Avrami equation, suggest 3-dimensional crystal growth in the polypropylene matrix. The observed improvement in mechanical properties of the TiNT nanocomposites is induced not only by the nanofiller reinforcement but also by the changes of supermolecular structure of the polymer matrix due to nucleated crystallization. [ABSTRACT FROM AUTHOR]

Abstract: Morphology of polystyrene-block-poly(acrylic acid) vesicles was imaged by various modes of scanning electron microscopy (SEM), including recently developed wet scanning transmission electron microscopy (wet-STEM) by means of which we were able to follow the decrease in the thickness of a liquid solvent layer around the vesicles during controlled evaporation of water from the sample. Results show that wet-STEM allows for imaging of nanosized polymeric particles in the presence of the solvent. [Copyright &y& Elsevier]

Abstract: Stable Pd nanoparticles (PdNP) with a tunable size (3–15nm) were synthesized by controlled chemical reduction of PdCl2 with sodium citrate in water. The morphology of PdNP was characterized by transmission electron microscopy, while their stability in solution was verified by quasi-elastic light scattering and small-angle X-ray scattering. Intensive stirring of reacting mixture played a vital role in achieving reproducible particle sizes. Controlled changes of pH and initial concentrations were employed in fine-tuning particle size distributions. Finally, 10nm PdNP were conjugated with goat anti-mouse IgG antibody as proved by electrophoresis (SDS–PAGE) and used for ultrastructural immunolabeling, which confirmed suitability of PdNP for multiple immunolabeling in biomedicine. [Copyright &y& Elsevier]

• Accelerated weathering of HDPE and COC polymers stabilized with natural phenolic stabilizer (+)-catechin. • Results of IR microspectroscopy, ATR spectroscopy, ESRI, microindentation hardness testing (MHI), and light and/or scanning electron microscopy are in accordance with the conclusion that the natural phenolic stabilizer CAT exhibited pro-oxidant activity during accelerated photooxidation of both polymers and is not able protect the polymers against photooxidation. • At presence of TTBNB as the second additive adducts of polymer alkyl radicals generated in both polymers to TTBNB were detected. In this way TTBNB acted as processing stabilizer but no protective activity against photodegradation was connected with its presence. Polymer plaques made of high-density polyethylene (HDPE) or cycloolefin copolymer (COC) were stabilized with natural phenolic stabilizer (+)-catechin (CAT) and aged using accelerated weathering technique (WOM; accelerated photooxidation). The efficiency of the phenolic stabilizer was compared with a well-established hindered amine stabilizer (HAS) Tinuvin®770 (Tin770). In pursuit of the stabilization and identification of short-living radicals generated in the process of photooxidation of the polymers, a spin trapping agent 2,4,6-tri-tert-butylnitrosobenzene (TTBNB) was added to selected samples. Profiles of oxidation products and crystallinity inside the HDPE plaques were determined by IR microspectroscopy, oxidation products in COC copolymers were identified using ATR spectroscopy, concentration profiles of radicals generated inside polymer plaques during WOM exposure were determined by ESRI, the changes of local mechanical properties at the surface of polymer plaques were characterized using microindentation hardness testing (MHI), and the surface morphology changes were studied by light and/or scanning electron microscopy. All methods are in accordance with the conclusion that the natural phenolic stabilizer CAT exhibited pro-oxidant activity during accelerated photooxidation of both polymers, i.e. higher concentration of oxidation products, bigger changes of local mechanical properties and/or more microcracks on the exposed surfaces in comparison with non-stabilized systems and systems stabilized with Tin770. [ABSTRACT FROM AUTHOR]

Today, ultramicrotome cutting is a practical tool, which is frequently applied in the preparation of thin polymeric films. One of the advantages of such a technique is the decrease in surface roughness, which enables an effective recording of further morphological changes of polymeric surfaces during their processing. In view of this, we report on ultramicrotome-cut polymers (PET, PEEK) modified by a KrF excimer laser with simultaneous decoration by AgNPs. The samples were immersed into AgNP colloid, in which they were exposed to polarized laser light. As a result, both polymers changed their surface morphology while simultaneously being decorated with AgNPs. KrF laser irradiation of the samples resulted in the formation of ripple-like structures on the surface of PET and worm-like ones in the case of PEEK. Both polymers were homogeneously covered by AgNPs. The selected area of the samples was then irradiated by a violet semiconductor laser from the confocal laser scanning microscope with direct control of the irradiated area. Various techniques, such as AFM, FEGSEM, and CLSM were used to visualize the irradiated area. After irradiation, the reverse pyramid was formed for both types of polymers. PET samples exhibited thicker transparent reverse pyramids, whereas PEEK samples showed thinner brownish ones. We believe that his technique can be effectively used for direct polymer writing or the preparation of stimuli-responsive nanoporous membranes. [ABSTRACT FROM AUTHOR]

In this article, we present a unique combination of techniques focusing on the immobilization of noble metal nanoparticles into a honeycomb polystyrene pattern prepared with the improved phase-separation technique. The procedure consists of two main steps: the preparation of the honeycomb pattern (HCP) on a perfluoroethylenepropylene substrate (FEP), followed by an immobilization procedure realized by the honeycomb pattern's exposure to an excimer laser in a noble metal nanoparticle solution. The surface physico-chemical properties, mainly the surface morphology and chemistry, are characterized in detail in the study. The two-step procedure represents the unique architecture of the surface immobilization process, which reveals a wide range of potential applications, mainly in tissue engineering, but also as substrates for analytical use. [ABSTRACT FROM AUTHOR]

Today, it would be difficult for us to live a full life without polymers, especially in medicine, where its applicability is constantly expanding, giving satisfactory results without any harm effects on health. This study focused on the formation of hexagonal domains doped with AgNPs using a KrF excimer laser (λ=248 nm) on the polyetheretherketone (PEEK) surface that acts as an unfailing source of the antibacterial agent - silver. The hexagonal structure was formed with a grid placed in front of the incident laser beam. Surfaces with immobilized silver nanoparticles (AgNPs) were observed by AFM and SEM. Changes in surface chemistry were studied by XPS. To determine the concentration of released Ag+ ions, ICP-MS analysis was used. The antibacterial tests proved the antibacterial efficacy of Ag-doped PEEK composites against Escherichia coli and Staphylococcus aureus as the most common pathogens. Because AgNPs are also known for their strong toxicity, we also included cytotoxicity tests in this study. The findings presented here contribute to the advancement of materials design in the biomedical field, offering a novel starting point for combating bacterial infections through the innovative integration of AgNPs into inert synthetic polymers. • Anchoring of silver nanoparticles and creation of silver-riched domains. • Presence of nanostructures in form of globules and ripples with nanoparticles. • Majority of nanoparticles presented close to the surface. • Strong bactericidal effect against Escherichia coli and Staphylocuccus aureus. [ABSTRACT FROM AUTHOR]

The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels.The superporous thermosensitive PNIPA/clay hydrogels were prepared by the advanced two-step freezing polymerization. The formation and properties of the cryogels were controlled by freezing conditions, such as time of freezing during the two-step polymerization and the rate of cooling. The freezing of the reaction mixture in different well-defined stages of structure evolution during polymerization made it possible to fine tune the structure, morphology, and properties of cryogels. The development of structure during polymerization was followed by NMR and chemorheology, and moreover, the morphology, porosity, swelling behavior, and mechanical properties of the cryogels were determined. The results contribute to the basic understanding of the structure evolution under freezing conditions and to the knowledge of the mechanism of a cryogel formation. The smart thermoresponsive gels with a wide variety of properties were prepared, ranging from the weak ultrafast responding cryogels (deswelling in 30 s, reswelling in 8 min), prepared by the early freezing, up to the porous gel with extraordinary mechanical properties (σb = 320 kPa, εb = 900%) still displaying a relatively fast thermal volume transition. The advanced two-step freezing polymerization is shown to be a suitable general approach to controlling and tuning porosity, as well as swelling and mechanical properties of porous gels. [ABSTRACT FROM AUTHOR]

Polymer-based membranes represent an irreplaceable group of materials that can be applied in a wide range of key industrial areas, from packaging to high-end technologies. Increased selectivity to transport properties or the possibility of controlling membrane permeability by external stimuli represents a key issue in current material research. In this work, we present an unconventional approach with the introduction of silver nanoparticles (AgNPs) into membrane pores, by immobilising them onto the surface of polyethyleneterephthalate (PET) foil with subsequent physical modification by means of laser and plasma radiation prior to membrane preparation. Our results showed that the surface characteristics of AgNP-decorated PET (surface morphology, AgNP content, and depth profile) affected the distribution and concentration of AgNPs in subsequent ion-track membranes. We believe that the presented approach affecting the redistribution of AgNPs in the polymer volume may open up new possibilities for the preparation of metal nanoparticle-filled polymeric membranes. The presence of AgNPs on the pore walls can facilitate the grafting of stimuli-responsive molecules onto these active sites and may contribute to the development of intelligent membranes with controllable transport properties. [ABSTRACT FROM AUTHOR]

In the case of polymer medical devices, the surface design plays a crucial role in the contact with human tissue. The use of AgNPs as antibacterial agents is well known; however, there is still more to be investigated about their anchoring into the polymer surface. This study describes the changes in the surface morphology and behaviour in the biological environment of polyetheretherketone (PEEK) with immobilised AgNPs after different surface modifications. The initial composites were prepared by immobilising silver nanoparticles from a colloid solution in the upper surface layers of polyetheretherketone (PEEK). The prepared samples (Ag/PEEK) had a planar morphology and were further modified with a KrF laser, a GaN laser, and an Ar plasma. The samples were studied using the AFM method to visualise changes in surface morphology and obtain information on the height of the structures and other surface parameters. A comparative analysis of the nanoparticles and polymers was performed using FEG-SEM. The chemical composition of the surface of the samples and optical activity were studied using XPS and UV-Vis spectroscopy. Finally, drop plate antibacterial and cytotoxicity tests were performed to determine the role of Ag nanoparticles after modification and suitability of the surface, which are important for the use of the resulting composite in biomedical applications. [ABSTRACT FROM AUTHOR]

• Amphiphilic copolymers with dendritic PE core and polyHEMA grafts prepared. • dPE-graft-PHEMA form 60–180 nm nanoparticles stable in water. • Self-assembly behavior is influenced by molar mass of copolymers. • Nanoparticles encapsulate hydrophobic Nile Red dye with up to 25% efficiency. By grafting from approach amphiphilic grafted copolymers with a hydrophobic core based on dendritic polyethylene and hydrophilic grafts of polyhydroxyethylmethacrylate (PHEMA) and polyhydroxypropylmethacrylate (PHPMA) were synthesized by tandem chain walking copolymerization and ATRP. Copolymers with molar mass 160–1400 kg/mol and ∼50–90% of hydrophilic grafts were obtained. Core-shell nanoparticles with very narrow size distribution were prepared from the copolymers by solvent displacement method. Particles diameter was efficiently regulated by molar mass of the copolymers in the range of 60–180 nm. We demonstrated that these nanoparticles can act as nanocontainers for hydrophobic Nile red dye, achieving up to 25% encapsulation efficiency. Dendritic polyethylene (dPE) nanoparticles with biocompatible polar PHEMA and PHPMA shell can find application in nanocatalysis and cargo delivery. [ABSTRACT FROM AUTHOR]

An advanced and inexpensive one-pot method to prepare polystyrene (PS)-barium titanate (BT) films by solution mixing is reported. The process was developed to obtain free-standing films with an increased dielectric constant (ε′). Since PS is soluble in apolar solvents, BT nanoparticles (BT-NPs) were surface-modified with palmitic acid (PAc) and embedded within the polymer matrix without affecting homogeneity and smoothness of the composite. The films were prepared by floating method consisting in dropping BT-NPs dispersed in PS/toluene solution on the water surface. After the evaporation of toluene, smooth, free-standing and thermally stable films were obtained with a markedly higher ε′ compared to the neat PS. PAc modification improved the dispersion of BT-NPs in the apolar phase and prevented their diffusion into the aqueous phase during the toluene evaporation. The proposed film-forming technique makes it possible to modulate the thickness and shape of the films by selecting the quantity and concentration of the organic phase and using various templates, thus opening up a broad range of applications. [ABSTRACT FROM AUTHOR]

The monolayer form of CVD graphene is imposing crucial challenges in characterization of the targeted covalent functionalization due to the low amount of grafting moieties on the surface, which in turn hampers drawing conclusions about reactivity-properties relationships. Due to the growing interest in chemically modified graphene new, reliable and non-destructive methods for its characterization are critically required. Herein we demonstrate the use of surface-enhanced infrared absorption spectroscopy for detection of characteristic vibration modes of species being grafted to the material either via radical (Meerwein arylation) or nucleophilic substitution pathway on copper foil. The phenomenon is allowed by the appropriate metal surface morphology and no signal could have been obtained neither on Si/SiO 2 substrate, nor on bare copper. The surface of copper foil exhibit partial corrosion during the reaction which leads to the creation of active substrate for SEIRA. The measurements were performed using reflection-absorption and attenuated total reflection modes with almost identical results, thus making this analytical approach feasible, practical, non-destructive and easy to use for routine characterization of graphene functionalization. [ABSTRACT FROM AUTHOR]

The interest for ZrP this material is based on its physicochemical properties which makes this material a perspective candidate for applications in nuclear medicine. In this study ZrP was prepared and completely characterized using various analytical methods. Finally, the study of radiometals sorption mechanism on a surface of ZrP and the surface characterization of ZrP were done. In conclusion, ZrP appears as promising for next studies with various purposes like drug delivery system or ion-exchanger for separations of medical radionuclides such as 225Ac and 213Bi. [ABSTRACT FROM AUTHOR]

Temperature-responsive and electrically conductive doubly filled highly porous poly(N-isopropylacrylamide)/SiO 2 /polyaniline hydrogels were successfully prepared. They contained 2.5–44 wt.% PANI in dry gel and 6 wt.% SiO 2 in the PANI-free part of the dry gel. These materials are of interest as potential actuators (generating movement or pressure change), because of their ultra-fast volume changes, which can be triggered by ohmic- or by induction heating (remote triggering in the latter case), as well as in the function of electrical switches controlled by heating/cooling (shrinking and expanding conductive element). The prepared doubly filled porous gels display reversible and symmetrical response to temperature jumps as fast as 6 s for 75% of the swelling change, and conductivities as high as 74 000 μS/cm. After testing several synthesis approaches, an efficient two-step route was developed, consisting in the impregnation of porous PNIPAm/SiO 2 precursor gels with PANI precursors, which led to a highly selective PANI incorporation into the pore walls (as sub-micrometre-sized irregular and branched filaments). The incorporation of the ‘first filler’, nano-SiO 2 , was crucial in the developed synthesis, which required an ultra-fast T -responsivity of the PANI-free precursor gel. In order to achieve optimal conductivities, the PANI filler was reduced to the emeraldine form using SnCl 2 . Conductivity measurements indicated, that PANI percolation is approached near 20 wt.%, and achieved between 20 and 44 wt.%. At such loadings, PANI also acts as a distinct mechanical reinforcement in the gels. [ABSTRACT FROM AUTHOR]

The assembly of Ag and Au nanoparticles (NPs) into nanoparticulate arrays mediated by terpyridine (tpy), 4'-(2-thienyl)terpyridine (T-tpy), and short α,ω-bis(tpy)oligothiophene ligands has been accomplished at the interface between the Ag or Au NP hydrosol and a solution of the molecular species in dichloromethane. The relationship between the morphology and the optical responses of the arrays has been investigated by advanced methods of TEM (transmission electron microscopy) image analysis and surface plasmon extinction (SPE) spectra. It has been established that the size of islands of closely spaced NPs rather than the average interparticle distance affects the extent of delocalization of the surface plasmon excitations and thus also the SPE spectra. Furthermore, the structure of surface-adsorbate complexes formed in these arrays has been investigated by SERS spectral measurements carried out as a function of the excitation wavelength. Photoinduced charge transfer (CT) transitions from the neutral Ags 0 and Aus 0 adsorption sites on metal NPs to antibonding orbitals of the adsorbates have been identified for Ag/tpy, Ag/T-tpy, Au/tpy, and Au/T-tpy nanoparticulate arrays. Although the surface-adsorbate complexes displaying a photoinduced CT are known for Ag NPs, the Aus 0 surface complexes with this CT are newly reported. Bis(tpy)oligothiophenes were found to be attached to both Ag and Au NPs via the tpy group(s). The match between the interparticle distances within the NP islands and the lengths of the oligomers molecules indicates that the molecules act as interparticle linkers. In this case, unequivocal spectral marker band evidence of the Ags 0 as well as Aus 0 surface complex formation has not been obtained. [ABSTRACT FROM AUTHOR]

Doubly filled nanocomposite poly(N-isopropylacrylamide)-SiO 2 -starch hydrogels were prepared via simultaneous polymerization of N-isopropylacrylamide (NIPAm) and tetramethoxysilane hydrolysis, in the presence of colloid amylopectin starch (4–30 wt.% in dry gel). Besides bulk hydrogels, also highly porous ones were prepared, the latter via solvent freezing during synthesis (cryogels). The branched starch molecules, which interpenetrate PNIPAm, appear to enforce less crosslinked but more regular PNIPAm network with a wider mesh, in place of the irregular one, which is normally obtained in divinyl-crosslinked PNIPAm. The hydroxyl groups of starch form efficient hydrogen bonds to the PNIPAm matrix, as well as to the SiO 2 nanofiller, which in turn also has strong H-bonds to PNIPAm. In bulk gels, a strong synergy of both fillers is clearly observed, leading to a marked increase in moduli, in spite of the wider network mesh. Very distinct is the improvement of tensile properties if starch is incorporated: the elongation at break increases 2 times in porous gels and 3–6 times in bulk ones. The gels’ toughness is also tremendously improved. The porous PNIPAm-SiO 2 -starch gels further display an ultra-fast swelling response to temperature jumps, both deswelling and re-swelling. Interestingly, starch-rich bulk PNIPAm-starch and PNIPAm-SiO 2 -starch gels also display a very fast (and also very extensive) temperature-induced deswelling, while their re-swelling is very slow (as would be expected). This behaviour practically represents a strong ‘one way response’ to temperature jumps. The specific properties of the interface between swollen PNIPAm and starch enable the rapid water escape from the bulk gels, especially if starch-rich domains are present. [ABSTRACT FROM AUTHOR]

Using the distal molar of a minipig as a model, we studied changes in the microstructural characteristics of apatite crystallites during enamel maturation (16-23 months of postnatal age), and their effects upon the mechanical properties of the enamel coat. The slow rate of tooth development in a pig model enabled us to reveal essential heterochronies in particular components of the maturation process. The maturation changes began along the enamel-dentine junction (EDJ) of the trigonid, spreading subsequently to the outer layers of the enamel coat to appear at the surface zone with a 2-month delay. Correspondingly, at the distal part of the tooth the timing of maturation processes is delayed by 3-5 month compared to the mesial part of the tooth. The early stage of enamel maturation (16-20 months), when the enamel coat is composed almost exclusively of radial prismatic enamel, is characterized by a gradual increase in crystallite thickness (by a mean monthly increment of 3.8 nm); and an increase in the prism width and thickness of crystals composed of elementary crystallites. The late stage of maturation (the last two months prior to tooth eruption), marked with the rapid appearance of the interprismatic matrix (IPM) during which the crystals densely infill spaces between prisms, is characterized by an abrupt decrease in microstrain and abrupt changes in the micromechanical properties of the enamel: a rapid increase in its ability to resist long-term load and its considerable hardening. The results suggest that in terms of crystallization dynamics the processes characterizing the early and late stage of mammalian enamel maturation represent distinct entities. In regards to common features with enamel formation in the tribosphenic molar we argue that the separation of these processes could be a common apomorphy of mammalian amelogenetic dynamics in general. [ABSTRACT FROM AUTHOR]

Aqueous dispersions of poly(methacrylic acid)-coated superparamagnetic iron oxide nanoparticles (PMAA@SPIONs) and nanoparticles obtained by adding a layer of double-hydrophilic cationic block polyelectrolyte poly(ethylene oxide)- block -poly(N-methyl-2-vinylpyridinium iodide) (PEO-QP2VP) on PMAA@SPIONs were studied by a combination of static and dynamic light scattering, SAXS, transmission electron microscopy and atomic force microscopy, probing the structure of the SPION aggregates on the lengthscale from 1 to 10 3 nm. Both SALS and AFM results indicate that adding a PEO-QP2VP layer to PMAA@SPIONs decreases the size of SPION aggregates formed in the dispersions. While TEM micrographs show that PEO-QP2VP@PMAA@SPION particles are less apt to form small clusters with the size of several tens nm compared to PMAA@SPION particles, the local clustering has no effect on the power law scattering behavior ( I ( q ) ∼ q −1.4 ) of the SPION dispersions at longer lengthscales (tens to hundreds nm), which reflects mainly polydispersity of the aggregates. [ABSTRACT FROM AUTHOR]

Morphology, macro-, and micromechanical properties of novel poly(urethane-urea)/silica nanocomposites were analyzed by electron microscopy, dynamic mechanical thermal analysis, and microindentation. The studied nanocomposites were based on a poly(urethane-urea) (PUU) matrix filled by nanosilica, and were prepared from waterborne dispersions of PUU (latex) and SiO2. The loading of nano-SiO2 was varied between 0 (neat matrix) and 40 wt% in the dry nanocomposite. The prepared materials were all formally in the rubbery state at room temperature, but they displayed complex elastoviscoplastic behavior, spanning from stiffer elastomeric type to semi-glassy. Because of the employed rigid and highly uniform spherical nanofiller, the materials are of great interest for model microindentation studies. Additionally, because of the polycarbonate-type elastic chains of the PUU matrix, hydrogen bonding in the studied nanocomposites was expected to be rich and diverse, ranging from very strong to weak. In micro- and macromechanical tests, all the elasticity-related properties correlated very strongly. The relations among the properties that related to energy dissipation were complex, and were highly affected by the existence of hydrogen bonding of broadly varied strength, by the distribution patterns of the fine nanofiller, as well as by the eventual locally endured larger deformations during the tests, and the tendency of the materials to cold flow. [ABSTRACT FROM AUTHOR]

The overall need for the preparation of new medicinal radionuclides has led to the fast development of new sorption materials, extraction agents, and separation methods. Inorganic ion exchangers, mainly hydrous oxides, are the most widely used materials for the separation of medicinal radionuclides. One of the materials that has been studied for a long time is cerium dioxide, a competitive sorption material for the broadly used titanium dioxide. In this study, cerium dioxide was prepared through calcination of ceric nitrate and fully characterized using X-ray powder diffraction (XRPD), infrared spectrometry (FT-IR), scanning and transmission electron microscopy (SEM and TEM), thermogravimetric and differential thermal analysis (TG and DTA), dynamic light scattering (DLS), and analysis of surface area. In order to estimate the sorption mechanism and capacity of the prepared material, characterization of surface functional groups was carried out using acid-base titration and mathematical modeling. Subsequently, the sorption capacity of the prepared material for germanium was measured. It can be stated that the prepared material is prone to exchange anionic species in a wider range of pH than titanium dioxide. This characteristic makes the material superior as a matrix in 68Ge/68Ga radionuclide generators, and its suitability should be further studied in batch, kinetic, and column experiments. [ABSTRACT FROM AUTHOR]

This study aims at characterization of porous poly(ε-caprolactone) (PCL) scaffolds prepared by the methods of thermally induced phase separation (TIPS) and TIPS supported by particulate leaching (PL). Both techniques were combined with freeze-drying. Two PCL grades (with different average molecular weight characterized by MFR 6.1 and 1.2 g/10 min) were employed in the fabrication of scaffolds. Three types of salt (sodium chloride) particles were used in the TIPS-PL preparation of the PCL sample: (i) smaller particles (S) measuring 200–315 μm, (ii) larger particles (B) measuring 500–600 μm, and (iii) mixture of S and B particles (S/B = 1/1 wt/wt). The crystallization behavior of the PCL solutions and the thermal properties of scaffolds were investigated by polarized light microscopy (PLM) and differential scanning calorimetry (DSC), respectively. The structural changes of PCL were studied by attenuated total reflectance infrared spectroscopy (ATR-FTIR). The scaffold structure was visualized by means of scanning electron microscopy (SEM) and X-Ray micro-computed tomography (X-ray micro-CT). Furthermore, the density, porosity, water uptake, contact angle and compressive properties of scaffold were investigated. The molecular weight of PCL had an impact on the crystallization of the PCL solutions and thereby on the crystallinity of scaffolds and the morphology of pore walls formed during TIPS. Sodium chloride grains had an influence on the pore size and overall morphology of foam scaffolds prepared by TIPS-PL. The addition of NaCl decreased significantly the density and compressive properties and increased the porosity and water uptake of scaffolds. • Porous PCL scaffolds prepared by the methods of TIPS and TIPS-PL were compared. • The crystallization behaviour of the PCL solutions were investigated. • The crystallinity of scaffolds and the morphology of pore walls were described. • Structure-property relationships in PCL porous scaffolds were studied. [ABSTRACT FROM AUTHOR]

Metal nanostructure-treated polymers are widely recognized as the key material responsible for a specific antibacterial response in medical-based applications. However, the finding of an optimal bactericidal effect in combination with an acceptable level of cytotoxicity, which is typical for metal nanostructures, prevents their expansion from being more significant so far. This study explores the possibility of firmly anchoring silver nanoparticles (AgNPs) into polyetherether ketone (PEEK) with a tailored surface morphology that exhibits laser-induced periodic surface structures (LIPSS). We demonstrated that laser-induced forward transfer technology is a suitable tool, which, under specific conditions, enables uniform decoration of the PEEK surface with AgNPs, regardless of whether the surface is planar or LIPSS structured. The antibacterial test proved that AgNPs-decorated LIPSS represents a more effective bactericidal protection than their planar counterparts, even if they contain a lower concentration of immobilized particles. Nanostructured PEEK with embedded AgNPs may open up new possibilities in the production of templates for replication processes in the construction of functional bactericidal biopolymers or may be directly used in tissue engineering applications. [ABSTRACT FROM AUTHOR]

Due to the simple one-step preparation method and a promising application in biomedical research, amphiphilic gradient copoly(2-oxazoline)s are gaining more and more interest compared to their analogous block copolymers. In this work, the curcumin solubilization ability was tested for a series of amphiphilic gradient copoly(2-oxazoline)s with different lengths of hydrophobic side-chains, consisting of 2-ethyl-2-oxazoline as a hydrophilic monomer and 2-(4-alkyloxyphenyl)-2-oxazoline as a hydrophobic monomer. It is shown that the length of the hydrophobic side-chain in the copolymers plays a crucial role in the loading of curcumin onto the self-assembled nanoparticles. The kinetic stability of self-assembled nanoparticles studied using FRET shows a link between their integrity and cellular uptake in human glioblastoma cells. The present study demonstrates how minor changes in the molecular structure of gradient copoly(2-oxazoline)s can lead to significant differences in the loading, stability, cytotoxicity, cellular uptake, and pharmacokinetics of nano-formulations containing curcumin. The obtained results on the behavior of the complex of gradient copoly(2-oxazoline)s and curcumin may contribute to the development of effective next-generation polymeric nanostructures for biomedical applications. [ABSTRACT FROM AUTHOR]

We report on the synthesis of poly(N-isopropyl acrylamide)- block -poly( n -butyl acrylate) (PNIPAm- b -PnBA) amphiphilic block copolymers and their temperature-responsive self-assembly behavior in aqueous solution. Well-defined PNIPAm- b -PnBA copolymers have been synthesized by a two-step RAFT polymerization scheme. The self-assembly behavior was studied by means of static and dynamic light scattering, 1 H NMR and fluorescence spectroscopy and transmission electron microscopy. The results show that already below the lower critical solution temperature (LCST) of PNIPAm, association of the PNIPAm blocks with hydrophobic dodecyl end groups of the charge transfer agent leads to the formation of loose aggregates of PNIPAm- b -PnBA micelles, the size and density of which increase with the increasing length of the PNIPAm block. The collapse of the PNIPAm blocks above the LCST leads to the decrease of the aggregates’ size and the increase of their density, but the collapsed PNIPAm chains do not allow for interpenetration of the micellar shells and no further aggregation occurs. [ABSTRACT FROM AUTHOR]

In the last two decades, the importance of nanomaterials in modern technologies has been unquestionable. Metal nanoparticles are frequently used in many areas of science and technology, delivering unprecedented improvements to properties of the conventional materials. This work introduces an effective tool for preparing a highly enriched poly (ethylene terephthalate) (PET) surface with silver nanoparticles, firmly immobilized in the same surface area on polymer. We showed that besides pristine polymer, this approach may be successfully applied also on laser pre-treated PET with laser-induced periodic surface structures. At the same time, its final nanostructure may be effectively controlled by laser fluence applied during the immobilization process. [ABSTRACT FROM AUTHOR]

Polyurea protective coatings have gained large interest from research and application in coating and gel polyelectrolyte areas due to their durability, excellent thermal, and mechanical stability, and the possibility of cure without the use of any catalyst or solvent. In this study, we address a chemical mechanism of the aspartate amine–isocyanate cure that involves an unexpected transition of urea bonds into hydantoin bonds. Three aspartic esters (ASPEs) with varying chemical structures were used to study model high-solid (≥60 wt.-% solid content) polyurea coatings. Two linear aliphatic ASPEs with flexible backbones that were prepared using the aza-Michael addition, and a commercial cycloaliphatic aspartic ester (Desmophen® NH 1420) were used as polyurea-based network precursors and were crosslinked with the plant-based tri-isocyanate Desmodur® eco N 7300. The coatings were cured under ambient conditions, and the effect of the molecular structure, chain length of ASPE, cure time, and the simultaneous chemical crosslinking and solvent evaporation on the coating properties were thoroughly investigated. The chemical changes that occurred throughout the film depths were analyzed by FTIR and Raman confocal microscopy. The study revealed the inherent transformation of urea bonds to substituted hydantoin rings. The intensity of transformation depended on the mobility of the polyurea network chain segments in ASPEs. The thermal and mechanical properties characterized by DSC, TGA, uniaxial tensile test, and microindentation hardness test showed the softening effect of the hydantoin group on the networks effective within weeks after the NCO primary cure. [Display omitted] • Newly synthesized bis-aspartate esters crosslinked with a polyisocyanate at RT provided strong, thermally resistant polyurea coatings. • The polyurea coatings exhibited gradients of cure perpendicular to the substrate driven by the negative difference T cure – T g. • In PU-ASPE networks, the urea groups transformed into intramolecular cycles, the hydantoin rings. • The hydantoin cycles caused mild increase of mobility in the PU-ASPE networks. [ABSTRACT FROM AUTHOR]

Polyelectrolyte–surfactantcomplexes (PE–S) formedby double hydrophilic cationic polyelectrolyte poly[3,5-bis(dimethylaminomethyl)-4-hydroxystyrene]-block-poly(ethylene oxide) (NPHOS-PEO) and anionic surfactantsodium dodecyl sulfate (SDS) in acidic aqueous solutions were studiedby light scattering, SAXS, and scanning transmission electron microcopyin the environmental mode (wet-STEM) for various stoichiometric ratiosbetween the numbers of SDS anions and dimethylaminomethyl groups ofNPHOS in the complex. The obtained results show that the NPHOS-PEO/SDSsystem behaves differently from other systems of double hydrophilicblock polyelectrolyte and oppositely charged ionic surfactant becauseit forms water-insoluble PE–S for compositions close to thezero net charge of the complex. This phase separation occurs, insteadof the PE–S rearrangement to core–shell particles, whichis hindered due to conformational rigidity of the NPHOS blocks. Forthe surfactant amounts below and above the precipitation region, largespherical aggregates and their clusters are present in the solution.SAXS measurements indicate that although the NPHOS-PEO/SDS systemdoes not form the core–shell particles with the NPHOS/SDS coreand the PEO shell as other PE–S of double hydrophilic polyelectrolytes,the aggregates contain domains of closely packed surfactant micelleswhich bind to both NPHOS polyelectrolyte blocks and PEO blocks. [ABSTRACT FROM AUTHOR]

Abstract: Swelling and dynamic mechanical behavior in a broad frequency range of homogeneous and porous poly(2-hydroxyethyl methacrylate) gels were studied in relation to their matrix structure, gel morphology and nature of the swelling medium. Very lightly cross-linked gels showed up relatively large mechanical losses caused by slow relaxation of hydrophobic physical associates still proceeding at frequency 10−3 Hz. The macroporous gels of fused-spheres type morphology contained many dangling aggregates not bearing the stress which caused concentration of the stresses in the load bearing paths through the matrix. This is the reason for the sudden drop of storage modulus. In the α-relaxation region, the loss factors for homogeneous and porous gels merged into a single master curve. Reswelling of gels in a poor solvent caused a decrease of the swelling degree and shifted their α-relaxation to lower frequencies; reswelling in good solvent shifted the maximum of α-relaxation to higher frequencies. [Copyright &y& Elsevier]

The influence of the matrix crystallization on the coalescence of the dispersed phase particles, in quiescent immiscible polymer blends, is a topic that is scientifically addressed scarcely. The coarsening of the phase structure that is induced by the matrix crystallizing domains was studied using the well-established system comprising a polypropylene and an ethylene-propylene rubber (PP/EPR blends). This subject is of great importance as the effectiveness in the toughening of PP is directly determined by the EPR particle size. Cooling experiments were commenced for resolving the correlation among the imposed cooling conditions, the formed matrix crystalline morphology, and the coalescence of the dispersed phase particles. A confirmation of the profound effect of the PP crystallization on the coalescence of EPR particles was undoubtedly obtained. The contribution of the crystallization to the coalescence of the dispersed phase particles is largest at a finite rate of cooling. A thorough discussion regarding the observed effects, encompassing a potential rejection or an engulfing of the dispersed phase particles by the growing crystallites, was undertaken. [ABSTRACT FROM AUTHOR]

Abstract: Fast thermoresponsive porous hydrogels based on the PNIPAM–silica nanocomposite were prepared and optimized in order to obtain increased force (pressure) response to temperature stimuli. This was achieved by increasing pore wall thickness via changing the monomers concentration during the hydrogels’ cryogenic synthesis. The mechanically strong and compact pore structure of the best gel made it possible to increase the force (pressure) response 3 times and the shear modulus 4 times, while the volume ratio of swollen to deswollen state remained unchanged, and the kinetics of the T-response was only moderately slower than in the case of the analogous ultra-fast responsive soft gels. The porous structure of the hydrogels (SEM), the dispersion and particle size of the nanofiller in the pore walls (TEM), as well as the swelling behavior and time-resolved force response to T-change are discussed in this work. [Copyright &y& Elsevier]

Abstract: The effect of polydispersity on dilute solution properties and microphase separation of polydisperse high-molecular-weight (M w >105 gmol−1) polystyrene-block-poly(styrene-co-acrylonitrile) diblock copolymers, PS-block-P(S-co-AN), was studied in this work. For experiments, a series of diblock copolymers with variable weight fractions of acrylonitrile units (w AN =0.08–0.29) and length of block P(S-co-AN) was synthesized using nitroxide-mediated radical polymerization (NMP) technique, namely, by chain extension of nitroxide-terminated polystyrene (PS-TEMPO). According to light scattering and viscometry measurements in dilute tetrahydrofuran (THF) solutions the studied diblock copolymers assumed random coil conformation with the values of characteristic structure factor R g/R h =1.50–1.76. It was found that polydisperse diblock copolymers being in strong segregation limit (SSL) self-assembled into microphase-separated ordered morphologies at ordinary temperature. The long periods of lamellar microdomains were larger compared to theoretical predictions for hypothetical monodisperse diblock copolymers. It was demonstrated by means of SAXS and TEM that a transition from a lamellar (LAM) to irregular face-centered-cubic (FCC) morphology occurred with increasing volume fraction of P(S-co-AN) block. [Copyright &y& Elsevier]

Abstract: The interaction of repetitive nanosecond laser pulses with near-spherical gold nanoparticles, dispersed in an aqueous ambient and having various mean sizes, was studied for two different wavelengths 355 and 532nm and various energies per pulse. From the in situ surface plasmon (SP), extinction measurements combined with ex situ TEM studies of the irradiated hydrosols, we conclude that the process of laser-induced fragmentation is cumulative with increasing number of subsequent pulses. Interestingly, irradiation of all parent hydrosols having different mean particle sizes (except of that one containing nanoparticles with the mean diameter of 5nm) with laser pulses of the 532nm wavelength and the same energy per pulse absorbed in the hydrosol resulted into hydrosols containing nanoparticles of very similar reduced mean sizes and size distributions. On the other hand, for the parent nanoparticle hydrosol with the initial mean particle diameter below 5nm, a small increase of the mean particle size has been detected after irradiation with pulses of the same wavelength. The mean sizes of Au nanoparticles fragmented by 355nm pulses were generally smaller than those fragmented at 532nm. [Copyright &y& Elsevier]

Industrially important properties of wood can be changed due to the modification of birch wood (Betula pendula L.) after the process of thermal treatment with saturated water steam. The birch wood was modified by saturated water steam at 125 ± 2.5 °C for 8 hours and at a pressure of 0.18 MPa. The water contact angle of steam-treated birch wood increased from 42.1° (for untreated birch wood) to 52.4° (for steam-treated birch wood), and the stability of water drop on steam-treated birch wood surface increased. FTIR spectra showed an increase in C=O and glycoside bonds concentration on the surface of steam-treated birch wood, but the concentration of C-O-C groups decreased. XPS measurements confirmed that the concentration of oxygen as well as C=O and C-O-O groups on the surface of steamtreated birch wood showed an increment in comparison with the native wood sample. SEM micro photos confirmed the minor changes of birch wood cells due to the action of saturated water steam modification. [ABSTRACT FROM AUTHOR]

Poly(2-hydroxyethyl methacrylate) (PHEMA) crosslinked with ethylene dimethacrylate (EDMA) or N,O-dimethacryloylhydroxylamine (DMHA) was obtained in the form of slabs by bulk radical polymerization. Two porosity-inducing methods were investigated, phase separation using a low-molecular-weight porogen and a salt-leaching technique using NaCl and saccharose. Compared with the phase separation, the salt-leaching created open porous structures with voids of the size and shape of crystallites. To address its potentials in the context of stem cell therapies, undifferentiated mouse embryonic stem cells D3 (ES D3 cells) were seeded on the slabs and analyzed for the ability to grow on different types of non-degradable and/or degradable porous PHEMA hydrogels. The cells were able to proliferate only on PHEMA crosslinked with EDMA or 2 wt% DMHA. In order to assess the effect of gelatin, which is routinely used for ES cell cultures, PHEMA slabs were soaked in gelatin solutions and compared the number of cells on gelatin-treated and untreated slabs 4 days after cell seeding. Surprisingly, the number of cells was only slightly higher on gelatin-treated slabs. [Copyright &y& Elsevier]

Epoxy-polyhedral oligomeric silsesquioxane (POSS) nanocomposites were prepared by incorporating POSS nanofiller into the epoxy-amine network. The monofunctional epoxy-POSS monomer or nonfunctional octaphenyl POSS unit were applied to reinforce the epoxy network by producing the nanocomposite with chemically bound pendant POSS or physically admixed POSS. The combination of reactive and unreactive POSS, leads to a synergistic effect and to the most efficient reinforcement of the epoxy network. Both polymer-POSS and POSS–POSS interactions are present in the system and lead to a strong physical crosslinking through the path polymer-bound POSS-unbound POSS domain. The nanocomposite was modified by incorporation of the thermoreversible Diels–Alder (DA) type network. The produced interpenetrating network composed of the irreversible reinforced epoxy and the reversible DA networks exhibits an efficient self-healing capability. This strong nanocomposite, showing a modulus of 800 MPa at room temperature, was healed with an efficiency of 61%. The developed stiff nanocomposite is shown to be a promising material because self-healing of strong thermosets is still a big challenge. With the increasing content of POSS nanofiller and heterogeneity of the nanocomposite, however, the healing efficiency diminishes. The insufficient contact of crack surfaces due to involved inhomogeneities results in a worse sealing of the material crack. [ABSTRACT FROM AUTHOR]

This paper presents an investigation of CO2 capture ability of ordered carbon (CMK-3) composed of a two-dimensional hexagonal array of turbostratic carbon rods of 19.7 nm and 8.7 nm in diameter with interstitial mesopores and non-restricted micropores in the rods at atmospheric pressure. The CMK-3 carbon had a mesopore mean inner diameter of 3.42 nm and a microporous structure with modus of pore diameter of 1.30 nm. Despite the fact that the mesopores did not directly take part in CO2 adsorption at atmospheric pressure, the carbon material exhibited good performance in CO2 capture, adsorbing 1.70 mmol g−1 and 1.07 mmol g−1 in the micropores at 293 and 323 K, respectively. The open mesoporous channel structure with regular architecture provided easy accessibility of the micropores in the carbon walls that formed the structure of CMK-3 carbon. Enhancement of accessibility improved the molecular transport of CO2, providing advantageous kinetics compared to purely microporous materials. The adsorption rate obtained from kinetics studies were decreasing with gas pressure increase in the system and were increasing with temperature increase. The ordered mesoporous-microporous carbon structure allowed excellent reversibility, regeneration ability and high selectivity of CO2 over N2 molecules. Graphical abstarct: [ABSTRACT FROM AUTHOR]

[Display omitted] Hydrophobic blocks of amphiphilic block copolymers often form glassy micellar cores at room temperature with a rigid structure that limits their applications as nanocapsules for targeted delivery. Nevertheless, we prepared and analyzed core/shell micelles with a soft core, formed by a self-assembled block copolymer consisting of a hydrophobic block and a polycation block, poly(lauryl acrylate)- block -poly(trimethyl-aminoethyl acrylate) (PLA-QPDMAEA), in aqueous solution. By light and small-angle neutron scattering, by transmission electron microscopy and by fluorescence spectroscopy, we showed that these core/shell micelles are spherical and cylindrical with a fluid-like PLA core and a positively charged outer shell and that they can encapsulate and release hydrophobic solutes. Moreover, after mixing these PLA-QPDMAEA core/shell micelles with another diblock copolymer, consisting of a hydrophilic block and a polyanion block, namely poly(ethylene oxide)- block -poly(methacrylic acid) (PEO-PMAA), we observed the formation of novel vesicle-like multicompartment structures containing both soft hydrophobic and interpolyelectrolyte (IPEC) layers. By combining small-angle neutron scattering with self-consistent field modeling, we confirmed the formation of these complex vesicle-like structures with a swollen PEO core, an IPEC inner layer, a PLA soft layer, an IPEC outer layer and a loose PEO corona. Thus, these multicompartment micelles with fluid and IPEC layers and a hydrophilic corona may be used as nanocapsules with several tunable properties, including the ability to control the thickness of each layer, the charge of the IPEC layers and the stability of the micelles, to deliver both hydrophobic and multivalent solutes. [ABSTRACT FROM AUTHOR]

Magnetic maghemite (γ-Fe2O3) nanoparticles obtained by a coprecipitation of iron chlorides were dispersed in superporous poly(2-hydroxyethyl methacrylate) scaffolds containing continuous pores prepared by the polymerization of 2-hydroxyethyl methacrylate (HEMA) and ethylene dimethacrylate (EDMA) in the presence of ammonium oxalate porogen. The scaffolds were thoroughly characterized by scanning electron microscopy (SEM), vibrating sample magnetometry, FTIR spectroscopy, and mechanical testing in terms of chemical composition, magnetization, and mechanical properties. While the SEM microscopy confirmed that the hydrogels contained communicating pores with a length of ≤2 mm and thickness of ≤400 μm, the SEM/EDX microanalysis documented the presence of γ-Fe2O3 nanoparticles in the polymer matrix. The saturation magnetization of the magnetic hydrogel reached 2.04 Am2/kg, which corresponded to 3.7 wt.% of maghemite in the scaffold; the shape of the hysteresis loop and coercivity parameters suggested the superparamagnetic nature of the hydrogel. The highest toughness and compressive modulus were observed with γ-Fe2O3-loaded PHEMA hydrogels. Finally, the cell seeding experiments with the human SAOS-2 cell line showed a rather mediocre cell colonization on the PHEMA-based hydrogel scaffolds; however, the incorporation of γ-Fe2O3 nanoparticles into the hydrogel improved the cell adhesion significantly. This could make this composite a promising material for bone tissue engineering. [ABSTRACT FROM AUTHOR]

In this work, doubly physically crosslinked hydrogels were synthesized, based on poly(N-isopropylacrylamide) containing 10 mol% of methacrylate co-monomer, in which nano-platelets of hectorite clay acted as the primary strong physical crosslinker, and trivalent cations La3+, Fe3+, and Al3+ as an additional dynamic one. Due to their excellent mechanical and tensile properties, such gels might be of interest as advanced structural materials for soft robotics. Of especial scientific interest was the comparison of the seemingly similar trivalent cations embedded in analogous gels, where their different bonding to carboxylate made dramatic differences concerning the material properties: La3+—purely electrostatic and highly dynamic bonding, Fe3+—with tendency to coordination-covalent-, and Al3+—with a rather covalent bonding. The cations incorporated into the hydrogels caused a marked, or even very strong improvement of tensile toughness, which in case of La3+ occurred without reducing the extensibility. All the cations expectedly raised the modulus: the effect was most pronounced with Al3+, which tends to covalent bonding. Most importantly, all the cations improved the kinetics of internal self-healing (self-recovery) of the gels, which was fastest with the dynamically (purely electrostatically) bonding La3+ (complete recovery of properties in 1 h). All the cations were incorporated via impregnation of precursor gels. An original synthesis aspect was, that the impregnation was conducted for a brief period of time, which was found necessary to achieve maximum modulus (the modulus dropped again at longer times). In this way, a non-stoichiometric (usually sub-stoichiometric) amount was incorporated, which made a subsequent extraction of cation excess unnecessary. Additionally, the non-stoichiometry helped the self-healing (network reorganization), which was most striking in case of the rather covalently bonding Al-impregnated gel. [ABSTRACT FROM AUTHOR]

[Display omitted] • Innovative polymer coatings on anodes improve electromediated biofilm eradication. • Coatings catalyze ROS generation or convert hydrophobic surfaces to bactericidal polycations. • Promising efficacy against Staphylococcus aureus biofilms demonstrated. • Addressing critical challenge in medical field: biofilm-associated infections. The formation of biofilm involves cell aggregation and adherence, enveloped by a self-produced extracellular matrix. In the medical domain, biofilm-associated infections pose significant challenges, especially concerning implants. This investigation focuses on enhancing electromediated bacterial biofilm eradication through polymer coatings on the anode. These coatings catalyze reactive oxygen species (ROS) generation or convert hydrophobic coatings to bactericidal hydrophilic polycations, detaching the biofilms that are predominantly polyanionic. The first approach employs a metallized polytetrathienylporphyrin layer with ROS catalytic capability, while the second involves an insoluble hydrophobic polyamide, which, upon oxidation, transforms into a bactericidal hydrolytically degradable polycation. Both approaches show promising efficacy in augmenting electromediated Staphylococcus aureus biofilm destruction. [ABSTRACT FROM AUTHOR]

Multimodal imaging, integrating several modalities including down- and up-conversion luminescence, T1- and T2(T2*)-weighted MRI, and CT contrasting in one system, is very promising for improved diagnosis of severe medical disorders. To reach the goal, it is necessary to develop suitable nanoparticles that are highly colloidally stable in biologically relevant media. Here, hydrophilic poly(N,N-dimethylacrylamide-N-acryloylglycine methyl ester)-alendronate-[P(DMA-AGME)-Ale]-coated Gd(Tb)F3:Tb3+(Gd3+),Yb3+,Nd3+ nanoparticles were synthesized by a coprecipitation method in ethylene glycol (EG) followed by coating with the polymer. The particles were tho-roughly characterized by a dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), X-ray energy dispersive spectroscopy (EDAX), selected area electron diffraction (SAED), elemental ana-lysis and fluorescence spectroscopy. Aqueous particle dispersions exhibited excellent colloidal stability in water and physiological buffers. In vitro toxicity assessments suggested no or only mild toxicity of the surface-engineered Gd(Tb)F3:Tb3+(Gd3+),Yb3+,Nd3+ particles in a wide range of concentrations. Internalization of the particles by several types of cells, including HeLa, HF, HepG2, and INS, was confirmed by a down- and up-conversion confocal microscopy. Newly developed particles thus proved to be an efficient contrast agent for fluorescence imaging, T1- and T2(T2*)-weighted magnetic resonance imaging (MRI), and computed tomography (CT). [ABSTRACT FROM AUTHOR]

Polyaniline–silver cryogels were prepared by a single-step cryopolymerization with a mixed oxidant consisting of ammonium peroxydisulfate and silver nitrate for in situ incorporation of silver particles. The macroporous structure of the materials and successful introduction of silver microparticles were confirmed by scanning electron microscopy paired with energy-dispersive spectroscopy. Changing of the silver nitrate content in the initial oxidant mixture was shown to be a facile way for controlling silver particles load in the resulting cryogels with a maximum achieved value of 25 wt%. Vibrational spectroscopy showed that the cryogels prepared using higher silver nitrate concentration contained more aniline oligomers which led to the moderate decrease in their conductivity and tensile modulus. Nevertheless, polyaniline–silver cryogels with the highest load of silver had a good conductivity (0.33 S cm–1) and mechanical stability making it a promising material for electrochemical and antibacterial applications. [ABSTRACT FROM AUTHOR]

In the after-fire restoration of the buildings belonging to the culture heritage, the use of salvaged scorched wood elements is desirable but often leading to the long-term malodorous, irritating, or unhealthy emissions. To reduce them while preserving the authenticity as much as possible, the micro-abrasive cleaning method was tested on samples from a burned-down historical wooden building. Volatile compounds in the headspace of the samples were analyzed by gas chromatography coupled with mass spectrometry. The chromatograms from above the scorched wood before cleaning showed a number of volatile products, mostly typical for wood degradation. After the removal of ca 2 mm layer of the scorched wood, the profile of volatiles was almost identical to that above the intact sample, and as reported for neat wood. The results of our study demonstrate how the authenticity of wood elements in buildings restored after fire can be increased without compromising the air quality. [ABSTRACT FROM AUTHOR]