Search

Layer-by-layer (LbL) polyelectrolyte coatings are intensively studied as reservoirs of bioactive proteins for modulating interactions between biomaterial surfaces and cells. Mild conditions for the incorporation of growth factors into delivery systems are required to maintain protein bioactivity. Here, we present LbL films composed of water-soluble

Introducing polymerizable monomers into a binary hexagonal lyotropic liquid crystalline (LLC) template is a straightforward way for retaining the nanostructure but will decrease attractive intra- and inter- aggregate interactions. It is therefore crucial to understand the interfacial interactions at nanoscale after introducing the monomers but prior to polymerization. Herein, active species, poly (ethylene glycol) diacrylate (PEGDA) and 2-hydroxyethyl methacrylate (HEMA), were introduced into hexagonal LLC of dodecyl trimethylammonium bromide and water to explore the structural variables, dimensional stability, and dynamic property. At a proper volume ratio of PEGDA/HEMA (1/4), the system presents excellent homogeneity with a higher dimensional stability and lower dynamic property from rheological assessments, thereby achieving robust, free-standing, and transparent membranes after photo-polymerization. The unique property of the system also lies in the much lower order–disorder transition temperature (45 °C) that facilitates the reorientation of mesochannels. They are in contrast inaccessible for the ternary system only with PEGDA, though the nanostructure for both systems could be retained. An insight into subtle variations in these parameters allows us to prepare a polymerizable template possessing higher dimensional stability and suitable flexibility via molecular design, thereby enabling simultaneous structural alignment and retention for the development of functional nanomaterials.

The use of fluorinated contrast agents in magnetic resonance imaging (MRI) facilitates improved image quality due to the negligible amount of endogenous fluorine atoms in the body. In this work, we present a comprehensive study of the influence of the amphiphilic polymer structure and composition on its applicability as contrast agents in 19F MRI. Three series of novel fluorine-containing poly(2-oxazoline) copolymers and terpolymers, hydrophilic-fluorophilic, hydrophilic-lipophilic-fluorophilic, and hydrophilic-thermoresponsive-fluorophilic, with block and gradient distributions of the fluorinated units, were synthesized. It was discovered that the CF3 in the 2-(3,3,3-trifluoropropyl)-2-oxazoline (CF3EtOx) group activated the cationic chain end, leading to faster copolymerization kinetics, whereby spontaneous monomer gradients were formed with accelerated incorporation of 2-methyl-2-oxazoline or 2-n-propyl-2-oxazoline with a gradual change to the less-nucleophilic CF3EtOx monomer. The obtained amphiphilic copolymers and terpolymers form spherical or wormlike micelles in water, which was confirmed using transmission electron microscopy (TEM), while small-angle X-ray scattering (SAXS) revealed the core-shell or core-double-shell morphologies of these nanoparticles. The core and shell sizes obey the scaling laws for starlike micelles predicted by the scaling theory. Biocompatibility studies confirm that all copolymers obtained are noncytotoxic and, at the same time, exhibit high sensitivity during in vitro 19F MRI studies. The gradient copolymers provide the best 19F MRI signal-to-noise ratio in comparison with the analogue block copolymer structures, making them most promising as 19F MRI contrast agents.

In this article, we examined the state of fullerene C60 in toluene and its mixtures with acetonitrile in both diluted, (4.0 to 6.3)×10−6 M, and concentrated, (0.23 to 1.9)×10−3 М solutions, prepare...

Ionic liquid 1-butyl-3-methylimidazolium chloride (bmimCl) is a widely applied solvent for cellulose. In this work, we studied the crystallization behavior of bmimCl in the presence of cellulose, a...

The application of nanofillers (NFs) in multicomponent polymer systems is accompanied by important structure-directing effects that are more marked in partially miscible systems, such as polymer-modified epoxy. This study deals with rubber-modified epoxy using different combinations of GO and amine-terminated butadiene-acrylonitrile copolymer (ATBN), including in situ and pre-made grafting. Moreover, GO grafted via planar epoxy groups or solely edge-localized carboxyls was used. It is shown that the grafted ATBN chains promote the assembly of GO-g-ATBN into nacre-mimicking lamellar structures instead of usual exfoliation in thermoplastics. This complex structure of elastically embedded GO leads to the best mechanical performance. It is obvious that a small concentration of the grafted polymer exceeds the contribution of a higher concentration of separately added ATBN. The results highlight the important effect of the degree of grafted chains and geometry of the internal structure of the self-assembled arrays and their effect on the mechanical performance.

This paper reports an original nonstandard green concept to obtain TiO2 microrods with polyhedral densely stacked 3D nanovoids prepared via the heat treatment of a hydrogen titanate. The intermediate hydrogen titanate was synthesized by a solid-liquid-solid (SLS) route from an ammonia-saturated aqueous solution of TiOSO4 at 0 °C. The effect of the postgrowth thermal annealing procedure to remove ice (water) and the proposed mechanism to explain the underlying transitions from the intermediate precursor to nanostructured TiO2 microrods with stacked 3D nanovoids were investigated. The small-angle X-ray scattering (SAXS) analysis indicates that at temperatures above 500 °C, the release of confined ice (water) takes place, which leads to the creation of self-assembled polyhedral nanovoids open to the surface. Their size ranges from 5 to 78 nm in both length and width, with a depth of ~3.88 nm. The first use of these stacked 1D TiO2 microrods as the working electrode in a photoelectrochemical (PEC) cell for water splitting is demonstrated. The estimated value of ζ-potential depends on both annealing temperature and crystallite size. Anatase sample 1D TiO/800 with ζ-potential (−29.1) mV and average crystallite size ~68 nm was observed to be highly stable in aqueous suspension. The SLS method yields low-cost 1D TiO2 materials possessing high photoreactivity with water. The PEC measurements indicate that three-dimensional hollow structures with a controlled geometry via patterned 1D TiO2 surface are promising materials for hydrogen generation from water splitting.

This work studies the influence of dip-coating parameters on self-assembly in ultra-thin films of asymmetric polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) copolymers from a 1-chloropentane solution using a combination of several experimental techniques. Small-Angle X-ray Scattering, Atomic Force Microscopy, Grazing Incidence Small Angle X-ray Scattering and Transmission Electron Microscopy were used to characterize the fabricated films. We have shown a facile fabrication route to smooth films with a wide range of thicknesses. Arranged domains of P4VP oriented perpendicularly to the substrate were observed. The domain sizes and spacing varied in the range from 13 up to 35 nm and from 39 to 115 nm, respectively.

The preparation of materials with aligned porosity in the nanometer range is of technological importance for a wide range of applications in molecular filtration, biomaterials and catalysis. Herein we present the advantages offered by cryo – lyophilisation technique as a smart and green non-standard concept to produce dense regular polyhedral nanocavities inside the 2D TiO2 nanosheets. Hierarchical morphologies of nanocavities start to appear at temperature higher than 800 °C and are strongly influenced by polymorph TiO2 evolution competing reactions. The small angle X-ray scattering (SAXS) analysis confirms self-assembled 3D nanocavities with size range from 5 to 10 nm in both length and width, and depth ˜3.6 nm formed after realising of the confined ice-water. It was found that nanocavities enhance significantly the absorption properties of TiO2 in the UV region, thereby providing a new approach to increase the photoreactivity of 2D TiO2 nanosheets. The annealed precursors containing aqueous solution of peroxo polytitanic acid (PPTA) at 800 °C exhibited the highest photoactivity in degrading bisphenol A (BPA) due to evenly distributed nanocavities inside single anatase TiO2 nanocrystals interconnected and aligned onto the 2D TiO2 nanosheet arrays.

Adsorption of CO2 on three-dimensionally ordered micromesoporous carbon with a spherical pore structure has been studied using gravimetric and manometric analyses. Adsorptive properties were compared with activated carbon and nanostructured carbon materials such as carbon nanotubes, zeolitic-imidazolate framework-derived carbon, carbon nanohorns and ordered mesoporous carbon materials. The regular spherical pores of 14–15 nm diameter with a large pore volume of 3.4 cm3 g−1 provided a very high CO2 adsorption capacity exceeding the compared carbon materials at high gas pressures (≥4 MPa and room temperature). A strong increase in the isosteric heat of CO2 adsorption with increasing surface coverage indicates that high pressure adsorption was predominantly controlled by strong quadrupole moment interactions between CO2 molecules and less intensive interactions of CO2 with the mesoporous surface. Micropores in the walls of the main spherical mesopores, with a pore volume of 0.17 cm3 g−1, provided good CO2 adsorption properties at atmospheric pressure, characterized by rectilinear isotherms and a predominant surface coverage mechanism. Analysis of the strength of CO2 interaction with the carbon adsorbent and a kinetic study of CO2 adsorption revealed excellent CO2 adsorption-desorption reversibility.

The use of fluorinated contrast agents in magnetic resonance imaging (MRI) facilitates improved image quality due to the negligible amount of endogenous fluorine atoms in the body. In this work, we present a comprehensive study of the influence of the amphiphilic polymer structure and composition on its applicability as contrast agents in

Graphene oxide (GO) has high potential for grafting of polymer chains. This mostly enhances exfoliation or controls structure-directing effects in thermoplastic blends, whereas various complex arrays may be formed in the case of epoxy thermosets. This study reveals that the structure of these arrays is markedly influenced by parameters of grafted polymer chains and geometry of grafting. The best-balanced properties were found for nacre-mimicking lamellar arrays with an important role of internal structure and elasticity of grafted chains. Beneficial is s relatively thick “elastic interlayer” of grafted butadiene‐acrylonitrile copolymer with toughening effect comparable to much higher content of free polymer addition.

Physically crosslinked low-temperature elastomers were prepared based on linear polydimethylsiloxane (PDMS) elastic chains terminated on both ends with mesogenic building blocks (LC) of azobenzene type. They are generally (and also structurally) highly different from the well-studied LC polymer networks (light-sensitive actuators). The LC units also make up only a small volume fraction in our materials and they do not generate elastic energy upon irradiation, but they act as physical crosslinkers with thermotropic properties. Our elastomers lack permanent chemical crosslinks&mdash, their structure is fully linear. The aggregation of the relatively rare, small, and spatially separated terminal LC units nevertheless proved to be a considerably strong crosslinking mechanism. The most attractive product displays a rubber plateau extending over 100 &deg, C, melts near 8 &deg, C, and is soluble in organic solvents. The self-assembly (via LC aggregation) of the copolymer molecules leads to a distinctly lamellar structure indicated by X-ray diffraction (XRD). This structure persists also in melt (polarized light microscopy, XRD), where 1&ndash, 2 thermotropic transitions occur. The interesting effects of the properties of this lamellar structure on viscoelastic and rheological properties in the rubbery and in the melt state are discussed in a follow-up paper (&ldquo, Part II&rdquo, ). The copolymers might be of interest as passive smart materials, especially as temperature-controlled elastic/viscoelastic mechanical coupling. Our study focuses on the comparison of physical properties and structure&ndash, property relationships in three systems with elastic PDMS segments of different length (8.6, 16.3, and 64.4 repeat units).

The singlet fission (SF) process discovered in bis(thienyl)diketopyrrolopyrroles (TDPPs) can boost their potential for photovoltaics (PV). The crystal structures of TDPP analogs carrying n-hexyl, n-butyl, or 2-(adamant-1-yl)ethyl substituents are similar, but contain increasingly slipped stacked neighbor molecules. The observed SF rate constants, kSF , (7±4), (9±3) and (5.6±1.9) ns-1 for thin films of the three compounds, respectively, are roughly equal, but the triplet quantum yields vary strongly: (120±40), (160±40) and (70±16), respectively. The recent molecular pair model reproduces the near equality of all three kSF at the crystal geometries and identifies all possible pair arrangements in which SF is predicted to be faster, by up to two orders of magnitude. However, it is also clear that the presently non-existent ability to predict the rates of processes competing with SF is pivotal for providing a guide for efforts to optimize the materials for PV.

The aliphatic polycarbonate based polyurethanes (PU) from poly(hexamethylene) carbonate diol (PC), hexamethylenediisocyanate and hexanediol were synthesized, characterized and designed as promising self healing polymers. The symmetrical linear PU structure containing the hexamethylene sequences results in a high degree of ordering and strong superstructures, manifested by a high crystallinity of the PC soft phase and a strong self-assembly of linear hard segments (HS). At the optimum composition, both supramolecular structures percolate resulting thus in the singnificant reinforcement. The PU, undergoing order–disorder transitions, involves three types of physical crosslinks with different thermal stability; PC crystalline phase, HS domains and in addition the entanglements. The structure evolution and reversible sol–gel transition during formation/breaking of the corresponding physical networks was followed by rheology, DSC and FTIR. The kinetics of build-up and stability of physical networks is governed by the content of HSs. The investigation contributed to the understanding and control of the thermal phase transitions of supramolecular structures in aliphatic PCPUs. The strong supramolecular structure undergoing order–disorder transitions, presence of thermally stable entanglement network and excellent mechanical properties make the PCPU suitable as a strong self-healing polymer. Two structural motifs are present: the thermally sensitive structure generating self-healing properties and the shape persistent entanglement network structure preventing the irreversible deformation. The efficient healing and restoration of the original structure and mechanical properties after damage of the polymer were checked by microscopy and tensile testing.

In the current work, we study the photoluminescence and anisotropic structure of PEDOT which is obtained in the presence of ions that perturb the water structure (ions in Hofmeister series). The water content in PEDOT has been confirmed by TGA and DSC measurements. The weight loss and heat flux together provided refined information about water content in the synthesized PEDOT, and based on the characteristic energy value, we conclude that the water molecules are bonded to the PEDOT chains by hydrogen bonds. The physicochemical properties of the such prepared PEDOT have been studied, e.g. the presence of photoluminescence is observed for PEDOT in the solid-state (thin film) with the longest Stokes shift (273 nm). Similarly, photoluminescence has been detected for the aqueous PEDOT suspension with the lifetime of the excited state in the range of nanoseconds. Moreover, the PEDOT chains can undergo rearrangements under electrochemical performance with the formation of an anisotropic structure, which is confirmed by polarized microscopy and XRD measurements. The photoluminescence spectrum of the anisotropic PEDOT film contains sharp, well-resolved peaks.

Performance of a proton exchange membrane fuel cell (PEMFC) is significantly determined by the structure and composition of the electrode layer. Electrode layers are formed from inks consisting of platinum-doped carbon black particles, perfluorosulfonic acid (PFSA) ionomer and a dispersing solvent. Interaction between these materials mainly influences suspension stability, ionomer conformation and therewith layer morphology. We characterize the interplay between a short sidechain (SSC) PFSA ionomer (Aquivion® D79-25BS) and a solvent mixture (diacetone alcohol (DAA) and water with different weight ratios) by using Hansen solubility/dispersibility parameters (HSP) and by experimental tests. It was found that HSPs are well suitable to describe the ionomer/solvent interactions. In particular, the HSP difference in terms of the hydrogen bonds is responsible for the poor affinity between ionomer and solvent at low DAA concentrations. With increasing DAA content the affinity between ionomer and solvent increases as indicated by better matching HSPs. For an ionomer concentration of 4 wt%, Aquivion always forms molecular solutions for all DAA-in-water mixing ratios. Self-organization of the ionomer molecules changes from densely packed/collapsed molecules with highly deprotonated sulfonic acid side groups at low DAA concentrations to unfolded Aquivion molecules with a low dissociation degree of the sulfonic acid groups at high DAA concentrations.

Polypyrrole/molybdenum disulfide (PPy/MoS2) composites were synthesized by in-situ chemical polymerization of pyrrole in the presence of MoS2 flakes. The conductivity of the composite with a moderate content of PPy (15–30 wt%) reached 13 S cm−1, which is markedly higher than the conductivity of both the pristine PPy and MoS2, 1 and 10−6 S cm−1, respectively. The improved conductivity was explained by the formation of ordered thin PPy films with high conductivity at the MoS2 surface. At higher pyrrole content, globular PPy was formed in the bulk of the composite resulting in an increase of a disordered polymer fraction, and the conductivity decreased. The composite conductivity is thus controlled not only by content of PPy but also by the proportions between ordered and disordered PPy phases. The structural and morphological characterization of composite materials is based on Fourier-transform infrared and Raman spectroscopies, wide-angle X-ray diffraction, and scanning and transmission electron microscopies. The charge-carrier transport in the composites fits the Mott variable-range hopping mechanism.

Addition of high-aspect-ratio (AR) nanofillers can markedly influence flow behavior of polymer systems. As a result, application of graphite nanoplatelets (GNP) allows preparation of microfibrillar composites (MFC) based on PCL matrix reinforced with in-situ generated PLA fibrils. This work deals, for the first time, with preparation of analogous melt-drawn fibers. Unlike other blend-based fibers, the spinning and melt drawing leads to structure of deformed inclusions due to unfavorable ratio of rheological parameters of components. Subsequent moderate cold drawing of the system with dissimilar deformability of components causes strengthening with PLA fibrils. Unexpectedly, high velocity and extent of cold drawing leads to structure with low-AR inclusions, similar to the original melt-drawn blend. Extensive fast deformation of the soft PCL matrix does not allow sufficient stress transfer to rigid PLA. In spite of peculiarities found, the GNP-aided melt spinning allows facile preparation of biodegradable biocompatible fibers with wide range of diameters (80–400 µm) and parameters (2.35–18 cN/tex).

The effect of nanofillers (NF) on parameters of polymer blends in microfibrillar composites (MFC) is complex due the effect of NF on melt drawing. This work concerns HDPE/PA66 modified with graphite nanoplatelets (GNP) prepared by different mixing protocols. GNP influence the dispersed phase size in the original blend negligibly and mostly lead to finer high-aspect ratio fibrils, i.e. GNP rather support elongation of inclusions than coalescence in the course of drawing. Favourable mechanical behaviour, exceeding predicted one, was found with low GNP content using the PA66 masterbatch. MFC with similar structure and GNP localization in PA66 show marked differences in properties depending on mixing protocol. Antagonistic effects found for the HDPE masterbatch indicate high effect of GNP migration between the components which affects the interphase by variation of crystallinity. The results confirm complex effect of GNP and dominancy of other GNP-induced effects over dual reinforcement with GNP and PA66 microfibrils.

The relations between crystalline structure and micromechanical properties of α-, β- and γ-phase of isotactic polypropylene (iPP) were investigated. The iPP samples with various crystalline phase compositions were prepared by a controlled high-pressure crystallization that enabled us to obtain not only α-iPP and β-iPP modifications, but also a series of almost pure γ-iPP samples with gradually changing morphology, crystallinity and lamellar thickness. The micromechanical properties were assessed by instrumented microindentation hardness testing (MHI), from which we determined indentation hardness (HIT), indentation modulus (EIT), indentation creep (CIT) and elastic part of the indentation work (ηIT). It was demonstrated that γ-iPP does not necessarily exhibit better mechanical performance than α- and β-iPP, as suggested by some previous studies, because the final properties are strongly influenced not only by the phase composition (i.e. by the content of α-, β- and γ-phase), but also by the overall crystallinity.

Modifications of GO by polymer chains may promote, in addition to exfoliation, also formation of ordered structures in epoxy. However, the contribution of self- assembly in the uncured matrix and reaction-induced phase separation to this process is not clear. SAXS study of analogous liquid and cured epoxy reveals that single grafted GO forms ordered structures only due to RIPS of grafted rubber. The marked self-assembly of bimodally grafted GO (BGO) before curing indicates that such modification changes its ordering performance substantially. Moreover, formation of ordered lamellar structures in liquid epoxy accompanied by easy migration of BGO may lead to formation of these arrays at the interface in carbon fibre composites. As a result, in-situ formation of effective nacre-like structures on the surface of CF, increasing delamination resistance, can be achieved.

In this study the behaviour and structure of a Nafion® 117 membrane exposed to liquid water at temperatures and pressures of up to 150 °C and 700 kPa, respectively, were investigated. The results clearly showed that, as the temperature of the environment approaches or exceeds the glass transition temperature of the membrane, it undergoes extensive swelling. This is connected with several changes in the membrane structure which have a predominantly detrimental influence on the functional properties of the membrane, such as ionic conductivity and ionic exchange capacity. The extent and rate of the changes increase with both rising temperature and pressure. While the changes at 150 °C and 700 kPa take place in the order of tens of minutes, at 110 °C and 500 kPa several hundreds of hours are required. The changes are enabled by amorphisation of pseudo-crystalline domains which are responsible for keeping the membrane structure intact. The changes in the internal structure were followed using small-angle X-ray scattering and visualised by current-sensing atomic force microscopy.

The modification of epoxy with polymer-grafted graphene oxide (GO) is a radical alternative to mere combination of GO with a polymeric modifier. Here, this aspect is revealed for the case of bimodal grafting of GO with hydrophobic polybutadiene and hydrophilic polyoxypropylene or polyethylene glycol utilizing grafting-to approach to link different chains in the plane and edge area of GO. The results indicate fair ability of bimodally grafted GO to form ordered lamellar structures in epoxy. However, these structures show larger distance between less aligned GO plates in contrast to tightly aligned GO arrangement in case of single grafting. This is enabled by repulsive interactions between dissimilar chains. Such a structure with higher mobility of grafted chains has favorable effect on mechanical performance of epoxy. The effect of chain type and geometry of grafting is highlighted as well. Important finding is promotion of lamellar structure formation also by grafted low-m. w. compounds.

Improvement of the mechanical properties of FFF 3D printed CF/PEEK composites was achieved by printing under favorable crystallization conditions. It was possible to improve the layer-layer tensile strength more than fivefold from 6.96 MPa to 36.28 MPa by printing in a specially customised, low cost printer operated with a heated print chamber at 230℃. The influence of the chamber temperature on the mechanical and crystalline structure was investigated to determine the best conditions. A maximum flexural modulus of 14 946 MPa and flexural stress at break of 248.9 MPa were achieved. A proof of concept study involved the 3DP of a CF/PEEK mould tooling insert for injection moulding. This insert replaced a costly traditional metal insert to print short production runs of ABS and HIPS polymers. This work offers a low cost and rapid means to produce effective tooling inserts for the injection moulding industry.

The process of ageing of polypyrrole is accompanied by gradual changes in its chemical composition, protonation level and charge transport mechanism. Although these changes are often limiting for practical application of polypyrrole, they are still far from being understood. In our contribution, natural ( i.e. ageing at room temperature) and accelerated ageing (at 120 °C) of polypyrrole nanotubes were studied. Natural ageing for about 3 year timespan lead to relative decrease of sample conductivity to about 0.2 of its initial σ 0 value. Accelerated ageing caused a dramatic decrease of 7 orders of magnitude after about 1000 h accompanied by partial deprotonation and backbone oxidation as confirmed by infrared, Raman and XPS spectroscopy and elemental analysis. Occurrence of crystalline domains was attributed to residual methyl orange and was not affected by ageing. The presence of methyl orange was found crucial for improving stability of sample conductivity; it caused about 4 orders of magnitude enhanced conductivity when compared with polypyrrole without methyl orange. In macroscopic scale the conductivity loss was found to be a spatially homogeneous process as revealed by electrical tomography. With increasing ageing time, besides gradual degradation on microstructural level, a qualitative change of charge transport mechanism was found.

Modification of polymer blends with nanofillers is an efficient way to improve material parameters. This work deals with application of neat and stearylamine-modified graphene oxide in the polyamid...

This paper reports the synthesis, characterization, and electrochemical performance of nickel-cobalt hydroxide nanosheets. The hydroxide nanosheets of approximately 0.7 nm thickness were prepared by delamination of layered nickel-cobalt hydroxide lactate in water and formed transparent colloids that were stable for months. The nanosheets were deposited on highly oriented pyrolytic graphite by spin coating, and their electrochemical behavior was investigated by cyclic voltammetry in potassium hydroxide electrolyte. Our method of electrode preparation allows for studying the electrochemistry of nanosheets where the majority of the active centers can participate in the charge transfer reaction. The observed electrochemical response was ascribed to mutual compensation of the cobalt and nickel response via electron sharing between these metals in the hydroxide nanosheets, a process that differentiates the behavior of nickel-cobalt hydroxide nanosheets from single nickel hydroxide or cobalt hydroxide nanosheets or their physical mixture. The presence of cobalt in the nickel-cobalt hydroxide nanosheets apparently decreases the time of electrochemical activation of the nanosheet layer, which for the nickel hydroxide nanosheets alone requires more potential sweeps.

The impact of pre-set extension on the degree of hydrolytic degradation in all-aliphatic polyurethane (PU) films was tested in phosphate-buffered saline (PBS) for a period of up to 12 months. The PUs were synthesized from polycarbonate-based macrodiol (MD), diisocyanate-1,6-hexane (HDI), butane-1,4-diol (BD) and d,l-lactide-based oligomeric diol (DLL). Macrodiol with molecular weights of ∼2800 Da, three DLL oligomers (∼400, 660 and 850 Da) and three MD-to-BD-to-DLL molar ratios were chosen for PU synthesis. The isocyanate-to-total-hydroxyl-group ratio was kept constant at 1.05. The functional properties of raw polyurethane films and the samples immersed for 1, 3, 6, 9 and 12 months in a model physiological environment (37 °C, pH = 7.4) were studied. The pre-set extension varied from 20 up to 150% and was applied on PUs with or without any DLL. The given pre-set strain had only slight – but varying – influence on the extent of the hydrolytic process, compared to the non-extended analogues. In samples that underwent efficient orientation and crystallization under strain (three-component PU and PU containing DLL ca. 400 Da), the degradation process was slightly inhibited compared with that of the unstrained analogues. If the systems were composed of sequences not capable of efficient crystallization under strain (PUs containing DLL ca. 660 and 850 Da), then the hydrolytic degradation of the pre-strained samples was accelerated. The observed changes in the functional properties of the mechanically strained PU materials subjected to the long-term hydrolytic process under physiology-mimicking conditions are important for potential medical, package coating, and film applications.

This work describes the solvent-free sol–gel synthesis of epoxy-functionalized silica-based precursors in the presence of 1-butyl-3-methylimidazolium-based ionic liquids (ILs) containing different anions: chloride (Cl–) and methanesulfonate (MeSO3–). The IL-driven sol–gel mechanisms were investigated in detail using experimental characterizations (29Si NMR and ATR FTIR spectroscopy) and a theoretical computational method based on density functional theory (DFT). We observed complex IL influence on both hydrolysis and condensation steps, involving especially H-bonding and Coulomb coupling stabilization of the process intermediates. The obtained IL–silica precursors and their further xerogels were widely characterized (rheology measurements, MALDI TOF, 29Si NMR, ATR FTIR, and DFT simulation), which allowed observation of their precise silica structures and established their most energetically favorable conformations. The detected silica structures were dependent on the IL type and varied from highly condens...

The hydrolytic degradation of aliphatic polyurethane (PU) films made from polycarbonate-based macrodiol (MD), diisocyanate-1,6-hexane, butane-1,4-diol (BD) and d , l -lactide-based oligomeric diol (DLL) was studied. The influence of the length of DLL was tested in phosphate-buffered saline (PBS) for periods of up to 12 months. One macrodiol (molecular weight ∼2000 Da), three DLL oligomers (∼400, 660 and 850 Da) and three MD-to-BD-to-DLL molar ratios were chosen for the PU synthesis. The isocyanate-to-total hydroxyl-group ratio was kept constant at 1.05. The functional properties of raw polyurethane films and samples immersed for 1, 3, 6, 9 and 12 months in a model physiological environment (37 °C, pH = 7.4) were studied from the segmental to the macroscopic level. Tensile testing and water uptake experiments, as well as differential scanning calorimetry (DSC), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FTIR) and wide-angle X-ray diffraction (XRD) analyses, were used for the characterization of the raw and PBS-treated films. The study shows that the length of the DLL chain is much more important for functional PU properties than the mass content of DLL in the PU film. The incorporation of the shortest DLL into the PU backbone leads to a degradable PU material with outstanding tensile properties when not subjected to the hydrolytic treatment. However, the incorporation of oligomers with longer DLL chains results in PU materials with substantially deteriorated tensile characteristics due to more pronounced phase separation compared to systems without DLL or with the shortest DLL. The degradability of the PU films can be controlled to a relatively broad extent by altering DLL content and length. The investigation of functional properties of new PU materials during the hydrolytic process under physiology-mimicking conditions is important for potential medical/package coating/film applications.

Biodegradable thermoplastic starch (TPS) composites with isometric titanium dioxide nanoparticles (TiO2; diameter ~100 nm) and elongated titanate nanotubes (TiNT; diameter ~20 nm and aspect ratio >50) were prepared from wheat and tapioca starch. The preparation was based on our recently developed two-step procedure consisting of the solution casting (SC) followed by the melt mixing (MM), which had been shown to yield highly homogeneous TPS in our previous study. In this work we demonstrated that the type of the TPS matrix and the type of the filler had significant impact on the morphology and the properties of the final composites. Multiple microscopic techniques (LM, SEM, and TEM) evidenced that the TPS/TiO2 composites exhibited a very homogeneous dispersion of the filler, while the TPS/TiNT composites contained micrometer-size agglomerates of TiNT. Moreover, all composites with the wheat starch matrix [TPS(w)] showed a higher filler agglomeration than the corresponding composites with the tapioca starch matrix [TPS(t)]. Rheological experiments showed that the TiO2 and TiNT fillers had quite small impact on the viscosity of the TPS(w) matrix, probably due to slightly higher agglomeration, poorer dispersion, and weaker matrix-particle interactions. On the other hand, the TPS(t) matrix was influenced by both fillers significantly: the TiO2 nanoparticles with almost ideal dispersion formed a physical network in the TPS(t) matrix, which significantly increased the viscosity of the composite, whereas the TiNT nanotubes seemed to destruct the TPS(t) matrix partially, resulting in decreased viscosity of the composite. DMTA results confirmed the rheological measurements: Storage moduli (G') showed that TPS(t) and its composites with TiO2 were stiffer than the corresponding TPS(w) samples, while the TPS(t)/TiNT composites were less stiff than TPS(w)/TiNT. Also loss moduli (G“) confirmed the difference between tapioca starch and wheat starch composites, which differed by their glass transition temperatures [Tg of TPS(w) < Tg of TPS(t)]. The rheological and DMTA results were supplemented and supported by IR, XRD, and TGA measurements.

The phyto-development of nanomaterials is one of the main challenges for scientists today, as it offers unusual properties and multifunctionality. The originality of our paper lies in the study of new materials based on biomimicking lipid bilayers loaded with chlorophyll, chitosan, and turmeric-generated nano-silver/silver chloride particles. These materials showed a good free radical scavenging capacity between 76.25 and 93.26% (in vitro tested through chemiluminescence method) and a good antimicrobial activity against Enterococcus faecalis bacterium (IZ &gt, 10 mm). The anticancer activity of our developed bio-based materials was investigated against two cancer cell lines (human colorectal adenocarcinoma cells HT-29, and human liver carcinoma cells HepG2) and compared to one healthy cell line (human fibroblast BJ cell line). Cell viability was evaluated for all prepared materials after a 24 h treatment and was used to select the biohybrid with the highest therapeutic index (TI), additionally, the hemolytic activity of the samples was also evaluated. Finally, we investigated the morphological changes induced by the developed materials against the cell lines studied. Biophysical studies on these materials were done by correlating UV–Vis and FTIR absorption spectroscopy, with XRD, SANS, and SAXS methods, and with information provided by microscopic techniques (AFM, SEM/EDS). In conclusion, these “green” developed hybrid systems are an important alternative in cancer treatment, and against health problems associated with drug-resistant infections.

Polymers 13(9), 1465 (1-14) (2021). doi:10.3390/polym13091465, Here, we report on the construction of biodegradable poly(ethylene oxide monomethyl ether) (MPEO)-b-poly(��-caprolactone) (PCL) nanoparticles (NPs) having acid-labile (acyclic ketal group) linkage at the block junction. In the presence of acidic pH, the nanoassemblies were destabilized as a consequence of cleaving this linkage. The amphiphilic MPEO-b-PCL diblock copolymer self-assembled in PBS solution into regular spherical NPs. The structure of self-assemble and disassemble NPs were characterized in detail by dynamic (DLS), static (SLS) light scattering, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM). The key of the obtained NPs is using them in a paclitaxel (PTX) delivery system and study their in vitro cytostatic activity in a cancer cell model. The acid-labile ketal linker enabled the disassembly of the NPs in a buffer simulating an acidic environment in endosomal (pH ~5.0 to ~6.0) and lysosomal (pH ~4.0 to ~5.0) cell compartments resulting in the release of paclitaxel (PTX) and formation of neutral degradation products. The in vitro cytotoxicity studies showed that the activity of the drug-loaded NPs was increased compared to the free PTX. The ability of the NPs to release the drug at the endosomal pH with concomitant high cytotoxicity makes them suitable candidates as a drug delivery system for cancer therapy., Published by MDPI, Basel

Diseases related to a disrupted skin barrier are accompanied by lower levels of ceramides in the stratum corneum (SC) lipid matrix. Delivering ceramides directly into damaged skin is a viable alternative to conventional corticosteroids, but is hindered by their low skin bioavailability and limited nanoformulation ability. Here, we developed stable liposomal systems containing ceramides and other SC lipids, and tested their effectiveness in skin barrier repair. Lipid film hydration and high-pressure homogenization were used to prepare different types of liposomes. To determine the stability, the particle size and polydispersity index were measured. The optimal systems were found to include ceramide 3 and 6, cholesterol and stearic acid, with 10% urea in phosphate-buffered saline as the aqueous phase. The ability of the system to repair chemically-damaged porcine skin was tested. While treatment by a standard lipid suspension reduced the passage of a model permeant only to a limited extent, drug flux through the liposomally-treated skin was much closer to permeation through intact skin. The non-homogenized liposomes were more effective than their homogenized version. These findings were also confirmed by FTIR measurements. This suggests that our approach to liposomal development has considerable potential for the repair of a disrupted skin barrier.

Carbon nanospecies (CNPs) are of high interest in current research due to their many unique properties. They may be created by common processes, such as burning. Therefore, they can become potential contaminants and may have a negative impact on human health and the biosphere. Moreover, they may also catalyze protein misfolding and subsequent amyloid formation, which is extremely hard to treat. We investigated the influence of single-walled carbon nanotubes (SWNTs), fullerene (C60), carbon quantum dots (CDs) and nanodiamonds (NDs) on amyloid formation. This research utilized the hen egg-white lysozyme (HEWL) as a model system. Fibrils were detected by fluorescence of thioflavin-T (ThT) or Nile red (NR) and the results were confirmed by transmission electron microscopy (TEM). We have found that NDs promoted amyloid fibril formation at all concentrations. The highest concentration of C60 (250 μg ml−1) accelerated the process of fibrillation, while smaller concentrations (16 and 80 μg ml−1) prolonged the lag phase and were comparable to the control. SWNTs prolonged the lag phase of amyloid formation at all concentrations. CDs efficiently terminated the growth of amyloid fibrils. When we compared the amyloidogenicity of all four types of CNPs, the following trend was apparent: NDs > control > C60 > CDs > SWNTs.