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The paper deals with the development of an antinucleating strategy to prevent the crystallization of Artemisinin (ART), a potent natural antimalarial agent, through its encapsulation into core–shell nanofibers, constituted by a core of ART blended with a hyperbranched poly(butylene adipate) (HB), covered with a shell of poly(vinyl pyrrolidone) (PVP). The highly branched polymer acted as an effective antinucleating agent. Scanning and transmission electron microscopy analyses evidenced the regular and homogenous morphology of the core–shell electrospun nanofibers. Attenuated total reflectance spectroscopy, differential scanning calorimetry and X-ray diffraction analysis were utilized to assess the activity and the physical state of ART into the nanofibers. It was demonstrated that ART was successfully encapsulated in electrospun nanofibers and could efficiently retain its amorphous state.

Composites based on poly(butylene succinate-co-butylene adipate) (PBSA) containing amorphized and crystalline cellulose reinforcements have been prepared and characterized. In order to improve the polymer/filler interfacial adhesion, an efficient compatibilizing agent has been synthesized by chemical modification of PBSA and characterized by FT-IR, FT-NIR and 1H NMR spectroscopy. Uncompatibilized and compatibilized composites have been tested through morphological, mechanical, calorimetric and thermogravimetric analysis. Moreover, water vapor permeability and biodegradation kinetics of composites have been investigated. The addition to PBSA of cellulose fillers differing from each other by crystallinity degree and morphology, and the use of a compatibilizing agent have allowed modulating tensile and thermal properties, water vapor transmission rate and biodegradation kinetic of the composites.

Light‐triggered release of active ingredients from polymeric nanosized capsules can be employed in a wide range of applications, such as biomedicine, active packaging, and cosmetics. However, the preparation of core‐shell polymeric nanocarriers typically involves the use of toxic organic solvents. To improve the sustainability and safety of nanocapsule applications, we demonstrate that natural essential oils can be used both as a solvent and as an active material in light‐responsive nanocapsules synthesized via miniemulsion polycondensation. The documented antimicrobial, anti‐inflammatory, and antioxidant activity of essential oils enables the design of multipurpose light‐responsive delivery platforms. The photo‐responsive behavior of the capsules, achieved by means of photochromic azobenzene segments embedded in the capsule shell, is triggered by UV light irradiation (λmax = 360 nm). Light‐induced release kinetics of the essential oils and a fluorescent probe molecule, coumarin‐6, are evaluated via UV‐vis spectroscopy and spectrofluorimetry, respectively, demonstrating the efficiency and reliability of the release mechanism. Biological tests prove that the capsules are non‐cytotoxic and readily internalized by cells, indicating the suitability of these smart nanocarriers for biological applications

This work reports on the preparation of UV-light responsive nanocapsules based on cross-linked polyamide, obtained by miniemulsion interfacial polymerization. The photo-triggered E-Z transition of azobenzene moieties of the polymer backbone enabled controlled release of encapsulated molecules. Appropriate selection of emulsion conditions allowed tailoring size distribution of the resulting nanocapsules. The light responsiveness of the nanocapsule systems has been evaluated by monitoring size change and release of a fluorescent probe upon UV irradiation, and an unambiguous relationship between capsule size and release kinetics has been highlighted. In particular, the smaller the capsule size, the faster the achieved release. Therefore, the photoresponsiveness of the nanosized capsule systems can be modulated by a proper selection of emulsion and processing parameters. The significance of the reported results lies in the size control of the encapsulating particles, which in turn enables to tailor their swelling kinetics, and to precisely design light-controlled release systems. (C) 2015 Elsevier Ltd. All rights reserved.

DOI: 10.3390/polym9010008 URL: http://www.mdpi.com/2073-4360/9/1/8 Filiació URV: SI Inclòs a la memòria: SI A significant amount of academic and industrial research efforts are devoted to the encapsulation of active substances within micro- or nanocarriers. The ultimate goal of core-shell systems is the protection of the encapsulated substance from the environment, and its controlled and targeted release. This can be accomplished by employing "stimuli-responsive" materials as constituents of the capsule shell. Among a wide range of factors that induce the release of the core material, we focus herein on the light stimulus. In polymers, this feature can be achieved introducing a photo-sensitive segment, whose activation leads to either rupture or modification of the diffusive properties of the capsule shell, allowing the delivery of the encapsulated material. Micro- and nano-encapsulation techniques are constantly spreading towards wider application fields, and many different active molecules have been encapsulated, such as additives for food-packaging, pesticides, dyes, pharmaceutics, fragrances and flavors or cosmetics. Herein, a review on the latest and most challenging polymer-based micro- and nano-sized hollow carriers exhibiting a light-responsive release behavior is presented. A special focus is put on systems activated by wavelengths less harmful for living organisms (mainly in the ultraviolet, visible and infrared range), as well as on different preparation techniques, namely liposomes, self-assembly, layer-by-layer, and interfacial polymerization.

The removal of dye and toxic ionic pollutants from water is an extremely important issue that requires systematic and efficient adsorbent preparation strategies. To address this challenge, we developed composite chitosan (CS)-based hydrogels containing hyper-crosslinked polymer (HCP) particles to be used as broad-spectrum adsorbents. The goal is to efficiently combine the dye adsorption ability of chitosan and the capacity of the porous particles of trapping pollutant molecules. The HCP particles are well distributed and firmly embedded into the chitosan matrix and the composite hydrogels exhibit improved mechanical properties. Adsorption experiments reveal a synergistic effect between CS and HCP particles, and the samples are able to remove both anionic and cationic dyes (indigo carmine, rhodamine 6G and sunset yellow) from water. The maximum dye uptake is higher than that of comparable biosorbents. Moreover, the mechanical properties of the composite hydrogels are enhanced respect to pure CS, and the samples can be regenerated and reused keeping their adsorption ability unaltered over successive cycles of adsorption, desorption, and washing.

Organic–inorganic perovskites are semiconductors used for applications in optoelectronics and photovoltaics. Micron and submicron perovskite patterns have been explored in semitransparent photovoltaic and lasing applications. In this work, we show that a polymeric medium can be used to create a patterned perovskite, by using a novel and inexpensive approach.

Carbon nanoparticles are becoming ubiquitous in many fields of science and technology. However, a grand challenge remains in assembling, patterning, and positioning or even simple manipulation of CNTs for complex functional assemblies. CNTs have in fact enormous perspectives for application in biotechnologies as bactericide agents or as prominent tools for investigating cell mechanisms, or more in general as functionalized nanoparticle-vectors, but their exploitation requires viable technology at the lab-on-a-chip scale. Many approaches have been attempted in developing technologies for manipulating CNTs. One elective approach is based on electric fields driven mechanisms such as DEP forces. A variety of chips have been designed and realized with this aim. Here we report on a novel hybrid microfluidic chip made by assembling a polar-dielectric crystal with polymeric microfluidic channels. One challenging feature of such a hybrid device approach, based on an electrode-free dielectrophoretic (DEP) approach, is that it makes use of surface charge templates for self-assembling and manipulation of CNTs in liquid media directly into a microfluidic channel. Here various examples of self-assembly in microfluidic channels as well as separation and collection of two classes of nano/microparticles are reported. The method can open the way to novel fabrication protocols for the realisation of future flexible devices with new and more complex functionalities, highly desirable in electronics as well as in biotechnology at the lab-on-a-chip scale. 2014 The Royal Society of Chemistry.

Poly(3-hydroxybutyrate) (PHB) is a biodegradable polymer, whose applicability is limited by its brittleness and narrow processing window. In this study a pomace extract (EP), from the bio-waste of winery industry, was used as thermal and processing stabilizer for PHB, aimed to engineer a totally bio-based system. The results showed that EP enhanced the thermal stability of PHB, which maintained high molecular weights after processing. This evidence was in agreement with the slower decrease in viscosity over time observed by rheological tests. EP also affected the melt crystallization kinetics and the overall crystallinity extent. Finally, dynamic mechanical and tensile tests showed that EP slightly improved the polymer ductility. The results are intriguing, in view of the development of sustainable alternatives to synthetic polymer additives, thus increasing the applicability of bio-based materials. Moreover, the reported results demonstrated the feasibility of the conversion of an agro-food by-product into a bio-resource in an environmentally friendly and cost-effective way. © 2012 Elsevier B.V.

The role of additives in commodity and specialty polymeric artifacts is of key importance since pure polymers often show poor resistance to external factors (such as weathering, mechanical stress, etc.) during their processing or end-use application. This chapter provides a technical overview of the most important classes of polymer additives that can ensure protection against weathering agents (UV radiation, oxygen), resistance to heat or flames, and improvement of physical and mechanical properties, particularly plasticization and impact resistance. Compatibilization of polymer blends is also discussed due to its importance in recycling of plastic materials. Since esthetic appearance of finished products is of great concern, different coloring technologies are also reported herein, ranging from standard to “special effect” formulations. In the final section a remark on bio-based additives is provided, to account for the social and technological push toward biopolymers and all bio-based formulations. For a complete insight on this topic, for each class of polymer additives a wide range of commercially available products is provided together with their supplier names and main applications in polymer formulations.

Treatment with boiling 6 M HCl increases up to 30 times the intrinsic antioxidant potency of spent coffee grounds, leading to a versatile multifunctional material (hydrolyzed spent coffee grounds, HSCG). Spectral and morphological analyses suggest that the remarkable potentiation of the antioxidant activity is due to efficient removal of the hydrolyzable components, mainly carbohydrates, making the polyphenol-rich component available for interaction with free radicals and oxidizing species. HSCG efficiently protects hepatocarcinoma (HepG2) cells from oxidative stress-induced injury and delays lipid peroxidation in fish and soybean oils. Moreover, films made of polyethylene/2% HSCG blends display greater stability to thermal and photo-oxidative degradation. HSCG may thus represent an easily accessible and sustainable alternative to currently available biomaterials with intrinsic antioxidant properties for biomedical, industrial, and technological applications., This work was partially supported by grants from Italian MIUR (PRIN 2010-2011 PROxi project).

The determinants of the broadband absorption spectrum of eumelanins are still largely unknown. Herein we report a novel approach to investigate eumelanin chromophore which is based on the biomimetic oxidation of the key monomer precursor, 5,6-dihydroxyindole (DHI, 1), with peroxidase/hydrogen peroxide in phosphate buffer, pH 7, containing 1-5% polyvinylalcohol (PVA, 27 000 Da). This approach relies on the discovery that as low as 1% PVA can prevent precipitation of the growing melanin polymer thus allowing investigation of the chromophoric phases accompanying oxidation of DHI without confounding scattering effects. Spectrophotometric monitoring showed the initial development of a band around 530 nm persisting for about 1 h before gradually changing into the typical broadband spectrum of eumelanin. Reductive treatment caused a significant absorbance decrease in the visible region without affecting an absorption band around 320 nm. Initial product analysis indicated an altered formation ratio of 2,4'-biindolyl (2) and 2,7'-biindolyl (3) relative to control experiments. Overall, these results demonstrate for the first time that the development in solution of visible chromophores since the early oligomer stages is independent of strong aggregation/precipitation phenomena.

Hyper-crosslinked (HCL) polystyrenes show outstanding properties, such as high specific surface area and adsorption capability. Several researches have been recently focused on tailoring their performance for specific applications, such as gas adsorption and separation, energy storage, air and water purification processes, and catalysis. In this review, main strategies for the realization of HCL polystyrene-based materials with advanced properties are reported, including a summary of the synthetic routes that are adopted for their realization and the chemical modification approaches that are used to impart them specific functionalities. Moreover, the most up to date results on the synthesis of HCL polystyrene-based nanocomposites that are realized by embedding these high surface area polymers with metal, metal oxide, and carbon-based nanofillers are discussed in detail, underlining the high potential applicability of these systems in different fields.

A previously synthesized hyperbranched poly(butylene adipate) (HPBA) polymer was compared with a commercial dendritic polyol (HPOH) as a toughening agent for a commercial one-part epoxy resin. Both modifiers were added in weight percentages of 1, 3, 5, and 10%. The modified epoxies were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), melt rheological tests, and linear elastic fracture mechanics. Blend morphology and matrix–modifier interactions were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The toughness-improvement effect was achieved without substantial impairment of thermomechanical properties or degradation of the thermal stability of the epoxy resin. A meaningful decrease in viscosity was achieved with both modifiers, contributing to an easier infusion processability. No evidence of new chemical linking was found although phase separation was observed by SEM, leading to the conclusion that only interfacial linkage occurs between modifiers and epoxy chains. SEM analysis also clearly shows the fracture mode changing from brittle to ductile by addition of modifiers, which was more evident for blends of HPBA.

The synthesis, structural characterization and properties of a new bioinspired phenolic polymer (polyCAME) produced by oxidative polymerization of caffeic acid methyl ester (CAME) with horseradish peroxidase (HRP)-H2O2 is reported as a new sustainable stabilizer toward polyethylene (PE) thermal and photo-oxidative degradation. PolyCAME exhibits high stability toward decarboxylation and oxidative degradation during the thermal processes associated with PE film preparation. Characterization of PE films by thermal methods, photo-oxidative treatments combined with chemiluminescence, and FTIR spectroscopy and mechanical tests indicate a significant effect of polyCAME on PE durability. Data from antioxidant capacity tests suggest that the protective effects of polyCAME are due to the potent scavenging activity on aggressive OH radicals, the efficient H-atom donor properties inducing free radical quenching, and the ferric ion reducing ability. PolyCAME is thus proposed as a novel easily accessible, eco-friendly, and biocompatible biomaterial for a sustainable approach to the stabilization of PE films in packaging and other applications.

The combined effect of melt annealing and surface modification of multiwalled carbon nanotubes (MWCNT) on polypropylene (PP) based nanocomposites is reported. Melt annealing markedly improved the filler dispersion in PP. The rheological and electrical percolative threshold was achieved at a content of 3 wt% MWCNT, due to the dynamic reconstruction of nanotube network in the polymer matrix. This behaviour was particularly evident in the case of surface-modified MWCNT. However, the heat treatment also induced an overall worsening of mechanical properties due to polymer heterogeneous oxidation at a microscopic scale, as detected by oxygen mapping through SEM/EDS. Crack initiation sites eventually leading to the failure of the polymer were formed due to peroxide-mediated spreading of oxidation, radiating from residual polymerisation catalyst particles. FTIR-ATR spectroscopy demonstrated that blooming of the phenol stabilizer due to thermal annealing was responsible for early oxidation of polypropylene. The reported results highlight the advantages and drawbacks of physical strategies designed to improve the dispersion stability of nanotubes in polymer nanocomposites.

Pristine and surface functionalized multiwalled carbon nanotubes (MWCNT) were melt mixed with a polypropylene (PP) polymer matrix. Rheology, morphology, electrical conductivity and mechanical properties of the nanocomposites were evaluated for different MWCNT loadings. Melt annealing effect on properties was also investigated. It was found that both surface functionalization of MWCNT and thermal annealing were able to favor a better dispersion of the particles, inducing the formation of a percolative network. © 2014 AIP Publishing LLC.

Stable chains of carbon-based nanoparticles were formed directly in polymer matrixes through an electrode-free approach. Spontaneous surface charges were generated pyroelectrically onto functionalized ferroelectric crystals, enabling the formation of electric field gradients that triggered the dipole-dipole interactions responsible for the alignment of the particles, while embedded in the polymer solution. The phenomenon is similar to the dielectrophoretic alignment of carbon nanotubes reported in the literature. However, here the electric fields are generated spontaneously by a simple heat treatment that, simultaneously, aligns the particles and provides the energy necessary for curing the host polymer. The result is a polymer sheet reinforced with well-aligned chains of carbon-based particles, avoiding the invasive implementation of appropriate electrodes and circuits. Because polymers with anisotropic features are of great interest for enhancing the thermal and/or the electrical conductivity, the electrode-free nature of this technique would improve the scaling down and the versatility of those interconnections that find applications in many fields, such as electronics, sensors, and biomedicine. Theoretical simulations of the interactions between the particles and the charge templates were implemented and appear in good agreement with the experimental results. The chain formation was characterized by controlling different parameters, including surface charge configuration, particle concentration, and polymer viscosity, thus demonstrating the reliability of the technique. Moreover, micro-Raman spectroscopy and scanning electron microscopy were used for a thorough inspection of the assembled chains. 2013 American Chemical Society.

The key structural factors underlying the unique black chromophore of eumelanin biopolymers have so far defied elucidation. Capitalizing on the ability of 1% polyvinylalcohol (PVA) to prevent pigment precipitation during melanogenesis in vitro, we have investigated the visible chromophore properties of soluble eumelanin-like polymers produced by biomimetic oxidation of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) in 1% PVA-containing buffer at pH 7. Upon dilution DHI-eumelanin solutions exhibited almost linear visible absorbance changes, whereas DHICA-eumelanin displayed a remarkable deviation from linearity in simple buffer, but not in PVA-containing buffer. It is suggested that in DHICA polymers, exhibiting repeated interruptions of interring conjugation due to lack of planar conformations, the black chromophore is not due to an overlap of static entities defined intrinsically by the conjugation length across the carbon frame, but results largely from aggregation-related intermolecular perturbations of the π-electron systems which are extrinsic in character.

A polyphenol-containing extract from winery bio-waste (EP) has been used as an additive for a starch-based polymer (Mater-Bi). EP was used to tailor Mater-Bi properties, thus avoiding the use of synthetic polymer additives. It was found that EP was able to efficiently modulate the processing, mechanical, thermal and biodegradation properties. The observed decrease in melt viscosity showed that EP could improve productivity in polymer processing. Owing to the plasticizing activity of the additive, larger values of elongation at break were found. Moreover, the Mater-Bi crosslinking, which occurs upon thermal aging, was delayed in the presence of EP. Finally, the bio-disintegration rate of doped Mater-Bi decreased, thus suggesting that EP acted as an antimicrobial agent by interfering with the bio-digestion of the polymer films.

In this work, a polyphenol-containing extract from winery bio-waste (EP) has been used as additive to tailor Mater-Bi properties. EP was able to efficiently modulate both polymer processing and mechanical, thermal and biodegradation properties. EP decreased the melt viscosity, behaved as a Mater-Bi plasticizer and delayed the Mater-Bi crosslinking process occurring upon thermal aging. Finally, the biodisintegration rate of doped Mater-Bi decreased, thus indicating that EP interfered with the microbial digestion of the polymer films.

Physical properties of epoxy resins filledwith microparticles are presented and discussed. Micropar-ticles were synthesized in the form of micron-sized,crosslinked spherical particles, with an excess of reactiveamino groups on their outer surface, and subsequentlyblended with EPON828-3,3 DDS in different weight per-cents(10and20wt%).Differentialscanningcalorimetryandscanning electronic microscopy were applied to investigatemicrosphere properties such as morphology, shape, size,and size distribution. Electron spectroscopy for chemicalanalysis was applied on particles to relate surface composi-tion and reactivity of microspheres. Rheological, dynamic–mechanical, and mechanical properties of the cured blendswere analyzed and related to the pure resin and to the sameresin modified with PES180. © 2004 Wiley Periodicals, Inc.J Appl Polym Sci 93: 2031–2044, 2004 Key words: adhesion; crosslinking; curing of polymers; res-ins; thermosets INTRODUCTION It is well known that physical properties of thermosetscan be improved by inclusion of a filler, as a secondphase, to the resin batch. For example, toughness isnoticeably increased by mixing reactive rubbers withepoxy resins. The same effect can be reached with theaddition of some reactive thermoplastics.In many cases, the target is viscosity modificationduring processing of thermosets. For this purpose, asuspension of solid particles, as well as of some ther-moplastics, included in the resin can be very useful inbalancing the proper viscosity profile during process-ing.In this article, a novel approach to change the vis-cosity of epoxy resins is presented. The method isbased on the inclusion of reactive microspheres pre-viously prepared by reaction of the epoxy monomerwith the curing agent.Over the last several years, a growing interest in theproduction of polymer particles was recorded.