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In the present work, hybrid organic-inorganic nanocomposite films based on poly(vinyl alcohol) (PVA) and CdSe quantum dots synthesized in aqueous medium were prepared without the use of organic solvents, by casting aqueous solutions of both PVA and nanoparticles. The effect of different capping agents employed during quantum dot synthesis on thermal, optical, and dielectric properties of nanocomposites was analyzed, finding that capping agents not only affect the interactions between nanoparticles and polymeric matrix, but also the size and photoluminescence of quantum dots, among other properties. Optical, thermal, dielectric and morphological characterization of nanocomposites has been carried out in terms of UV–vis spectroscopy, spectrofluorometry, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dielectric relaxation spectroscopy (DRS) and atomic force microscopy, respectively, finding that by the use of different capping agents, final properties of nanocomposites can be tuned, as interactions between PVA and CdSe quantum dots determine their final properties.

Transparent and flexible bionanocomposites with photochromic properties based on cellulose triacetate (CTA) and sol-gel synthesized V2O5 nanoparticles were prepared. Poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer was added to achieve nanostructured materials and simultaneously control the dispersion of synthesized V2O5 nanoparticles. Investigated bionanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), atomic force microscopy (AFM), tensile tests, and UV–vis spectroscopy. FTIR results confirmed the presence of hydrogen bonds in the bionanocomposites. The miscibility between components improved with the increase of sol-gel content resulting in a decrease of the Tg and Tm of CTA phase as indicated by DSC results. Addition of EPE triblock copolymer enhanced the photochromic properties of bionanocomposites reducing the time of recovery to the initial state after 5 min of UV light irradiation. The biocompatibility of pure CTA and EPE/CTA blends as well as the photochromic properties provided by synthesized V2O5 nanoparticles make their transparent and flexible bionanocomposites ideal for possible future applications.

Silica multi-layer stacks have been designed with the aim to provide broadband antireflective (AR) properties for glass components in concentrated photovoltaic (CPV) application. Silica porous coatings were grown by combining acid-catalyzed sol-gel route and evaporation induced self-assembly (EISA) method with four types of organic/inorganic systems. Sols were prepared using tetraethylorthosilicate (TEOS) as inorganic precursor assembled with two di-block copolymers, one tri-block copolymer and one cationic surfactant as organic templates. Optical properties were characterized by ellipsometry and spectrophotometry while the material structure was analyzed by environmental ellipsometric porosimetry (EEP) and atomic force microscopy (AFM). The concentration of inorganic and organic phases was optimized and a broadband AR bi-layer stack was obtained providing a 7.2% (under the reference AM1.5 solar spectral irradiance) increase in transmittance over bare glass in the wavelength range 300–2000 nm when coated on both sides. This work was supported by the Basque Government for EMAITEK 2017 program as well as the ELKARTEK projects FRONTIERS-2 (Contract no. KK2016-00093 ) and FRONTIERS-3 (Contract no. KK2017-00096 ) This work has received funding from the European Union's Horizon 2020 Research and Innovation Programme within the project CPVMatch under Grant agreement no. 640873 . The authors are solely responsible for the content of this work and it only reflects the author's view. The authors thank ICV-CSIC, Yolanda Castro and Alicia Durán for ellipsometry and EEP measurements.

The structure, morphology and final properties of synthesized waterborne poly(urethane-urea)s (WPUU) based on triblock copolymers containing hydrophilic poly(ethylene oxide) PEO block as polyol has been studied. Different molecular weight poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO) and poly(propylene oxide-b-ethylene oxide-b-propylene oxide) (PPO-b-PEO-b-PPO) triblock copolymers were used as polyols acting as soft segment. A Volatile Organic Compounds (VOCs) free synthesis procedure was followed to synthesize WPUU dispersions. Particle size, solid content and viscosity of the WPUU dispersions were measured. Atomic force microscopy was used to study the morphology, whereas size exclusion chromatography helped determining molecular weight of the WPUU films, prepared by solvent casting. Chemical structure was determined by FTIR and 1H NMR. Moreover, transmittance and thermal and mechanical properties of the WPUU films were also investigated. The use of PEO-b-PPO-b-PEO triblock copolymer led to dispersions with higher molecular weights and viscosities. WPUU films based on this triblock copolymer showed better mechanical properties, nevertheless they exhibited a lower transparency. All triblock copolymer based WPUU films led to nanostructured materials, which can act as template for dispersion of different kind of fillers extending possible application of waterborne polyurethanes. This work spotlights the possibility to synthesize waterborne poly(urethane-urea) dispersions with tailored properties using triblock copolymers as polyols.

Made available in DSpace on 2018-12-11T17:37:29Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-10-15 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Komagataeibacter rhaeticus, a bacterium isolated from Kombucha tea, was used to produce bacterial cellulose (BC) through its cultivation in a static sugarcane molasses (SCM) supplemented-culture medium (totally or partially), as an alternative carbon source. BC membranes were characterized by different physicochemical analysis using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), field emission gun-scanning electron microscopy (FEG-SEM), thermogravimetry analysis (TGA) and PeakForce quantitative nanomechanics atomic force microscopy (PeakForce (QNM-AFM)). FTIR, XRD and TGA results suggest great similarity among all membranes produced by distinct culture media. Although the glucose (F1) and SCM (F6) media presented the lowest BC yield, all SCM-supplemented culture media (from F2 to F5) showed BC yield values similar to the HS culture medium (F0). FEG-SEM analysis showed that as higher SCM concentrations on culture media higher dense nanofibers network could be prepared. Quantitative nanomechanical results obtained by AFM technique corroborate FEG-SEM analysis besides show smoother and more flexible BC membranes as a function of the increasing of the SCM concentrations. The modification of the carbon source of the culture medium with an important by-product of Brazilian agroindustry appears as a viable alternative to reduce cost of BC production (of up to 20.06%) besides increase the possibilities of industrial scale BC preparation. University of Araraquara – UNIARA Interdisciplinary Laboratory of Advanced Materials Centro de Ciências da Natureza – CNN Universidade Federal do Piauí – UFPI Institute of Chemistry – São Paulo State University – UNESP Group ‘Materials + Technologies’ (GMT) Department of Chemical and Environmental Engineering Faculty of Engineering Gipuzkoa University of the Basque Country (UPV/EHU), Plaza Europa 1 Faculty of Engineering Vitoria-Gasteiz University of the Basque Country (UPV/EHU), C/Nieves Cano 12 Laboratório de Pesquisa Desenvolvimento & Inovação, Apis Flora Ind. Coml. Ltda, Ribeirão Preto Institute of Chemistry – São Paulo State University – UNESP

Made available in DSpace on 2018-11-26T17:42:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) In this work, for the first time bacterial cellulose (BC) hydrogel membranes were used for the fabrication of antimicrobial cellulosic nanocomposites by hydrothermal deposition of Cu derivative nanoparticles (i.e. Cu(0) and CuxOy species). BC-Cu nanocomposites were characterized by FTIR, SEM, AFM, XRD and TGA, to study the effect of hydrothermal processing time on the final physicochemical properties of final products. XRD result show that depending on heating time (3-48 h), different CuxOy phases were achieved. SEM and AFM analyses unveil the presence of the Cu(0) and copper CuxOy nanoparticles over BC fibrils while the surface of 3D network became more compact and smother for longer heating times. Furthermore, the increase of heating time placed deleterious effect on the structure of BC network leading to decrease of BC crystallinity as well as of the on-set degradation temperature. Notwithstanding, BC-Cu nanocomposites showed excellent antimicrobial activity against E. coli, S. aureus and Salmonella bacteria suggesting potential applications as bactericidal films. Univ Fed Piaui, Dept Quim, Campus Minist Petronio Portela, BR-64049550 Teresina, PI, Brazil Univ Estadual Paulista, Inst Quim Araraquara, Dept Quim Geral & Inorgan, Rua Prof Francisco Degni,55, BR-14800060 Araraquara, SP, Brazil Centro Univ Araraquara, Lab Biopolimeros & Biomat BIOPOLMAT, Rua Carlos Gomes,1217, BR-14801320 Araraquara, SP, Brazil Univ Basque Country UPV EHU, Dpto Ingn Quim & Medio Ambiente, Escuela Politecn Donostia San Sebastian, Pza Europa 1, Donostia San Sebastian 20018, Spain Univ Luterana Brasil, Programa Posgrad Genet & Toxicol Aplicada, Ave Farroupilha,8001,Predio 01, BR-92450900 Canoas, RS, Brazil Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil Univ Estadual Paulista, Inst Quim Araraquara, Dept Quim Geral & Inorgan, Rua Prof Francisco Degni,55, BR-14800060 Araraquara, SP, Brazil FAPESP: 2015/ 09833-0 FAPESP: 2016/06612-6

Cellulose triacetate (CTA) based nanocomposites modified with sol-gel synthesised vanadium oxide nanoparticles (V2O5) and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-b-PPO-b-PEO or EPE) triblock copolymer were prepared by solvent vapour annealing (SVA) method. The present investigation was mainly focused on the study of the mechanical properties of designed nanocomposites from nanoscale, employing atomic force microscopy (AFM) and quantitative nanomechanical mapping (QNM), to macroscale using a universal testing machine. AFM results showed microseparated PPO domains in V2O5-EPE/CTA nanocomposites, being the sol-gel content of the nanocomposites the factor which affected the size and structure of these domains. These microphase separation affected strongly mechanical properties at both nano- and macroscale, which was especially reflected in QNM adhesion measurement. 3V2O5-EPE/CTA nanocomposite displayed the best well-ordered nanostructuration, which improved nanoparticles dispersion and enhanced both QNM and Young's modulus. Moreover, QNM modulus images enabled to measure the modulus of each microseparated phase, presenting the modulus of V2O5 nanoparticles the higher values. On the other hand, the addition of sol-gel solution provoked a maximum increment of 41% in the Young's modulus of V2O5/CTA nanocomposites if compared with neat CTA, being this increase of 32% in the case of V2O5-EPE/CTA nanocomposites, if compared with EPE/CTA blend.

Two different, molecular weight and blocks ratio, poly(ethylene-b-ethylene oxide) block copolymers (PE-b-PEO) were used as nanostructuration agent for epoxy based thermosets and as surfactant for sol-gel synthesized titanium dioxide (TiO2) nanoparticles. Obtained DSC results confirmed the miscibility of PEO block of PE-b-PEO block copolymer with epoxy monomer in PE-b-PEO/DGEBA unreactive mixtures and with DGEBA/MCDEA matrix in cured systems modified with PE-b-PEO block copolymer without or with TiO2 nanoparticles. The dilution effect caused by the addition of PE-b-PEO block copolymer on the epoxy/amine reaction mixture was verified. AFM phase images proved that nanostructured thermosetting systems can be reached in function of PE-b-PEO block copolymer content. Good dispersion and, in the case of the cured systems modified with higher molecular weight and higher PEO content PE-b-PEO block copolymer, selective localization of TiO2 nanoparticles can be achieved. The morphology of investigated thermosetting systems and the good dispersion of TiO2 nanoparticles depend on the PEO block content in PE-b-PEO block copolymer and its molecular weight. Transparent PE-b-PEO block copolymer nanostructured thermosetting systems with hydrophilic character and well dispersed or positioned TiO2 nanoparticles can be obtained.

Optical properties of novel polymer dispersed liquid crystal (PDLC) blends based on two different low molecular weight nematic liquid crystals, 4′-(hexyloxy)-4-biphenylcarbonitrile (HOBC) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA), and poly(ethylene-b-ethylene oxide) block copolymer (PE-b-PEO), were studied to develop optically reversible PDLC blends applying a temperature gradient. Differential scanning calorimetry (DSC) showed that the liquid crystals, HOBC and EBBA, maintain their nematic-isotropic transition in designed PDLC blends, which was visualized by optical microscopy (OM). Results obtained using photoluminescence and UV–vis spectroscopies indicated that HOBC and EBBA liquid crystals maintain their reversible optical behavior passing from opaque to transparent state when temperature gradient was applied. The reversible switching process was proved in four consecutive heating/cooling cycles. Designed thermo-responsive PDLC blends possessed interesting optical properties, which make them potential candidates to be use as temperature sensors or thermo-optical devices.

Conductive polyurethane foam nanocomposites were prepared by the incorporation of graphene flakes. Graphene flakes were obtained from graphite by the top-down method of liquid exfoliation in N–methyl pyrrolidone and size-selected by centrifugation. A deep characterization of graphene flakes was performed for a better understanding of their role as nanoentities in polyurethane foam matrix. Thus, morphology, with special emphasis in the number of layers, was analyzed by Raman spectroscopy, atomic force microscopy and transmission electron microscopy. Electrostatic force microscopy was used to verify the conductive nature of graphene flakes. This technique showed to be effective for the assessment of both morphology and conductive properties of graphene flakes. Regarding the electrical behavior of the nanocomposite foams, it was determined that the electrical resistance depended on both the graphene content and the compressive deformation applied to the material.

An epoxy based thermosetting matrix was modified with poly(ethylene oxide- b -propylene oxide- b -ethylene oxide) triblock copolymer, obtaining cured nanostructured thermosetting systems. Resulting systems were investigated using a novel atomic force microscopy (AFM) imaging mode, known as PeakForce quantitative nanomechanical property mapping (PeakForce QNM), that allows for the quantitative mapping of the local mechanical properties, such as adhesion and elastic modulus, together with the topography. It was demonstrated the capacity of this quantitative nanomechanical mapping to provide information on the local distribution of the elastic modulus, being able to distinguish between the mechanical properties of the two phases present in the analyzed thermosetting systems.

Made available in DSpace on 2018-12-11T17:23:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-11-05 A strain isolated from Kombucha tea was isolated and used as an alternative bacterium for the biosynthesis of bacterial cellulose (BC). In this study, BC generated by this novel bacterium was compared to Gluconacetobacter xylinus biosynthesized BC. Kinetic studies reveal that Komagataeibacter rhaeticus was a viable bacterium to produce BC according to yield, thickness and water holding capacity data. Physicochemical properties of BC membranes were investigated by UV–vis and Fourier transform infrared spectroscopies (FTIR), thermogravimetrical analysis (TGA) and X-ray diffraction (XRD). Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) were also used for morphological characterization. Mechanical properties at nano and macroscale were studied employing PeakForce quantitative nanomechanical property mapping (QNM) and dynamic mechanical analyzer (DMA), respectively. Results confirmed that BC membrane biosynthesized by Komagataeibacter rhaeticus had similar physicochemical, morphological and mechanical properties than BC membrane produced by Gluconacetobacter xylinus and can be widely used for the same applications. Laboratório de Biopolimeros e Biomateriais (BIOPOLMAT) Centro Universitário de Araraquara, Araraquara Group ‘Materials + Technologieś (GMT) Department of Chemical and Environmental Engineering Engineering College of Gipuzkoa University of the Basque Country (UPV/EHU), Plaza Europa 1 Laboratório de Pesquisa Desenvolvimento & Inovação Apis Flora Ind. Coml. Ltda, Ribeirão Preto Institute of Chemistry-São Paulo StateUniversity-UNESP Institute of Chemistry-São Paulo StateUniversity-UNESP

Bacterial cellulose (BC) produced by some bacteria, among them Gluconacetobacter xylinum, which secrets an abundant 3D networks fibrils, represents an interesting emerging biocompatible nanomaterial. Since its discovery BC has shown tremendous potential in a wide range of biomedical applications, such as artificial skin, artificial blood vessels and microvessels, wound dressing, among others. BC can be easily manipulated to improve its properties and/or functionalities resulting in several BC based nanocomposites. As example BC/collagen, BC/gelatin, BC/Fibroin, BC/Chitosan, etc. Thus, the aim of this review is to discuss about the applicability in biomedicine by demonstrating a variety of forms of this biopolymer highlighting in detail some qualities of bacterial cellulose. Therefore, various biomedical applications ranging from implants and scaffolds, carriers for drug delivery, wound-dressing materials, etc. that were reported until date will be presented.

Made available in DSpace on 2018-12-11T17:27:20Z (GMT). No. of bitstreams: 0 Previous issue date: 2016-06-05 Three different low molecular weight nematic liquid crystals (LCs) were used to impregnate bacterial cellulose (BC) film. This simple fabrication pathway allows to obtain highly transparent BC based films. The coating of BC film with different liquid crystals changed transmittance spectra in ultraviolet-visible region and allows to design UVC and UVB shielding materials. Atomic force microscopy results confirmed that liquid crystals coated BC films maintain highly interconnected three-dimensional network characteristic of BC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the three-dimensional network of BC nanofibers. Investigated BC films maintain nematic liquid crystal properties being switchable photoluminiscence as a function of temperature during repeatable heating/cooling cycles. Conductive response of the liquid crystal coated BC films was proved by tunneling atomic force microscopy measurement. Moreover, liquid crystal coated BC films maintain thermal stability and mechanical properties of the BC film. Designed thermoresponsive materials possessed interesting optical and conductive properties opening a novel simple pathway of fabrication liquid crystal coated BC films with tuneable properties. Group 'Materials + Technologies' (GMT) Department of Chemical and Environmental Engineering Polytechnic School University of the Basque Country (UPV/EHU), Plaza Europa 1 Laboratory of Photonic Materials Institute of Chemistry São Paulo State University - UNESP Laboratório de Química Medicinal e Medicina Regenerativa (QUIMMERA) Centro Universitário de Araraquara Laboratory of Photonic Materials Institute of Chemistry São Paulo State University - UNESP

Different block copolymer dispersed liquid crystals blends based on poly(ethylene-b-ethylene oxide) (PE-b-PEO) and modified with low molecular weight nematic liquid crystals, 4′-(hexyloxy)-4-biphenylcarbonitrile (HOBC) and N-(4-ethoxybenzylidene)-4-butylaniline (EBBA) were prepared and characterized. The miscibility between each block of PE-b-PEO block copolymer and nematic liquid crystals was studied using differential scanning calorimetry (DSC). DSC results were in good agreement with the miscibility prediction supported by the solubility parameters and miscibility effect in polymer dispersed liquid crystals blends based on polyethylene oxide (PEO) homopolymer. Thermal stability of PE-b-PEO/HOBC and PE-b-PEO/EBBA blends was also studied. Block copolymer dispersed liquid crystals blends maintained the nematic/isotropic transition in function of the ratio between PE-b-PEO block copolymer and nematic liquid crystals indicating the potential application of the designed materials.

The front cover glass required for photovoltaic (PV) module insulation is the first surface in receiving irradiation towards solar cell, and the first surface in limiting the photon flux impinging it due to optical losses, which can be counteracted by means of antireflective (AR) coatings. The soiling adherence inherently disrupts the intended function of the AR coatings, thus reducing the power output of the PV plants. In this work, hydrophobicity of highly antireflective layer stacks was pursued to deal against soiling adherence. Whereas antireflection property has a direct effect on the minimization of cell-to-module losses, antisoiling property reduces maintenance expenditures, both contributing to the reduction of levelized cost of energy. Properties of methyl-silylated silica and polyfluoroalkyl-silica mono- and bi-layer stacks were compared to achieve the most rational AR design based on a proper trade-off between cost-efficiency, processability, optical properties, mechanical properties and reliability during real life operation. Nanoindentation permitted to compare hardness of different coatings; cohesion and adhesion were studied by nanoscratch, both related to cleaning resistance studied by reciprocating wear test. Effect of AR layer stacks on electrical response of monocrystalline silicon cells was assessed during outdoor exposure as well as the effect of environmental relative humidity on the optical properties. Methyl-silylated silica mono-layer and polyfluoroalkyl-silica bi-layer both prepared in two-steps were the more rational designs based on adhesion, mechanical properties and abrasion resistance to cleaning process. They showed an equivalent overgeneration of 2% when applied on cover glass of PV mono-modules compared to uncoated ones along one-year exposure.

Polyfluoroalkyl-silica porous coating stacks with durable antireflection (AR) properties have been obtained for photovoltaic (PV) application. An acid-catalyzed sol-gel process combined with evaporation induced self-assembly and the presence of a non-hydrolyzable polyfluoroalkyl group linked to the central atom of the silicon alkoxide was conducted. The aim was to obtain a low surface energy coating, devised to mitigate soiling adherence, without losing the AR properties of a baseline coating. In particular, the influence of polyfluoroalkyl chain length on the thickness, the water contact angle and optical transmission properties was first analyzed. The optimized polyfluoroalkyl-silica porous coating presented low surface energy

Two different methods were employed for the preparation of cellulose triacetate (CTA) based nanocomposites without and with poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer and modified with sol-gel synthesised titanium dioxide nanoparticles (TiO2). The hybrid nanocomposites were prepared by solvent casting (SC) and solvent vapour annealing (SVA) methods. The hybrid nanocomposite films obtained by SVA presented smoother surfaces, and consequently, higher gloss values. As for transparency, only the hybrid nanocomposites prepared by SVA remained completely transparent even with high sol-gel content due to the nanostructuration of EPE triblock copolymer. Furthermore, the UV-shielding properties provided by the TiO2 nanoparticles were not modified regardless of the employed preparation method. Finally, the nanocomposites prepared by SVA presented a higher Young's modulus and tensile strength than the SC nanocomposites. The obtained results proved the efficiency of the SVA method to control the relationship between the morphology and the final properties of the hybrid nanocomposite films leading to materials with enhanced surface, optical, and mechanical properties.

Biodegradable films for food packaging have received increasing attention from the industry in recent years. Due to its extraordinary properties, chitosan has demonstrated to be an exceptional candidate for that kind of applications. In this study, chitosan-based films modified with an azopolymer and silver nanoparticles were prepared by solvent-casting. The quality and homogeneity of the samples was satisfactory and films with thicknesses of the order of 25 µm and of various sizes, with diameters ranging from 5 to 15 cm, were obtained. The developed hybrid films were characterized by several experimental techniques including: atomic force microscopy, attenuated total reflectance-Fourier transformed infrared spectroscopy, thermogravimetric analysis, ultraviolet–visible spectroscopy and water contact angle measurements. In addition, the mechanical properties of the samples were investigated. Specifically, the tensile strength and the elastic modulus were enhanced in the films modified with azopolymer and silver nanoparticles. Moreover, the developed films showed reversible induced birefringence properties, indicating that they could be used for optical storage applications.

Photoresponsive multilayer films consisting of alternating layers of chitosan and an azopolymer were developed by layer-by-layer self-assembly. The influence of the pH and the number of bilayers on the structure and properties of the films was investigated by different experimental techniques.

Thermosetting systems based on DGEBA epoxy resin and poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (EPE) triblock copolymer were prepared and investigated. Different mixtures were obtained by using different contents of EPE block copolymer in order to study the influence of the modifier on the properties of the final materials. All thermosetting systems were prepared without using any solvent and were cured at ambient temperature, taking into account the lower critical solution temperature (LCST) behavior of the block copolymer. DSC results indicated that the addition of block copolymer affected to the curing reaction time and to the glass transition temperature of the mixtures and also the miscibility of EPE triblock copolymer in the epoxy resin was proved. The morphologies studied by AFM and TEM showed clear nanostructuration up to 25 wt % EPE content. The addition of 5 and 15 wt % of EPE block copolymer led to a considerable improvement in the toughness of the materials. When EPE block copolymer was added to the epoxy resin, the surface became more hydrophilic and the UV–vis transmittance decreased slightly maintaining a high level of transparency.

PEO-b-PPO-b-PEO block copolymer (EPE20) was used as both nanostructuring agent for unsaturated polyester (UP) matrix and dispersing agent for sisal microfibrillated cellulose (MFC), which successfully reduced the brittles of the UP matrix increasing the toughness of designed materials and allowed to maintain the flexural modulus in the UP/EPE20/MFC. Sisal MFC, prepared by chemical and mechanical treatment using high pressure homogeneizer, was employed as reinforcement for nanaostructurated UP based thermosetting systems. UP system modified with both 1 wt.% MFC and 5 wt.% EPE20 led to design optically transparent nanostructured thermosetting materials with good mechanical properties. 2013 Elsevier Ltd. All rights reserved.

The aim of this contribution was the study of the influence of polymer matrix on the photo-induced orientation of azobenzene groups. Notably, an azo-prepolymer bearing hydroxyl groups was selectively confined in self-assembled phases of different block copolymers, randomly-epoxidized polystyrene-b-polybutadiene-b-polystyrene (SBSep) and polystyrene-b-poly-4-vinylpyridine (S4VP). The formation of hydrogen bonds between the azo-prepolymer and poly-4-vinylpyridine block, as well as the effect of the local environment surrounding the azo-prepolymer were investigated by Fourier transform infrared and ultraviolet–visible spectroscopies. In addition, the reversible optical storage properties of the developed materials were also studied. Birefringent properties of the systems based on S4VP were strongly enhanced by intermolecular interactions with the azo-prepolymer. Specifically, the maximum birefringence level attained by a system containing 13 wt% of azobenzene was around 2.3 × 10−2 and its remaining birefringence was nearly three times higher than that of the neat azo-prepolymer. Furthermore, a morphological analysis of the designed materials was carried out by atomic force microscopy. Taking into account that the control of the microdomains ordering in block copolymer films is of current interest, special attention was focused on the influence of different variables on the arrangement of the block copolymer microdomains.

Many efforts in the field of azobenzene-containing polymers are concentrated on exploring new material concepts to obtain efficient and stable photo-induced anisotropy. Here, an easy approach to improve the birefringent properties of an epoxy-based azo-prepolymer is reported. The designed azo-prepolymer was selectively confined in a self-assembled domain of a block copolymer and thanks to the formation of hydrogen bonds a major enhancement of its optical response was achieved. In particular, the resulting material presented double the maximum level of optical anisotropy of the neat azo-prepolymer and nearly 80% of remaining birefringence.

Miscibility, crystallization and morphology of unsaturated polyester (UP) matrices, nanostructured with a poly[(ethylene oxide)- b -(propylene oxide)- b -(ethylene oxide)] (PEO- b -PPO- b -PEO) block copolymer (BCP) from 0 to 50 wt% has been investigated. Additionally, the role of each block on miscibility and morphology of cured mixtures was studied. Behaviours of non-reactive mixtures of UP thermosetting precursor with two BCPs composed of similar and strong immiscible central PPO block were compared. It was found that one BCP had PEO blocks with not enough molecular weight to compatibilize the PPO block with the UP thermosetting precursor at room temperature. Transmitted light intensity study of mixtures indicated that during curing at 35 °C no macrophase separation took place, contrary to the systems cured at temperatures equal or higher than 60 °C. Curing mixtures at 35 °C produced nanostructured matrices with almost unchanged transparency. Phase separation and miscibility of BCP with UP matrix were measured by means of DSC and DMA. AFM analysis showed worm-like morphology with diameters from 10 to 20 nm and length that evolved from 50 nm to 1 μm with increase of BCP content.

Microphase separated epoxy-based materials modified with an amphiphilic poly(styrene-block-ethylene oxide) diblock copolymer (PS-b-PEO) with low amount of PEO-block as well as ternary systems modified with this block copolymer and containing via sol–gel in situ synthesized TiO2 nanoparticles were prepared and characterized. The obtained results indicate that block copolymer had enough amount of PEO-block in order to achieve microphase separated materials for a high range of PS-b-PEO contents, morphologies changing from spherical micelles to long wormlike micelles passing through vesicles upon increasing copolymer amounts. In the case of 20 wt.% inorganic/organic epoxy-based materials, addition of synthesized TiO2 nanoparticles into PS-b-PEO-(DGEBA/MCDEA) system led to location of the nanoparticles in PEO-block/epoxy-rich confined between two microphase separated PS-block-rich phases. Designed highly transparent multiphase inorganic/organic epoxy-based materials possess interesting specific properties such as high UV shielding efficiency and high water repellence.