A new idea to understand the macromolecular motion occurring along the thermal relaxations of polystyrene (PS) and PS-barium titanate composites is proposed. Detailed analysis of PS infrared bands provides a better knowledge of the factors affecting polymer dynamics. Average spectral positions and integrated absorbance of bands in the region of C-H out-of-plane vibrations showed a continuous decrease with temperature, whereas those in the region of aliphatic and aromatic C-H stretching vibrations showed the sharpest changes with temperature. Relaxation temperatures were determined from the changes observed in the band wavenumber or area with temperature. These results were attributed to changes in the distribution of the phenyl π-electron cloud, causing important dipole moment variations in the different vibration modes when the thermal transitions are taking place. Finally, although the presence of BaTiO3 particles does not seem to exert any specific effect on the PS dynamics in the glassy state, the Curie transition of these particles might induce a kind of confinement effect observable by FTIR.

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This work offers a new vision of the nanoparticle-polymer interface in inorganic nanoparticle filled thermoplastic nanocomposites in terms of macromolecular structure, conformations, and interactions. In particular, the molecular structure and interfacial conformation of PMMA in silica/PMMA nanocomposites obtained by high-energy ball milling (HEBM) have been studied. HEBM was applied to achieve an extraordinary dispersion of high content of silica nanoparticles within the PMMA polymer. Fourier transform infrared spectroscopy (FTIR) was used to investigate the effect that the important shear forces imposed by the HEBM process has on the PMMA structure and its dynamics and also the effect of the presence of silica nanoparticles inserted by HEBM on the particular conformations of PMMA appearing at the interface. It has been demonstrated that HEBM induces particular conformational changes on both the ester group and the backbone of the PMMA, which seem to be the cause of subsequent appearance of specific polymer chain packing at the interface.

Sizing glass fibers with silane coupling agents enhances the ad-hesion and the durability of the fiber/polymer matrix interface in composite materials. There are several tests to determine the inter-facial strength between a fiber and resin, but all of them present difficulties in interpreting the results and/or sample preparation. In this study, we observed the influence of different aminosilanes fiber coatings on the resistance of epoxy-based composite materials using a very easy fractographic test. In addition, we tried a new flu-orescence method to get information on a molecular level precisely at the interface. Strength was taken into account from two stand-points: (i) mechanical strength and (ii) the resistance to hydrolysis of the interface in oriented glass-reinforced epoxy-based composi-tes. Three silanes: γ -aminopropyltriethoxysilane, γ -Aminopropyl-methyldiethoxysilane, and γ -Aminopropyldimethylethoxysilane were used to obtain different molecular structures at the interface. It was concluded that: (i) the more accessible amine groups are, the higher the interface rigidity is; (ii) an interpenetrating network mechanism seems to be the most important for adhesion and there-fore to the interfacial strength; and (iii) the higher the degree of crosslinking in the silane coupling layer is, the higher the hydrolytic damage rate is.

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We report the preparation of a nanocomposite hydrogel based on a poloxamine gel matrix (Tetronic T1107) and cyclodextrin (CD)-modified barium titanate (BT) nanoparticles. The micellization and sol-gel behavior of pH-responsive block copolymer T1107 were fully characterized by small-angle neutron scattering (SANS), dynamic light scattering (DLS), and Fourier transform infrared attenuated total reflectance (FTIR-ATR) spectroscopy as a function of concentration, pH and temperature. SANS results reveal that spherical micelles in the low concentration regime present a dehydrated core and highly hydrated shell, with a small aggregation number and size, highly dependent on the degree of protonation of the central amine spacer. At high concentration, T1107 undergoes a sol-gel transition, which is inhibited at acidic pH. Nanocomposites were prepared by incorporating CD-modified BT of two different sizes (50 and 200 nm) in concentrated polymer solutions. Rheological measurements show a broadening of the gel region, as well as an improvement of the mechanical properties, as assessed by the shear elastic modulus, G' (up to 200% increase). Initial cytocompatibility studies of the nanocomposites show that the materials are nontoxic with viabilities over 70% for NIH3T3 fibroblast cell lines. Overall, the combination of Tetronics and modified BaTiO3 provides easily customizable systems with promising applications as soft piezoelectric materials.