Dielectric Study of the Effect of a Sol‐Gel Inorganic Network on Polymeric Relaxation Dynamics in Acrylic/Titania Hybrids

Abstract

In this research, poly[(methyl methacrylate)-co-(butyl methacrylate)-co-(methacrylic acid)]/TiO 2 hybrids were prepared by the sol-gel process. The copolymer composition was 16 mol-% methyl methacrylate (MMA), 80 mol-% butyl methacrylate (BMA) and 4 mol-% methacrylic acid (MA). The dielectric properties of the hybrids with varying titania content were measured over the frequency range 0.1 Hz to 100 kHz and between 25 and 160 8C. In addition, the hybrids were investigated using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). In the given frequency range, a single relaxation peak was observed both by dielectric relaxation spectroscopy (DRS) and DMTA. The single relaxation observed by DRS behaves in the manner of an a-relaxation, with the frequency-temperature locus showing non-Arrhenius behavior (curved downwards like a VTF law). The change in the DRS and DMTA characteristics in hybrids compared to the pure polymer reflect the presence of antagonistic mechanisms controlling the dynamics of the polymer chains: nanodomains with enhanced and restricted mobilities are suggested to be responsible for the broadening of the isochronal dielectric loss curve toward, respectively, the low and the high temperature sides. Combining the DSC and DRS results, it can be inferred that the domains with enhanced mobility result from internal and external plasticization effects that reduce the intermolecular hydrogen bonds between the polymer chains. Besides, the motion of polymer chains is found to be significantly hindered by the titania network, due to the presence of iono-covalent bonds between the polymer and titania and geometrical restrictions in high junction-point density and titania-rich microphases. From the Arrhenius plot, it is also shown that the addition of sol-gel titania more severely hinders the segmental motion of the macromolecular chains than the local motion of the lateral groups (b relaxation).Simplified schematic morphology for the poly(MMA-co-BMA-co-MA)/TiO 2 hybrids.

New biodegradable blends prepared from polylactide, titanium tetraisopropylate, and starch

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Surface modification of TiO2nanoparticles and preparation of TiO2/PDMS hybrid membrane materials

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Thermal and morphology properties of various silica contents in sulfone epoxy nanocomposites

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