Double Glass Transitions and Interfacial Immobilized Layer in in-Situ-Synthesized Poly(vinyl alcohol)/Silica Nanocomposites

The results of dynamic mechanical analysis (DMA) revealed that there were double tan 6 peaks in tile poly(vinyl alcohol)(PVA)/silica nanocomposite samples at low frequencies. The two relaxations attribute to glass transition for PVA matrix and motions of segments for PVA chains confined by the surface of silica nanoparticles, respectively. The thickness of the interfacial immobilized layer was calculated, and. schematic models were founded, which can well interpret tile results. The changes of the two relaxations with various silica contents at different frequencies are discussed. It is considered that most of the interfacial PVA chains probably span the two layers. The peak position of the first relaxation moves to high temperature With the increase of frequency for strain tag of the sample whereas tile second one shifts to low temperature for tile drag effect between the intrinsic and interfacial segments of the spanned PVA chains.