Materials Chemistry and Physics, Vol.223, 140-144, 2019
Evidence of local softening in glassy poly(vinyl alcohol)/poly(vinyl pyrrolidone) (1/1, w/w) nano-graphene platelets composites
Complex permittivity studies on glassy poly(vinyl alcohol)/poly(vinyl pyrrolidone) (1/1) at proper pressure-temperature condition, provide the activation volume and energy values for both dc conductivity and beta-relaxation. The temperature dependence of the activation volume, which signatures volume-fluctuations accompanying a dynamic process, maximizes at temperature near the glass transition temperature of neat polyvinyl alcohol. The phenomenon is interpreted by a local softening of polyvinyl alcohol domains, while the blend remains in its glassy state. The scenario is also supported by the dependence of the activation energy upon pressure. Dispersed nano-graphene platelets at volume fractions around the critical conductivity percolation threshold are comparatively studied, so as to determine whether local softening affects the formation of a conductivity percolation network.
Keywords:Dielectric spectroscopy;poly(vinyl alcohol);poly(vinyl pyrrolidone);Nano-graphene platelets;Glass transition