Nanocomposites of poly(vinylidene fluoride) with organically modified silicate

Using Gaussian peak fitting of WAXS profiles, we determine that the composition range can be divided into three parts. First, for OMS greater than 0.5 wt%, alpha phase fraction, ϕalpha, is insignificant (ϕalpha∼0-0.01). Second, at the intermediate range, for OMS between 0.5 wt% down to 0.025 wt%, beta phase dominates and the beta fraction, ϕbeta, is related to alpha by ϕbeta>ϕalpha. Third, below 0.025 wt% OMS, alpha dominates and ϕalpha>ϕbeta. The ability of small amounts of OMS (≥0.025 wt%) to cause beta crystal domination is remarkable. Overall, crystallinity index (from the ratio of WAXS crystal peak area to total area) ranges from about 0.36 to 0.51 after cold crystallization. Real-time WAXS studies during heating of initially cold crystallized nanocomposites show that there is no inter-conversion between the alpha and beta phase PVDF crystals, where these crystals coexist at room temperature. While all samples showed a strong SAXS Bragg peak, indicating existence of two-phase lamellar stacks, the sample containing predominantly beta phase had poorly correlated lamellar stacks, compared to samples containing predominantly alpha phase.