Thermodynamics, morphology, and structure of the poly(vinylidene fluoride)-ethyl acetoacetate system

摘要

The poly( vinylidene fluoride) (PVF2)-ethyl acetoacetate (EAA) system produces polymer-solvent compounds. The temperature-concentration phase diagram and the Tamman's diagram indicate that the polymersolvent complexes are of two different types which are stable in different temperature regions; one is a congruently melting compound while the other is of the singular type. Also, a metatectic-like behavior is observed due to the peculiar melting behavior of PVF2. The morphology of the compounds resembles a "crumpled cloth" network, with the probable presence of chain-folded lamellae. SAXS study indicates presence of chain-folded lamellae of lamellar thickness 8 nm in the PVF2-EAA systems. FTIR and WAXS spectra indicate formation of R polymorphic structure of PVF2, and they are consistent with the occurrence of compounds. Indeed, two new X-ray diffraction peaks are observed for the system at 2 theta = 22.2 degrees and 24.0 degrees near the polymer- solvent complex stoichiometric composition (W-PVF2 = 0.33). The FTIR spectrum also shows a new peak at 592 cm(-1) for the complex formation at the stoichiometric composition. Molecular modeling using the MMX program supports the polymer- solvent complexation in this system.