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

Abstract

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 polymer-solvent 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 a 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 2θ = 22.2°and 24.0° 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.