Thermoreversible supramolecular organization in poly(vinylidene fluoride)-dodecyl benzene sulfonic acid blends

Abstract

Blends of poly(vinylidene fluoride) (PVF₂) and dodecyl benzene sulfonic acid (DBSA) were found to phase separate in the melt state from hot-stage polarizing optical microscopy and differential scanning calorimetry (DSC). Both these studies also indicated the formation of a reversible mesomorphic order in the DBSA-rich phase of the blends. Scanning electron microscopy (SEM) showed a fibrillar network morphology of the DBSA-rich phase. Wide-angle X-ray diffraction (WAXD) revealed the formation of a lamellar structure in the blends corresponding to a long period of 26 Å. The mesomorphic nature of the blends is believed to arise from the supramolecular organization of the surfactant molecules within the lamella. Thermal study indicated that the supramolecularly organized complex is the VF₂ monomer unit:DBSA ≈ 4:1, and the enthalpy of complexation is ~723 J mol⁻¹.