Influence of chain structure and molecular weight of poly(vinylidene fluoride) on the morphology of its thermoreversible gels in acetophenone, ethyl benzoate, and glyceryl tributyrate

Abstract

The morphology of thermoreversible gels of three commercial poly(vinylidene fluoride) (PVF₂) samples in the three solvents acetophenone (ACTP), ethyl benzoate (EB), and glyceryl tributyrate (GTB) are studied by means of scanning electron microscopy (SEM). The PVF₂/ACTP gels have a spheroidal morphology, the PVF₂/GTB gels have a fibrillar morphology, and the PVF₂/EB gels have a mixed morphology containing both the fibrillar and the spheroidal texture. The fibrillar and spheroidal radii increase with increasing gelation temperature and polymer concentration. At identical gelation condition the radii decrease with increasing head to head (H-H) defect structure in the polymer chain and also with increasing molecular weight. These results are explained with the nucleation and growth mechanism of polymer crystals in solution. It is concluded from this study that though a polymer/solvent compound formation is responsible for the fibrillar morphology it does not affect the nucleation and growth process controlling the radii of spheroids and fibrils.