The annealing of solution grown crystals of alpha and gamma poly(vinylidene fluoride)

摘要

Single crystals of poly(vinylidene fluoride) PVF2have been grown from dilute solution and sedimented to form oriented mats. The product was agr;hyphen;PVF2or a mixture of agr;hyphen; and ggr;hyphen;PVF2and different morphologies were observed for the two phases. Annealed mats exhibited complex melting behavior, due in part to melting and recrystallization. Plots of melting temperature against reciprocal lamellar spacing indicate equilibrium melting points of 443.5 and 457.3 K for rapidly crystallized agr;hyphen; and ggr;hyphen;PVF2after 1hyphen;h anneal, and fold surface free energies of 15.6 and 27.2 mJmminus;2for agr;hyphen;PVF2from different solvents, 24.8 mJmminus;2for ggr;hyphen;PVF2. Long annealing times or high annealing temperatures tend to increase the melting point without changing the lamellar thickness probably due to rejection of headhyphen;tohyphen;head defects.