A reexamination of the crystal structure of phase II of poly(vinylidene fluoride)

Abstract

The crystal structure of phase II (a phase) of poly(vinylidene fluoride) was studied by reexamining the work of earlier investigators. The reflections of phase II can be indexed to an orthorhombic unit cell with lattice parameters a = 0.496 nm, b = 0.964 nm, and c (chain axis) = 0.462 nm. There are two chains in this unit cell. The two chains pack with the chain dipole moments antiparallel. Three different ways of packing the chains, with respect to chain sense, were studied: both chains up, one up and one down, and a statistical up-down packing. It was found that to within a 96% confidence level, the chains pack with a statistical up-down packing.

Vinylidene fluoride telomers for piezoelectric devices

“…Thus, PVDF has been used in high-tech applications, such as [1][2][3] paints and coatings, medical suture wires, mechanical substrates for fuel cell membranes, liners for containers used to carry corrosive substances (for example, bromine), separators for lithium ion batteries and backsheets for photovoltaic cells. In addition, PVDF is a piezoelectric polymer, 4,5 and pressure or mechanical stress can induce an electrical response.…”

Phase transition in the surface structure in copolymer films of vinylidene fluoride (70%) with trifluoroethylene (30%)

“…The ferroelectric ␤ phase is usually observed below a ferroelectric Curie temperature ͑that is higher for higher VDF content͒ following poling with a high electric field and mechanical drawing to convert the chain conformation from the nonpolar ␣ phase. 13,14,20 The ␣ phase consists of an alternating trans ͑T͒ gauche ͑G͒ bonding configuration ͑or TGTḠ pattern͒ arranged in a nonpolar, paraelectric, structure. 13,14,20 The weakly polar ␦ and ␥ phases and other nonpolar phases ͑particularly the helical phase of polyethylene and other hydrogen-rich compositions͒ are not known or expected to take part in a ferroelectric transition.…”

“…13,14,20 The ␣ phase consists of an alternating trans ͑T͒ gauche ͑G͒ bonding configuration ͑or TGTḠ pattern͒ arranged in a nonpolar, paraelectric, structure. 13,14,20 The weakly polar ␦ and ␥ phases and other nonpolar phases ͑particularly the helical phase of polyethylene and other hydrogen-rich compositions͒ are not known or expected to take part in a ferroelectric transition. [12][13][14][15][16][17][18][19][20][21][22] Surface structures can be different from bulk even if compositionally the same.…”

“…13,14,20 The weakly polar ␦ and ␥ phases and other nonpolar phases ͑particularly the helical phase of polyethylene and other hydrogen-rich compositions͒ are not known or expected to take part in a ferroelectric transition. [12][13][14][15][16][17][18][19][20][21][22] Surface structures can be different from bulk even if compositionally the same. This is true of both the clean semiconductor surfaces that exhibit surface structural transitions related to the surface nonmetal to metal transition that occur with increasing temperature 11 and the surface reconstructions in metals that undergo a surface-temperature-dependent structural transformation, as noted for Mo͑100͒, 2 Mo͑112͒, 5 and W͑100͒.…”

Crystalline structure and molecular mobility of PVDF chains in PVDF/PMMA blend films analyzed by solid-state 19F MAS NMR spectroscopy

“…[1][2][3][4] The main chain conformations of the a-, b-and g-forms are tg þ tg À , all-trans (tttt), tttg þ tttg À , respectively. The melting temperatures (T m ) vary in the range of 170-190 1C depending on the crystalline polymorphs.…”