Conformational Energies of Perfluoroalkanes. III. Properties of Polytetrafluoroethylene

Abstract

Properties of polytetrafluoroethylene which depend on the configurational statistics of the chain are discussed in terms of the four-state rotational-isomeric model used in the preceding paper to correlate the dipole moments of H(CF2)nH. Solution and melt viscosities are calculated from the predicted characteristic ratio, 〈r2〉0/nl2= 30 ± 15 at 600°K, and are in satisfactory agreement with experimental data. The temperature coefficient d In 〈r2〉0/dT is predicted to be -(0.9 ± 0.5) X 10-3deg-1. The thermodynamics of both the solid-solid and solid-liquid phase transitions of the polymer are consistent with the four-state model. The calculated conformational entropy change on melting is 0.8 ± 0.1 cal deg-1mole-1, in good agreement with the experimental constant volume entropy of melting of 0.76 cal deg-1mole-1. © 1968, American Chemical Society. All rights reserved.