Rotational energetics in vinyl polymer liquids: 2. Other polymers

Abstract

The procedures described for poly(vinyl acetate) in the preceding paper are applied to compute the effects of pressure on the Vogel T 0 and B between P∗ = −b ( Tait) and P = 2000 bars for polystyrene, linear polyethylene, polyisobutylene, and polydimethylsiloxane. From these are derived the pressure dependences of the rotational energies U and V, where U is the energy difference between the rotational states and V is a rotational barrier. The U∗ for the ‘isolated’ chain is corrected by the factor Z∗, which appears to be an intramolecular cooperative unit, to yield U∗∗, the energy difference between the rotational states for a single main-chain bond in the ‘isolated’ chain. A major conclusion of this work is that statistical mechanical calculations of the conformational (i.e. rotational) properties using ‘isolated’ chain values for U will give erroneous results when applied to the real polymer liquid. The same conclusion based on a different approach has been reported previously.