Abstract
PVT‐measurements on atactic polystyrene shows that the Ehrenfest equations, which describe a thermodynamic transformation of the second order, are not applicable for the glass transition. The introduction of one internal ordering parameter ζ in addition to the conventional variables T and P, is sufficient to describe the behaviour in case of atactic PS in the isotropic glassy state. The usually observed way dependences in the glassy state can be explained by the concept of ordering parameters.
In recent years liquid crystalline side chain polymers were developed. The liquid crystalline phases of these polymers can be supercooled and frozen‐in like isotropic liquids. As the nematic or smectic liquid crystalline structure freezes‐in, and can be conserved by this process, glasses with anisotropic properties are obtained. These glasses show e.g. a high optical birefringence.
The glass transition of the liquid crystalline polymers can only be described by the assumption of at least two parameters ζ~i~. Therefore the Ehrenfest equations are not applicable for the glass transition of isotropic as well as anisotropic glasses.