A scheme for phase stability in liquid crystal polymers

It is shown that conditions for realizing mesomorphic states in polymers are readily expressed in terms of the relative thermodynamic stabilities of the crystalline, liquid crystalline, and liquid phases. The simple scheme presented here has the merit of providing: (i) a unifying perspective over a wide range of mesophase behaviour that otherwise may be considered in isolation as disconnected occurrences, and (ii) a signpost for purposeful attainment (or enhancement) of the mesomorphic state also in the case of systems that are not normally considered liquid crystal forming. Examples are quoted from a range of materials, most comprehensively from polyethylene, bringing together diverse past and some rather striking new observations illustrating the validity and usefulness of the scheme.