Glass transition temperatures, poly -liquid-crystalline polymer

Differences in tacticity were also reflected by thermal data. While the iso-tropization temperature of (-)-poly-(IV-ll) and ( )-poly-(IV-ll),synthesized using initiator 1, stayed approximately unchanged, the isotropization temperatures for the chiral liquid crystalline polymers shifted to higher values when initiators 2 or 3 were used. The difference was up to 7 °C. If the decreased glass transition temperatures (Tg) for the chiral analogues were taken into account, the temperature range of the liquid crystalline phase was broadened by up to 12 °C. This means that a certain diad must be responsible for this behavior. The authors assumed that the diad cmHT was most suitable one for the formation of stable liquid crystalline phases in poly(norbornene) main chains. 

At this point, we would like to mention again that the polymer PE-H in Table 3.14, poly-2,5-di(benzoyloxy)styrene, was first synthesized some 40 years ago as a precursor of an electron exchange polymer (Ezrin et al., 1953). In this study we were lucky to have found that this polymer is liquid crystalline at temperatures above its glass transition (Table 3.14). To our knowledge PE-H is probably the oldest thermotropic liquid crystalline polymer ever synthesized by chemists. 

Some polymers may undergo transitions above the glass transition temperature, which Boyer [224] called intermediate transitions at T > Tg for amorphous polymers and T, < T < T for crystalline amorphous polymers. Gas chromatography has demonstrated such a transition in poly(vinyl chloride) [205] it was attributed, as in liquid crystals, to the existence of a state with nematic order at temperatures between T, and... 

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