Abstract
Properties of polyesters based on 4,4′-dihydroxy-2,2′-dimethylazoxybenzene and a homologous series of alkanedioic acids with methylene sequence length n=3—4 are discussed in the light of recent results based on DSC, PMR, magnetic birefringence and X-ray data. Influence of substitution in the mesogen and spacer is also described. Particular attention is given to the oddeven effect in the homologous series and the existence of two distinct levels of molecular order for the n=even and n=odd members of the series. On the basis of X-ray diffraction data performed on oriented samples, a cybotactic micellar model for the n=even polymers is proposed. The cooperative nature of the formation of cybotactic micelles is shown by the study of order parameter and its dependence on the degree of polymerization. Progressive development of layered order in n=even polymers with increase in molecular mass is also shown by SAX patterns of unoriented samples of poly(4,4′-dioxy-2,2′-dimethylazoxybenzenedodecanedioyl). While the Meier and Saupe theory of the nematic state is in good agreement with the S(T) dependence for noncybotactic polymer systems for most of the nematic interval, it diverges in the vicinity of the clearing point. In contrast to low molecular mass nematics, polymeric nematics show a remarkable stability at the clearing temperature and a large pretransitional interval.
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Blumstein, A. Nematic Order in Polyesters with Flexible Moieties in the Main Chain. Polym J 17, 277–288 (1985). https://doi.org/10.1295/polymj.17.277
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DOI: https://doi.org/10.1295/polymj.17.277
