Abstract
The flow birefringence method has been used to investigate sulphuric acid solutions of the two series of polyhydroxyphenylbenzoxazoleterephthalamides differing as to the position of the phenyl ring ( para- or meta-) in the chain. On the basis of the method, using the Tsvetkov theory of flow birefringence we obtained, as a result of quantitative evaluations, values for the optical anisotropy of the monomer unit Δa = (330 ± 30) × 10 −25 cm 3 and the Kuhn segment length A = (330 ± 30) and (115 ± 20) Å for the para- and meta-isomers respectively. An analysis of flexibility mechanisms for the chains of both monomers gives theoretical values of the rigidity parameter A that are in keeping with the experiment values, thus substantiating validity of the molecular models being used.
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