Order parameter measurements in polypeptide liquid crystals

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Abstract
An analysis of x-ray scattering from magnetically oriented liquid crystalline solutions of poly-γ-benzyl-L-glutamate (PBLG) in dioxane yields a value for the order parameter S?0.75. At the isotropic–liquid crystal phase transition, the critical order parameter Sc?0.5 appears to agree with predictions of mean-field theory. Away from the transition, S is independent of PBLG concentration and PBLG axial ratio but does decrease when the helix denaturing agent trifluoroacetic acid is added to the liquid crystal. The magnitude of and changes in S are discussed in terms of the inherent flexibility of helical synthetic polypeptides.