Synthesis and characterization of main chain thermotropic liquid crystalline polyurethanes and polyesters containing biphenyl mesogens based on AB-type sel

In this thesis, we have carried out a systematic study wherein the nature of the connecting group to the mesogens was varied in order to study its effect on the mesophasic characteristics in case of biphenyl containing polmers synthesized via an AB approach. The synthesis and characterization of thermotropic liquid crystalline polyurethanes containing biphenyl mesogens in the main chain were done, for the first time, using an AB-type self-polycondensation approach. The in-situ generation of isocyanate functionality was achieved by using carbonyl azide as protecting groups to overcome the problem of synthesizing the unstable AB monomer (hydroxy isocyanate). The SmA phase of these polyurethanes was analyzed thoroughly by DSC, OPM, XRD and FT-IR studies. The synthesis of polyurethanes having similar structural relationship as that of PU-n was then carried out using A2 + B2 approach to study the effect of connectivity. More Info

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