Molecular design of cellulosic thermotropic liquid crystals

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From the results of this former research period, it was found that it is indispensable to establish the synthetic method for cellulose for investigating the relationship between structure and property of cellulosic liquid crystals. At present, the regiospecific introduction of the desired functional groups into the 2-or 3-position of cellulose is impossible, but this may be possible by the chemical synthetic method of cellulose. We established the chemical synthetic method cellulose in last year. In this year, we first of all investigated the substituent effect on the polymerization to clarify the reaction mechanism. It was found that 3-O-benzyl group is indispensable for the stereo-and regioregularity, and 2-O-pivaloyl group for regiospecific polymerization. We also succeeded in the stepwise synthesis of celloeicosaose with DP 20. Thus, the method yielding regiospecific substituted cellulose derivatives was established. Then, 2-propyl cellulose was first synthesized as an example. Consequently, it is indicated that the present synthetic method is useful for getting 2-O-alkyl and, probably, also 2-acylated cellulose derivatives. The solubility and thermal behavior of 2-propyl cellulolse were examined resulting several interesting findings. Thus the method for accumulating basic knowledge about cellulosic liquid crystalline properties was established.