New polymer synthesis .83. Synthesis of chiral and cholesteric polyesters from silylated ''sugar diols''

A series of polycondensation was conducted with the purpose to optimize the reaction conditions for the polycondensation of silylated 2,3-isopropylidene D-threitol with a dicarboxylic acid dichloride. Polycondensation in o-dichlorobenzene or 1-chloronaphthalene at 180-230 degrees C were found to be most satisfactory. Trifluoroacetic acid/H2O allow an easy cleavage of the isopropylidene group without hydrolysis of the polyester. Ten cholesteric copolyesters were prepared by polycondensation of mixtures of silylated methylhydroquinone and isosorbide, isomannide, or 2,3-isopropylidene threitol with the dichloride of 1,10-bis(4'-carboxyphenoxy)decane. All these copolyesters form a broad cholesteric phase above 200 degrees C. The copolyesters containing 5 or 10 mol % of a sugar diol display a blue Grandjean texture. (C) 1996 John Wiley & Sons, Inc.