Abstract
Abstract The first 20 members of the homologous S-cholesteryl alkyl thiocarbonates were prepared from cholesteryl chlorothiolcarbonate and l-alkanols. We identified the mesophases by optical means and determined the temperatures and heats of transitions with a differential scanning calorimeter. All members of this series exhibit a cholesteric mesophase and, except for the first three members, a monotropic smectic mesophase. The temperature range between the smeetic-cholesteric and the cholesteric-isotropic mesophase transitions decreases with increasing chain length. It reaches about 10° for S-cholesteryl decyl thiocarbonate and remains constant for higher homologs. S-Cholesteryl butyl thiocarbonate and its higher homologs display the visible spectrum of selectively reflected light. The temperature interval of this color band is less than 0.1° for the S-cholesteryl undecyl through heptadecyl thiocarbonate.
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