Side-chain liquid-crystalline polysiloxanes containing ionic mesogens and cholesterol ester groups

A series of ionic liquid-crystalline polysiloxanes were synthesized in a one-step reaction by using cholest-5-en-3-ol(3β)-10-undecenoate and potassium 2-allyloxy-5-cholesteryloxycarbonyl-benzenesulfonate, which contain potassium ion between 0 and 1.05 wt%. The content of potassium ion was characterized by spectrophotometric analysis using sodium tetraphenylboron as titrant. All the polymers showed thermotropic liquid crystal properties. All the samples showed cholesteric mesophase, while the sample with more ionic mesogens displayed smectic mesophase and cholesteric mesophase. With the increase of ionic groups in the polymers, the temperatures of glass transition and clear point change a little, and the enthalpy changes of melt increase with increase of ionic content of the polymers. Reflection spectra of cholesteric mesophase of the series of polymers showed that the reflected wavelength becomes broad and shifts to long wavelength with increase of the ionic mesogens in the polymer systems, suggesting that helical pitch P become long.