DYNAMIC-MECHANICAL PROPERTIES OF CYCLOHEXANE-BASED GLASS-FORMING LIQUID-CRYSTALS AND A LINEAR SIDE-CHAIN POLYMER ANALOG

A nematic and a cholesteric liquid crystal, both derived from trans-1, 3,5-cyclohexanetricarboxylic acid, and a linear side chain polymer ana logue were characterized in terms of storage (G') and loss (G '') modu li as functions of frequency and temperature. It was found that all th ree model compounds show a shear shinning flow behaviour with zero she ar viscosities of the low molar mass systems significantly less than t hat of the polymer system at the same reduced temperature, T/T-g. With shift factors prescribed by the WLF equation, both the G' and G '' da ta of all three compounds are adequately represented by master curves. Furthermore, within the framework of the stretched exponential model, the relaxation behaviours of the low molar mass systems are well desc ribed by a single Maxwell element, whereas the polymer system shows a relatively broad distribution of relaxation times. The observed viscoe lastic properties suggest a relative ease of material processing of th e low molar mass systems compared to the polymer analogue due to a low er zero shear viscosity and a single relaxation time characterizing th e dynamics of response to a mechanical or thermal stimulus.