Thermal and dynamic-mechanical properties of new chiral smectic networks

The thermal and dynamic-mechanical behavior of two chiral liquid-crystalline networks are described. Both polymer networks formed a smectic mesophase whose isotropization temperature and enthalpy decreased with increasing crosslinking degree. The dynamic-mechanical behavior was studied in the linear viscoelasticity range. Three main relaxation regions were assigned to the β relaxation, the α network relaxation and the isotropization. Thus, it was possible to monitor the dynamic-mechanical response of the networks in both the anisotropic and isotropic states. Values of the storage and loss dynamic moduli in the range 10⁶-10⁷ Pa were detected in the isotropic state. Above the α relaxation temperature, either an elasticity or viscosity dominant state was observed depending upon the crosslink density of the network.