Thermal strain recovery of anelastic monodomain liquid crystalline networks: Mechanically induced strains ratios

A series of smectic liquid crystalline network polymers was subjected to a large uniaxial stress at temperatures far below the clearing temperature. Their dimensional recovery is anelastic showing substantial retained strain. This process produced a temporally stable monodomain state. Upon heating this monodomain from room temperature, recovery of the original film dimensions occurs. The strain recovery (length) curves show a pronounced curvature as the temperature approaches the smectic isotropic temperature. It is proposed that nanosegregation of netpoints in the smectic structure is responsible for the anelasticity and that the temperature dependence of the shape recovery is consistent with a balance between enthalpic and entropic forces with temperature. An interesting mechanically induced strains ratio (MISR) was observed on heating these prestressed films. Loss of the monodomain structure near the isotropization temperature is postulated to rationalize the shape of the MISR curves. [GRAPHICS] (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim