Phase behavior of poly (ethylhexylacrylate)/E7 mixtures

Reactive blends of monofunctional 2-ethylhexyl acrylate monomer and the low molecular weight liquid crystal (LC) mixture E7 have been efficiently poly merized by a polymerization induced phase separation (PIPS) mechanism using UV radiation. An experimental phase diagram of the obtained Poly(ethylhexy lacrylate)/E7 blends has been investigated as a function of temperature and composition of the initial reactive mixtures. Polarized optical microscopy and DSC techniques were employed to determine the phase behavior. The obse rved temperature/composition phase diagram shows qualitatively an Upper Cri tical Solution Temperature (UCST) behavior. At LC concentrations below 50 w t%, a direct transition from the (nematic + isotropic)(N+I) to the isotropi c (I) phase is detected. From 50 to 90 wt% LC, there is clear evidence of t he existence of an (I+I) phase located between the (N+I) and the I phases. Above 90 wt% LC, the (I+I) phase is also expected but has not been observed experimentally.