Characterization and Thermal Behaviour of Polymer-Dispersed Liquid Crystals
The thermal behaviour of polymer dispersed liquid crystals (PDLC), blends of poly(ethylene-co-methylacrylic acid) (PEMA) with 4-(n-hydroxypropoylxy)-4'-cyanobiphenyl (H3CB) prepared by solvent-induced phase separation (SIPS) method, has been characterized using differential scanning calorimetry (DSC) and polarized light microscopy (POM). Study shows that the concentration of the mixture of PEMA/ H3CB must be least 30%, which will exhibit nematic to isotropic transition phase during heating or cooling. Above 30 wt % 3CB the mixtures exhibited nematic phase, and this was detected as a splitting of the nematic-isotropic peak in the DSC thermograms. The clearing temperature of the PEMA/H3CB mixtures was higher than that of pure H3CB’s, the average increasing being 14°C, which is the evident that the polymer matrix could stable the nematic phase. This behaviour is in contrast with other reports about polymer-dispersed liquid crystals. In addition, thermal decomposition was also studied by thermogravimetry in nitrogen environments. A double-stage decomposition process was found in nitrogen atmosphere, and this was mainly due to H3CB for the first step and the PEMA decomposition for the second step.
Zhengyi Jiang, Jingtao Han and Xianghua Liu
X. G. Han et al., "Characterization and Thermal Behaviour of Polymer-Dispersed Liquid Crystals", Advanced Materials Research, Vols. 152-153, pp. 284-287, 2011