The influence of the 8OCB liquid crystal concentrations on the ST-AA photonic crystal synthesis

Abstract

This study presents the synthesis of polymer dispersed liquid crystals (PDLCs) composed of polymer particles and 4′-octyloxy-4-cyanobiphenyl (8OCB) liquid crystal. The motivation of this study resides in the great application prospects in widespread advanced technique fields for the obtained polymer-8OCB colloids and the possibility to implement the synthesis method for other types of LCs. The synthesis procedure involved soap-free emulsion polymerization in the presence of liquid crystal. This preliminary study describes for the first time the synthesis of nearly monodisperse PDLC polymer particles, as evidenced by SEM and DLS. The particles do not have the capacity to self-assemble. This study highlights the mechanism of generating PDLC particles, where 8OCB favors the chain transfer reactions and acts as a plasticizer between the polymer chains. These aspects were ascertained using GPC, DSC, SEM and EDX analysis. Increasing the 8OCB concentration in the system leads to lower molecular weights. The particle size was proportional to the amount of 8OCB. The limitations of the present synthesis approach are the reduced solubility of 8OCB in the monomer mixture. In consequence, a certain limit of LC concentration in the polymer matrix cannot be surpassed.