Effects of hydroxylated acrylates on electro-optical performance and adhesion strength of polymer dispersed liquid crystal films

Abstract

In this study, effects of hydroxylated acrylate monomers that includes both monoacrylate and diacrylate on properties of the as-made polymer dispersed liquid crystal (PDLC) films are explored. The electro-optical response, microstructure and adhesion strength are characterized to compare the influences in detail. It is revealed that hydroxylated acrylate monomers can significantly enhance the adhesion strength in comparison with the non-hydroxylated monomer. Moreover, the hydroxyl group can alter the microstructure of the polymer matrix by affecting the polymerization and phase separation process. Thereby, the electro-optical response of the PDLC film is affected. Additionally, the influences are closely related to the position and concentration of hydroxyl group in acrylate monomers. When the hydroxyl group is located in the α-position or is distant from the reactive site, the improvement is limited. Increasing the concentration of hydroxyl groups by introducing monomers containing multiple hydroxyl groups in one molecule or combining hydroxylated monoacrylate and hydroxylated diacrylate monomers can change the microstructure type and deteriorate the electro-optical performance. By carefully balancing these factors, an optimized PDLC film can be obtained, whose adhesion strength is elevated to about 2.3 times that of the non-hydroxylated film and contrast ratio is improved from 135 to 262. This work is anticipated to provide deeper insights into the role of hydroxylated monomers and offer more possibilities to improve the overall performance of the PDLC films.