Synthesis and characterization of a hydrogen-bonded nematic network based on 4-propoxybenzoic acid side groups grafted onto a polysiloxane

• Published in: Liquid crystals Vol. 27; no. 2; pp. 169 - 176
• Main Authors: Xu, Hui, Kang, Ning, Xie, Ping, Zhang, Rong-Ben, Xu, Duan-Fu
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.02.2000
• ISSN: 0267-8292; 1366-5855
• DOI: 10.1080/026782900202930

A polymethylsiloxane with 4-propoxybenzoic acid side groups was prepared by hydrosilylation of polymethylhydrosiloxane and methyl 4-allyloxybenzoate followed by hydrolysis. The existence of strong hydrogen bonding interactions in this polymer due to dimerization of the carboxylic acid groups was demonstrated by FTIR. The polymer exhibits a nematic mesophase at elevated temperatures due to the self-assembly of hydrogen-bonded mesogens (dimers). After cooling from its nematic melt, a stable hydrogen-bonded nematic network structure was formed, as demonstrated by differential scanning calorimetry, polarizing optical microscopy, and X-ray diffraction. Temperature-variable FTIR analysis presents a convincing interpretation for the DSC thermogram of the polymer, and furthermore assists in understanding the process of formation of the nematic network and the reversibility of such hydrogen-bonded networks.