Liquid Crystallinity of Thermotropic Para-Type Homo- and Copolyurethanes Containing Biphenylene Mesogen and Their Blends

Abstract

High-molecular-weight para-type homopolyurethanes prepared by polyaddition of 2,5-tolylene diisocyanate with 4,4‘-bis(ω-hydroxyalkoxy)biphenyls showed monotropic liquid crystallinity, when measurements were performed under shearing. For example, a polyurethane PU6T having [η] 0.82 which was obtained from 4,4‘-bis(6-hydroxyhexyloxy)biphenyl showed T I - LC of 201 °C and T LC - K of 181 °C. In addition, thermotropic liquid-crystalline para-type copolyurethanes PUmnT (m and n denoting carbon number in alkylene moiety: 2, 6, 8, and 11) were synthesized by polyaddition of the diisocyanate with two 4,4‘-bis(ω-hydroxyalkoxy)biphenyls having different alkylene lengths. For example, PU68T(75/25) had T I - LC of 188 °C and T LC - K of 173 °C. Blends of two para-type homopolyurethanes also exhibited monotropic liquid crystallinity. The liquid crystallinity was examined by differential scanning calorimetry measurement, polarized optical microscope observation, and X-ray diffractometry.

Microwave-assisted synthesis of isosorbide-derived diols for the preparation of thermally stable thermoplastic polyurethane

“…However, intrinsic viscosity [ η ] of PU(HDI)BPA , PU(HDI)THIO, PU(MDI)BPA and PU(MDI)THIO has been measured at 25 °C using a mixture of phenol and tetrachloroethane and the results are reported in Table 6 . The results obtained were in good agreement with those reported by Kayalvizhi et al [ 45 ] and Lee et al [ 46 ] for polyurethane polymers using the same solvent, therefore indicating the formation of polyurethane with medium-to-high molecular weights. Thermal properties of the synthesized polymers were investigated by differential scanning calorimetry (DSC) analysis with a heating rate of 10 °C/min.…”

Synthesis and properties of new liquid crystalline polyurethanes containing mesogenic side chain

“…Conventionally, TLCPUs have been prepared by polymerization of mesogen-containing monomers, i.e. a mesogenic diisocyanate with an aliphatic diol [15] or a mesogenic diol with an aliphatic or aromatic diisocyanate [5,7,8,11,12,16,17]. Segmented liquid crystalline polyurethanes prepared from a polymeric diol, diisocyanate, and a mesogenic diol as a chain extender are being investigated with much interest.…”

Synthesis of Enantiotropic Liquid Crystal Copolyurethanes Containing Para- and Meta-Type Diisocyanate Units in the Backbone

“…We have been studying the synthesis of thermotropic para-type aromatic polyurethanes containing alkylene spacers. − The para-type polyurethanes had a tendency to readily crystallize both by mesogenic interactions and by the intermolecular hydrogen bondings. Thus, first, to examine the effects of the mesogenic interactions, para-type polyurethanes without any mesogen were prepared. , Those polyurethanes exhibited monotropic liquid crystallinity induced by the intermolecular hydrogen bondings alone.…”

“…Thus, first, to examine the effects of the mesogenic interactions, para-type polyurethanes without any mesogen were prepared. , Those polyurethanes exhibited monotropic liquid crystallinity induced by the intermolecular hydrogen bondings alone. Next, to decrease the intermolecular hydrogen bondings, para-type mesogen-containing copolyurethanes including two alkylene spacers with different lengths were synthesized . It was revealed that the copolyurethanes also showed the monotropic nature.…”