Synthesis and Thermotropic Properties of Polyurethanes Prepared from 2,5-Tolylene Diisocyanate and 2,6-Bis(ω-hydroxyalkoxy)naphthalenes

Abstract

ABSTRACT:A series of thermotropic polyurethanes containing no mesogenic unit were synthesized by polyaddition of a para-type diisocyanate such as 2,5-tolylene diisocyanate (2,5-TDI) with 2,6-bis(w-hydroxyalkoxy)naphthalenes (BHNm: HO(CH2)mOC10H 6 O(CH2)mOH; m is the carbon number in the hydroxyalkoxy group). Intrinsic viscosities of the polymers were in the range of 0.27---0.48 dL g-1 . The thermal properties of these polymers were studied by differential scanning calorimetry, thermogravimetric analysis, polarizing microscopy, and X-ray diffractometry. Polyurethane 2,5-TDI/BHNm's (m=5, 6, 8, 11) prepared from BHNm and 2,5-TDI having methyl substituent on the phenylene unit exhibited monotropic liquid crystallinity. For example, polyurethane 2,5-TDI/BHN8 with [IJ]=0.30 exhibited a mesophase from 139 to lll°C on cooling. However, in the series of polyurethanes prepared by polycondensation of 1,4-phenylene diisocyanate (1,4-PDI) with BHNm, no explicit mesomorphic behavior was observed by DSC measurement and polarizing microscopic observation.

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

“…In the copolyurethanes containing both meta and para units in random distribution, the decrease in regularity of distributions of the mesogenic units and urethane linkages in the polymer backbone must have caused the decrease in persistence length and effective axial ratio, resulting in the decrease in both mesogenic interactions and intermolecular hydrogen bondings. Thereby, an appropriate magnitude of the intermolecular interactions to cause the enantiotropic liquid crystallinity might be attained, because in the para-type polyurethanes containing biphenylene mesogen, strong intermolecular interactions readily caused the crystallization but not the liquid crystallization. − …”

“…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. Next, to decrease the intermolecular hydrogen bondings, para-type mesogen-containing copolyurethanes including two alkylene spacers with different lengths were synthesized .…”

Thermal and mesogenic properties of semirigid polyamides based on mono‐ or trimethylsubstituted 1,3‐diaminobenzenes

“…Uryu et a1. 21,22) also reported that semirigid polyurethanes composed of non-mesogenic units exhibit thermotropic LC properties due to intermolecular interaction via hydrogen bonding of urethane linkages. These results suggest that the amide or urethane linkage plays an important role in LC formation and the traditional biphenyl or diphenyl units are not always necessary to form LC phases when a certain interaction occurs between the polymer chains.…”

Preparation and thermotropic liquid crystalline properties of semirigid copolyurethanes composed of biphenyl units and partially fluorinated aliphatic chains

“…5 properties was discussed. [10][11][12][13][14][15][16][17] Some of them In the present paper, this reaction was applied showed unstable and/or ill-defined LC textures in to the synthesis of novel fluorine-containing therspite of the presence of the urethane linkage, motropic semirigid LC copolyurethanes from the which promotes LC formation via intermolecular monomers 1 and 2a,b and alkylene diphenyl dihydrogen bonding, 10-14 in the backbone. The incarbamates 3a-i (Scheme 1).…”