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

Abstract

Enantiotropic liquid crystal (LC) polyurethanes were synthesized for the first time. Thermotropic LC copolyurethanes PUnT(m/p)s (n, the number of methylene unit, 6, 8, and 11; m, metatype unit; p, para-type unit) were synthesized by polyaddition of 4,4′-bis(ω-hydroxyalkoxy)biphenyls (BPn) with two kinds of diisocyanates, that is, meta- type 2,4-and para-type 2,5-tolylene diisocyanates (2,4and 2,5-TDI). The liquid crystallinity was examined by differential scanning calorimetry (DSC), polarized optical microscopy, and X-ray diffractometry. All copolyurethanes consisting of PU6T(m/p)s and PU8T-(m/p)s with all m/p ratios showed liquid crystallinity in the cooling stage under shear. Of them, six PUnT(m/p)s (n ) 6 and 8; m/p ) 80/20, 60/40, and 50/50) showed enantiotropic liquid crystallinity on both heating and cooling stages. However, copolyurethane PU11T(m/p)s having the undecamethylene spacer did not exhibit any liquid crystallinity at the m/p ratio from 100/0 to 20/80, although PU11T(0/ 100) was monotropic. For example, a copolyurethane PU6T(80/20) exhibited enantiotropic liquid crystallinity in the temperature ranges from 156 to 164 °C on the heating stage and from 147 to 138 °C on the cooling stage.

Side-chain liquid crystalline polyacrylates containing 3,4-disubstituted pyrrole moiety

“…Below the glass transition temperature, the schlieren texture of SmC was maintained down to room temperature, and yet showed no evidence of fluidity to the shearing. 21 The transition temperatures for monomer 1 are summarized in addition to those for other monomers in Table I.…”

“…However, because the polymer melt in the liquid-crystalline state was very viscous, attempts to develop a characteristic schlieren texture by shearing 21 were unsuccessful. The other polymers also showed restricted fluidity in their liquid crystalline state.…”

Praseodymium/Polyureasulfone Complexes with Unusual Thermal, Luminescent and Magnetic Properties

“…Secondly, polyurea containing donor groups such as ÀNHÀ and ÀC¼O, has a good coordination ability to metal ions. [15][16][17][18][19] In particular sulfone-containing polyureas possess strong polar interactions between sulfone groups, which could lead to more stable framework, high packing density, small interchain distances, and high free volume. [20] Moreover, the incorporation of polar sulfone groups into benzenebased polymers could increase charge-conjugation symmetry, making the flow of electronic charges in the benzene-containing section easier.…”