Functional polymers and sequential copolymers by phase transfer catalysis. XIX. Thermotropic polythioethers and copolythioethers based on 4,4′‐dithiolbiphenyl

Thermotropic liquid crystalline (LC) polythioethers and copolythioethers have been synthesized from 4,4′-dithiolbiphenyl (TB) and α,ω-dibromoalkanes having between two and twelve methylene units. Copolythioethers were prepared from TB and a 1:1 mol/mol ratio of 1,5-dibromopentane and α,ω-dibromoalkanes having nine to twelve methylene units. Peculiarities of the phase-transfer catalyzed (PTC) polyetherification reaction in the preparation of these polymers have led to aliphatic-ether structural units. This side reaction has been explained by a possible neighboring group effect with sulfur, through sulfonium formation, and is consistent with a mechanism previously proposed in PTC polyetherifications. While not significantly enhancing solubility, the copolymeric nature of these polymers have led to lower melting and isotropization temperatures with broad mesophase thermal stability ranges. Lastly, unique spherulitic textures resembling higher-ordered smectic mesophases have been observed in all the prepared polymers.