Functional polydiynes prepared by metathesis cyclopolymerization of 1,7-dihalogen-1,6-heptadiyne derivatives

Abstract

We report the metathesis cyclopolymerization (MCP) of 1,7-dihalogen-1,6-heptadiyne derivatives by using MoCl₅/(n-Bu)₄Sn complex catalyst system. Five homopolymers (P1–P5) and a copolymer (P[1-co-5]) were obtained in high yields (up to 95%) with high molecular weights (M_w up to 210 000) under the optimized conditions (60 °C, 12 h, in 1,2-dichloroethane). The structures of the resultant polymers were characterized by FTIR, ¹H NMR, ¹³C NMR and UV-vis spectroscopic techniques, which confirmed the MCP methodology was successfully applied to the preparation of halogen-modified polydiynes. The resultant polydiynes possess good solubility in common organic solvents and high thermal stability. More significantly, these chloro-modified polydiynes demonstrated unprecedented upper critical solution temperature (UCST) behavior, which can be tentatively related to the halogen bonding between the halogen atoms and the oxygen/nitrogen atoms of solvents. The UCST performance of the polydiynes was influenced by the side chain of the polymers (58–110 °C) and copolymerization of different monomers (61–66 °C). Interestingly, by linking tetraphenylethene (TPE) groups onto the polymer side chains, the UCST process could be visually monitored due to the aggregation-induced emission characteristics of TPE groups.