Synthesis of mono/DI-[1-(2-anthryl)-1-phenylethylene] telechelic poly (methyl methacrylate), polystyrene, and polyisobutylene and related copolymerizations via photohemical reversible cycloaddition reactions

Abstract

The synthesis of novel 1-(2-anthryl)-1-phenylethylene (APE) di-telechelic polyisobutylenes were done by the utilization of a difunctional cationic initiator and the in situ addition of the non-homopolymerizable APE monomer to the chain ends. Mono and di-anthryl telechelic polystyrenes and anthryl telechelic poly(methyl methacrylate)s were also synthesized via living anionic polymerization by the incorporation of APE at initiation or at chain end. Products were characterized by 1H NMR spectroscopy and Size Exclusion Chromatography (SEC). The polymers were irradiated with 365 nm and 254 nm UV light and the reversible photocycloaddition of anthryl moieties was investigated. Irradiations at 365 nm were conducted to obtain chain extension of anthryl and di-anthryl telechelic polymers; initially for homopolymer solutions and then for polymer mixtures. The chain extension of di-anthryl telechelic PIBs through photocoupling at 365 nm produced higher molecular weight products from low molecular weight precursors. The effect of precursor polymer concentration on the degree of chain extension was investigated, and intermolecular interactions leading to the formation of tetramers was observed. Intramolecular interactions leading to formation of cyclic products was also observed in some extent during the chain extension process, especially in the low concentration conditions. The photocoupled products were UV irradiated at 254 nm, which yielded partial reversal of photocycloaddition of anthryl groups and consequent photoscission of polymers. Products obtained by UV irradiations of mixtures of di-anthryl telechelic polyisobutylenes and polystyrenes at 365 nm were cast into films and their thermal and mechanical properties were investigated.