Cycloolefin Copolymer Analogues from Styrene and Isoprene: Cationic Cyclization of the Random Copolymers Prepared by Living Anionic Polymerization

Abstract

This paper reports a novel and practical method for the synthesis of styrene-isoprene-derived cycloolefin copolymer analogues via the intramolecular Friedel−Crafts alkylation of well-defined random copolymers of styrene and isoprene prepared by living anionic copolymerization in the presence of a small amount of tetrahydrofuran as a randomizer. The random copolymers with an almost equimolar amount of the two monomers (styrene:isoprene = 48:52) and a predominant 1,4-isoprene-enchainment (1,4-:1,2-:3,4- = 67:1:32) were intramolecularly cyclized with CF3SO3H efficiently to give the soluble cycloolefin copolymer analogues with a high glass transition temperature (T g). The T g increased dramatically (T g = 20 vs 130 °C) on cyclization between the aromatic ring of the styrene unit and the adjacent CC bond in the isoprene unit via the intramolecular Friedel−Crafts alkylation that results in the tetrahydronaphtyl bicyclic unit in the backbone chain, for which the highest T g was observed at the equimolar content of isoprene and styrene. The predominant Friedel−Crafts cyclization between the styrene and the adjacent isoprene units was supported by the model reactions of the corresponding low molecular weight model compounds.

Dynamically cured polypropylene/Novolac blends compatibilized with maleic anhydride‐g‐polypropylene

“…As discussed in the previous papers,13, 14 the cyclization took place predominantly between the CC double bonds of the isoprene unit and phenyl groups of the adjacent styrene unit, that is, Friedel‐Crafts cyclialkylation. However, the consumption of CC was not quantitative in principle due to the existence of consecutive isoprene‐isoprene units, which inevitably form during random copolymerization.…”

“…1). As in previous papers,13, 14 r ‐SIR was first synthesized with sec ‐butyllithium as the initiator in cyclohexane at 40 °C. To make the monomer sequence random and less blocky, the premixed 1:1 mixture of styrene and isoprene was incrementally and continuously added to the reaction solution throughout the reaction in the presence of a small amount of THF as the randomizer.…”

“…The cyclized r ‐SIRs were obtained by the cyclization of anionically synthesized r ‐SIR as described in our previous publication 13, 14. A typical example for r ‐SIR polymerization is given below.…”

“…More recently, we reported the synthesis of cycloolefin copolymer analogues through the anionic random copolymerization of styrene (St) and isoprene (Ip) in the presence of tetrahydrofuran (THF) as a randomizer with subsequent intramolecular Friedel‐Crafts alkylation between the aromatic ring of the styrene unit and the adjacent double bond in the isoprene unit (Scheme ) 13, 14. Because of the predominantly formed tetrahydronaphthyl bicyclic unit in their backbone, these polymers possess glass transition temperatures ( T g ) of approximately 130 °C, higher than those of polyisoprene and polystyrene.…”

Extremely High Glass Transition Temperature Hydrocarbon Polymers Prepared through Cationic Cyclization of Highly 3,4‐Regulated Poly(Phenyl‐1,3‐Butadiene)

“…Increasing efforts have been made to prepare high‐temperature hydrocarbon polymers in recent years. These strategies have involved: 1) the enhancement of the tacticity of the polymer chain, 2) the incorporation of bulky pendant groups in the side chain, and 3) the introduction of cyclic structures in the main chain . However, the fabrication of hydrocarbon polymers with high service temperature (Tg > 250 °C) remains a challenge.…”