Cationic Copolymerization of Styrene Derivatives and Oxiranes via Concurrent Vinyl-Addition and Ring-Opening Mechanisms: Multiblock Copolymer Formation via Occasional Crossover Reactions

Abstract

Styrene derivatives were demonstrated to cationically copolymerize with 2,2-disubstituted oxiranes, which can generate a tertiary carbocation by the ring opening of the oxonium ion, through crossover reactions. The copolymerization proceeded with comparable consumptions of both the vinyl and cyclic monomers when appropriate combinations, such as p-methoxystyrene and 2-ethylhexyl β-methylglycidyl ether or p-methylstyrene and β-methylepichlorohydrin, in terms of reactivity were used. The homopropagation reactions of both monomers occur preferentially compared to the crossover reactions, which resulted in multiblock copolymers with relatively long blocks. The oxirane-derived carbocation caused both Friedel−Crafts reactions with a styrene derivative and β-proton elimination as chain transfer reactions. For the analysis of the copolymer structures, unlike the acetal structure resulting from the crossover from a vinyl ether to an oxirane, the sec-benzylic ether structure derived from the crossover from a styrene derivative to an oxirane was difficult to detect by 1 H NMR spectroscopy due to overlap with the peaks of the oxirane units in the main chain. However, the occurrence of crossover reactions was confirmed by 13 C NMR analysis by comparison with the spectra of model polymers. Acidolysis of the sec-benzylic ether structure by trifluoroacetic acid also facilitated the determination of the copolymer structure.

RAFT step-growth polymerization via the Z-group approach and deconstruction by RAFT interchange

“…The C-C single bonds in vinyl polymers offer excellent stability for the intended applications, yet these polyethylene-like polymers are notoriously difficult to degrade, posing grand challenges in recycling these polymers and when degradation is desirable (e.g., drug delivery). [1][2][3] Various strategies have been developed to overcome this challenge, including copolymerization with degradable monomers, [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] introduction of degradable groups by combining with step-growth polymerization, [19][20][21][22][23][24] depolymerization to monomers under special conditions, [25][26][27][28][29][30][31] and degradation to oligomers catalyzed by special reactions. [32][33][34][35] Among them, introducing labile carbon-heteroatom bonds (e.g., ester) into vinyl polymers via copolymerization of a second monomer containing such labile bonds is one of the most efficient methods.…”

Anionic Hybrid Copolymerization of Cyclic and Vinyl Monomers without Transesterification

“…[10][11][12][13] In 2013, Aoshima and co-workers reported the cationic hybrid copolymerization (CHcP) of vinyl ether (VE) and alkylene oxide. [14][15][16][17][18] The rational design of monomer structures and initiation systems is the key to realize the crossover between cationic vinyl-addition polymerization of vinyl ether and cationic ring opening polymerization of alkylene oxide. Recently, You et al reported a radical/anionic hybrid copolymerization (RAHcP) by employing trithiocarbonate as both a chain transfer agent for radical reversible addition-fragmentation chain transfer polymerization of vinyl monomers and an initiator of ROP simultaneously.…”

“…[ 10–13 ] In 2013, Aoshima and co‐workers reported the cationic hybrid copolymerization (CH c P) of vinyl ether (VE) and alkylene oxide. [ 14–18 ] The rational design of monomer structures and initiation systems is the key to realize the crossover between cationic vinyl‐addition polymerization of vinyl ether and cationic ring opening polymerization of alkylene oxide. Recently, You et al.…”

Synthesis and Degradation of Vinyl Polymers with Evenly Distributed Thioacetal Bonds in Main Chains: Cationic DT Copolymerization of Vinyl Ethers and Cyclic Thioacetals

“…Among them, copolymerization of heteroatom‐containing cyclic monomers with common vinyl monomers, by which labile carbon‐heteroatom bonds can be introduced via ring opening of the cyclic structures, is one of the most efficient methods [23–26] . Various cyclic compounds, which are copolymerizable via ring‐opening reactions, have been developed to date and include cyclic ketene acetals, [27–40] thionolactones, [41–47] and cyclic allylic sulfur compounds [48–52] for radical polymerization as well as oxiranes, [53, 54] cyclic acetals, [55, 56] hemiacetal esters, [57] and 1,3‐dioxa‐2‐silacycloalkanes [58] for cationic polymerization.…”