Synthesis of Well-Defined Alternating Copolymers by Controlled/Living Radical Polymerization in the Presence of Lewis Acids

Abstract

Several controlled/living radical polymerization (CRP) techniques (atom transfer radical polymerization (ATRP), nitroxide-mediated polymerization (NMP), iodide degenerative transfer polymerization (IDTP), and reversible addition-fragmentation transfer polymerization (RAFT)) were studied for the alternating copolymerization of a donor monomer (styrene) and an acceptor monomer (methyl methacrylate or methyl acrylate) complexed with Lewis acid. RAFT polymerization was found to be the most versatile system. The combination of RAFT and Lewis acids complexation techniques allows synthesis of well-defined alternating copolymers poly(styrene-alt-methyl methacrylate) with controlled molecular weight (up to M n ) 70 000 g mol -1 ), low polydispersities (Mw/Mn < 1.3), and controlled comonomer sequences (∼90% of alternating triads). These results were obtained in the presence of diethylaluminum chloride and ethylaluminum sesquichloride. Moreover, the alternating copolymers obtained in such copolymerizations retain chain end functionality and were used as macroinitiators for the synthesis of well-defined diblock copolymers poly(methyl methacrylate-alt-styrene)-b-polystyrene.

Living Radical Polymerization by the RAFT Process

“…RAFT polymerization can be conducted in the presence of Lewis acids.There are reports of attempted tacticity control of homopolymers [91,[168][169][170] (to enable the synthesis of stereoblock copolymers [171] ) and control of the alternating tendency for copolymerizations [172,173] through the use of Lewis acids as additives. For MMA polymerization, the addition of the Lewis acid scandium triflate, Sc(OTf) 3 , increases the fraction of isotactic triads and enhances the rate of polymerization in conventional radical [174] and RAFT processes.…”

Tailored Polymer Microstructures Prepared by Atom Transfer Radical Copolymerization of Styrene and N‐substituted Maleimides

“…[56][57][58][59][60] Hence, shortly after their discoveries, these methods have been investigated for synthesizing well-defined copolymers such as statistical, gradient or alternating copolymers. [23,[61][62][63][64] In the latter case, the copolymerization of styrene with strong electron acceptors such as MAh or MIs was reported. For instance, the first example of nitroxide mediated alternating copolymerization of styrene and N-butyl maleimide was published by Lokaj and co-workers in 1999.…”

Monomer Sequence Control via Living Anionic Copolymerization: Synthesis of Alternating, Statistical, and Telechelic Copolymers and Sequence Analysis by MALDI ToF Mass Spectrometry

“…17 This monomer combination was later exploited by Hawker 14 who used an excess of styrene with maleic anhydride to prepare a block copolymer of poly(styrene-co-maleic anhydride)-block-polystyrene by nitroxide-mediated radical polymerization. Lutz 15 expanded on this idea of exploiting a monomer incapable of homopolymerization, with sequential monomer addition to prepare a multi-block copolymer.…”

“…There are a number of reported examples of other alternating copolymers prepared by controlled free radical, [16][17][18][19] ROMP, 20 cationic, 21 and living anionic copolymerizations. [22][23][24][25][26][27] Of particular interest for living anionic copolymerizations is the monomer 1,1-diphenylethylene (DPE).…”