Monomer Sequence Regulation in Main and Side Chains of Vinyl Copolymers: Synthesis of Vinyl Oligomonomers via Sequential Atom Transfer Radical Addition and Their Alternating Radical Copolymerization

Abstract

We propose a novel strategy of monomer sequence regulation in main and side chains of vinyl copolymers using sequential atom transfer radical addition (ATRA) for maleimide-ended sequence-regulated vinyl "oligomonomers" and their alternating radical copolymerization with styrene. To establish this strategy, a series of sequence-regulated vinyl oligomers were prepared by the ATRA of styrene (S) or methyl acrylate (A) to a halide-possessing A or S unit (methyl α-bromopropionate or 1-phenylethylhalide). The obtained halide-ended sequence-regulated vinyl oligomers were converted into maleimide-ended oligomonomers by S N 2 reaction with the potassium salt of furan-protected maleimide (M) followed by deprotection. The maleimide-ended oligomonomers were then radically copolymerized with styrene in an alternating fashion to result in sequence-regulated vinyl copolymers consisting of a controlled monomer sequence (SA, AS, AA, and SS) in the side chain and an alternating sequence (MS) in the main chain. The solubility of the copolymers depended on not only the monomer composition but also the sequence of the side chains, whereas the thermal properties were negligibly affected by the side-chain monomer sequences.

Sequence-regulated vinyl copolymers with acid and base monomer units via atom transfer radical addition and alternating radical copolymerization

“…As we reported previously, the slightly lower molecular weights may be due to the compact hydrodynamic volume of the copolymers with pendent side chains compared to that of polystyrenes as standard samples for the molecular weight calibration. 17,18 These results indicate that a series of main-and sidechain sequence-regulated vinyl copolymers with an acid or base function and nearly the same controlled chain lengths (DP n ~ 100) were successfully synthesized.…”

“…For the radical copolymerization of styrene and oligomonomers with a t-butyl acrylate unit (M-SA p , M-A p S) at a 1:1 feed ratio in toluene at 60 °C with AIBN, both styrene and maleimide group were consumed at nearly the same rate to yield copolymers with relatively high molecular weights (M n > 180000) similar to the previously reported unfunctionalized maleimide-ended oligomonomers and styrene. 17,18 However, radical copolymerization of the aminefunctionalized oligomonomers with styrene resulted in only low molecular weight polymers (M n = 1000-2000) in toluene and DMF at 60 °C due to irreversible chain-transfer reactions caused by the amine moiety despite their consumption at nearly the same rate. However, in a fluorinated alcohol (PhC(CF 3 ) 2 OH) with weak acidity, the alternating radical copolymerization successfully proceeded at 20 ºC with a low temperature radical azo-initiator (V-70), resulting in alternating copolymers with higher molecular weights (M n = 20000-40000).…”

“…Many approaches for controlling the monomer sequences in vinyl copolymers have been reported including copolymerization with highly selective propagation, such as alternating copolymerization, [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] template polymerization, 21-31 sequential multi block copolymerization, [32][33][34][35][36][37][38] iterative single monomer addition reactions, [16][17][18][39][40][41][42][43][44][45][46] and other polymerizations of designed monomers. 39,41,[46][47][48][49][50][51][52][53][54][55][56][57][58] However, the degree of controllability, number of controllable sequence units, and molecular weigh...…”

Upscaling single unit monomer insertion to synthesize discrete oligomers

“…Motivated by the desire to prepare such precise structures, an increasing number of innovative physical and chemical approaches have been developed during the past decades, including automated separation system, atom transfer radical addition, click‐based chemistry (thio‐ene, thio‐maleimide, and thiolactone), phosphoramidite chemistry, multicomponent reaction, photo‐ligation chemistry, and ionic polymerization techniques . Most of the elegant examples in these approaches use an iterative exponential growth (IEG) process, which evolves from step‐growth polymerization and uses pre‐protected bifunctional monomers to achieve sequential attachments and doubles the molecular weights of synthetic oligomers/polymers .…”

Sequence Determination and Regulation in the Living Anionic Copolymerization of Styrene and 1,1‐Diphenylethylene (DPE) Derivatives

“…Through controlled multiple monomer feeding procedures, the sequential distribution of alternating domains can be controlled. Based on this strategy, outstanding results in the synthesis of sequence‐controlled polymers have been gained mainly by means of the controlled radical polymerization (CRP) of styrene (St) and maleimide derivatives . During the living anionic polymerization (LAP), 1,1‐diphenylethylene (DPE) derivatives showed special characteristics in copolymerization.…”