Controlling the Polymer Microstructure in Anionic Polymerization by Compartmentalization

Abstract

An ideal random anionic copolymerization is forced to produce gradient structures by physical separation of two monomers in emulsion compartments. One monomer (M) is preferably soluble in the droplets, while the other one (D) prefers the continuous phase of a DMSO-in-cyclohexane emulsion. The living anionic copolymerization of two activated aziridines is thus confined to the DMSO compartments as polymerization occurs selectively in the droplets. Dilution of the continuous phase adjusts the local concentration of monomer D in the droplets and thus the gradient of the resulting copolymer. The copolymerizations in emulsion are monitored by real-time H NMR kinetics, proving a change of the reactivity ratios of the two monomers upon dilution of the continuous phase from ideal random to adjustable gradients by simple dilution.

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

“…54 The comonomer pair TsDAz and TsMAz produce random copolymers in solution, but when separated from each other by an emulsion consisting of DMSO-droplets and cyclohexane as the continuous phase, variable gradients can be obtained by partitioning of both monomers, when the continuous phase is diluted. 136,143,149 This is represented in the apparent reactivity ratios, which are r app (TsMAz) = 4.98 and r app (TsDAz) = 0.20 in case of a 1 : 20-DMSO/cyclohexane emulsion, revealing the formation of strong gradient copolymers. [150][151][152]…”

“…The anionic ROP of sulfonyl aziridines is typically initiated by secondary N-sulfonamide-initiators, such as the alkali salts of N-benzyl-4-methylbenzenesulfonamide, 138 N-pyrene-methanesulfonamide, 124,132,136 or butyl lithium (Table 2). 143,144 Also a bifunctional initiator N,N′-(1,4-phenylenebis(methylene))dimethane-sulfonamide was introduced in 2017.…”

“…Copolymerizations of different sulfonyl aziridines give access to random or gradient copolymers, depending on the nature of the sulfonyl group. 136 The reactivity ratios of 2-methyl tosyl aziridine (TsMAz) and 2-decyl tosyl aziridine (TsDAz) were determined via real-time 1 H NMR spectroscopy and proven to be an ideal random copolymerization with r(TsMAz) = 1.08 and r(TsDAz) = 0.98 and r(TsMAz)•r(TsDAz) = 1.05. In contrast, combining monomers with different sulfonyl groups, resulted in (multi)gradient copolymers.…”

Computer‐Aided Living Polymerization Conducted under Continuous‐Flow Conditions†

“…In 2021 , the Chen group developed a computer‐aided droplet‐ flow platform based on PET‐RAFT polymerization, enabling the programmable preparation of gradient copolymers of tunable gradient tendency, low dispersity and good chain‐end fidelity (Figure 7). [ 50 ] Different from any previous methods used to synthesize gradient copolymers ( e.g ., concurrent tandem RDRP of methacrylates reported by Sawamoto, [ 81 ] the living ionic emulsion polymerization of activated aziridines reported by Wurm [ 82 ] ), this droplet‐flow approach utilized different solubilities of monomers in droplets and carrier phase to generate the gradient sequence during monomer diffusion and chain‐growth for the first time. It circumvented the existing reactivity limitation in living gradient copolymerization, allowing the transformation of various monomers including both hydrophobic and hydrophilic acrylates/acrylamides.…”

Ultrafast organocatalytic ring‐opening polymerization of N‐sulfonyl aziridine in the melt

“…[20][21][22] Although this anionic polymerization was first reported in 2005 by Toste and Bergman, 23 it was ignored for about 10 years and revived by Wurm, Carlotti, Taton et al in recent years with significant progress have been achieved. [24][25][26][27][28][29][30][31][32] For instance, various kinds of N-sulfonyl aziridine monomers with different substituents, such as N-ferrocenylsulfonyl-2-methylaziridine, 25 and acetalprotected aziridine, 27 have been synthesized and used in this anionic ROP. Moreover, N-(sulfonyl)azetidines have been used to produce linear poly(trimethylenimine)s and polysulfonamides by Rupar et al [33][34][35][36] Commonly, the ROP of N-sulfonyl aziridines was performed in dry DMF at elevated temperature initiated by N-benzyl sulfonamide/potassium hexamethyldisilazide (KHMDS).…”