RAFT polymerization in supercritical carbon dioxide based on an induced precipitation approach: Synthesis of 2-ethoxyethyl methacrylate/acrylamide block copolymers

Abstract

A new controlled/living heterogeneous polymerization technique using RAFT in benign supercritical CO2 is described involving the formation of monomer‐swollen seed particles by precipitation of macroRAFT agent prior to polymerization. Controlled/living character of the induced precipitation is compared with the equivalent solution polymerization. The large scale synthesis of poly(2‐ethoxyethyl methacrylate)‐b‐poly(acrylamides) useful for biomedical applications is made possible with the polymer isolated as powders at high conversions, thus circumventing the requirement for volatile organic solvents. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2351–2356

Block copolymer synthesis by controlled/living radical polymerisation in heterogeneous systems

“…Hawkins et al exploited scCO 2 in a precipitation polymerisation during the second step of block copolymer synthesis. 121 DTB-functional poly(2-ethoxyethyl methacrylate) (PEEMA) was first prepared in solution then dissolved in monomer (DMA or 4-acrylomorpholine, 4AM). CO 2 was added and the mixture heated into the supercritical state, upon which the monomer swollen macro-RAFT particles precipitated from solution and polymerisation began.…”

“…precipitation polymerisation), since these additional components are difficult to separate and could be degrading to bulk or surface properties of the polymer. However, there are relatively few examples of successful CLRP block copolymer syntheses in precipitation polymerisations, 101,121,124 probably due to challenges in controlling reagent partitioning and particle aggregation.…”

Synthesis of two-phase polymer particles in supercritical carbon dioxide

“…The three most widely used reversible-deactivation radical polymerisation (RDRP) techniques; nitroxide-mediated radical polymerisation (NMP), atom transfer radical polymerisation (ATRP) and reversible addition-fragmentation chain transfer polymerisation (RAFT), have all been used to synthesise well-defined particles with narrow size distributions. [12][13][14][15][16] These techniques can give access to more complex structures including cross-linking, 17 incorporation of metal nanoparticles, 18 and more recently block copolymer particles with internal phase separation. [19][20][21] Particles with phase-separated internal morphologies are usually synthesised via emulsion-based techniques, typically with size between 60-700 nm.…”