Reversible Addition−Fragmentation Chain Transfer (RAFT) Polymerization in an Inverse Microemulsion System: Homopolymerization, Chain Extension, and Block Copolymerization†Paper no. 140 in a series on Water-Soluble Polymers.

Abstract

We report the first successful reversible addition-fragmentation chain transfer inverse microemulsion polymerization (RAFT-IMEP). The inverse microemulsion (IME) system conditions were optimized by generating pseudo-three-component phase diagrams. The IME consisted of the hydrophilic monomer N,N-dimethylacrylamide (DMA), water, hexanes, nonionic surfactants, and a cosurfactant. The polymerization kinetics and the living character of RAFT-IMEP, conducted with varying amounts of dispersed aqueous phase, were similar to that observed for aqueous RAFT polymerization of DMA. The colloidal stability during polymerization was also investigated via dynamic light scattering. Decreasing the weight fraction of the dispersed aqueous phase leads to an increase in colloidal stability and a decrease in microemulsion size. An increase in the dispersity of molecular weight is also observed with a decrease in the weight fraction of dispersed aqueous phase. This observation is attributed to uncontrolled polymer that forms during the early stages of RAFT-IMEP. Chain extension or block copolymer formation is accomplished by simple addition of DMA or DEA to the polyDMA macroCTA, demonstrating the potential utility for preparing doubly hydrophilic block copolymers under appropriate RAFT/IMEP conditions. † Paper no. 140 in a series on Water-Soluble Polymers.

Living Radical Polymerization by the RAFT Process – A Third Update

“…[326,570] The process has been performed with a series of trithiocarbonate RAFT agents. [326] The relative efficacy of these was attributed to the partition coefficient between the aqueous and oil phase.…”

RAFT Inverse Microemulsion Polymerization: Effects of Monomer Solubility and Different Types of Initiators

“…Microemulsion formulations, both direct and inverse systems, are generally achieved by exploring a pseudo‐three‐component phase diagram, composed by the main components of a microemulsion: surfactant(s), oils, and water‐soluble compounds. In most cases, high amounts of surfactants are necessary (>10 wt%) to generate a thermodynamic stable microemulsion . Different recipes were tested using a nonionic surfactant (PEO 6 C 18 ; HLB 8), cyclohexane as principal oil component, and aqueous solutions containing DMAEMA with distinct pH values adjusted with acidic acid (see Table S1 in the Supporting Information).…”

“…However, despite the RAFT process being well established, little attention has been given to this technique in an inverse microemulsion system. In fact, only two works have been published to date, both using N,N ‐dimethylacrylamide as monomer …”

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

“…higher Đ) than ab initio, although absolute comparison of blocking efficiency in different studies is difficult. The potential of microemulsion polymerisation has yet to be fully realised for solvophobic block copolymer syntheses, although the few published examples suggests that highly pure products can be obtained, 97,118 which may be a direct result of confinement effects, where termination and radical side reactions are suppressed. 154,155 Methods in which the monomer is initially soluble and the growing polymer precipitates can further simplify the polymerisation process i.e.…”