Microwave‐Assisted Reversible Addition–Fragmentation Chain Transfer Polymerization of Cationic Monomers in Mixed Aqueous Solvents

Abstract

Cationic polymers are an interesting class of macromolecules due to their versatility and emerging properties that can be used for various industrial and biomedical purposes. This report is focused on investigating the use of microwave heating in the reversible addition–fragmentation chain transfer polymerization of functional cationic monomers, N‐(3‐aminopropyl)methacrylamide hydrochloride (APMA) and N‐[3‐(dimethylamino)propyl]methacrylamide (DMAPMA). Under comparable polymerization reaction conditions, the microwave‐assisted reaction achieves up to 270% (APMA) and 375% (DMAPMA) rate enhancement over conventional oil‐bath mediated set‐up. Linear relationships are observed between number average molecular weight and monomer conversion for different target degrees of polymerization to give low‐ to high‐molecular‐weight cationic polymers. Chain extension experiments show increase in molecular weight of the cationic polymers with narrow dispersities (Ð < 1.2) indicating retention of the chain transfer agent with no observable aminolysis or hydrolysis during polymerization.

Role of External Field in Polymerization: Mechanism and Kinetics

“…1049 Schellinger and co-workers applied microwave heating to the RAFT polymerization of cationic monomers (i.e., N-(3-aminopropyl) methacrylamide hydrochloride and N-[3-(dimethylamino)propyl] methacrylamide). 1050 As expected, great improvement of production efficiency, narrowly dispersed polymers, and sound end group functionalities allowing effective chain extension were gained in all cases. Similar to heterogeneous FRP systems, RAFT precipitation polymerization and RAFT dispersion polymerization were conducted under microwave irradiation.…”

“…Also, the same group synthesized a well-defined vinyl ester containing homopolymer and block copolymers by RAFT/MADIX polymerization under microwave irradiation . Schellinger and co-workers applied microwave heating to the RAFT polymerization of cationic monomers (i.e., N -(3-aminopropyl) methacrylamide hydrochloride and N -[3-(dimethylamino)­propyl] methacrylamide) . As expected, great improvement of production efficiency, narrowly dispersed polymers, and sound end group functionalities allowing effective chain extension were gained in all cases.…”

Polymer Processing under Microwaves

“…These drawbacks are avoided by using microwave heating; the same feature is revealed in the case of chemical reactions in solution, where the reactional medium is more efficiently heated thanks to microwaves and the reaction proceeds uniformly throughout the heated system, reaching completion simultaneously in the whole reactional volume [32]. In addition, microwave-assisted polymer synthesis, and overall reactions in organic chemistry, provides products with higher purities and reduces side reactions, both in solution and bulk [33][34][35][36].…”