Copolymerization of 2-Hydroxyethyl Acrylate and 2-Methoxyethyl Acrylate via RAFT: Kinetics and Thermoresponsive Properties

Abstract

Kinetic studies of the (co)polymerization of 2-hydroxyethyl acrylate (HEA) and/or 2-methoxyethyl acrylate (MEA) via reversible addition-fragmentation chain transfer polymerization (RAFT), using dibenzyltrithiocarbonate (DBTTC) as chain-transfer agent, resulting in well-defined copolymers, are presented. Both monomers were found to have equal reactivity revealing the formation of ideal random (azeotropic) copolymers. The thermoresponsive properties of aqueous solutions of the copolymers at 5 mg/ mL, depending on the polymer composition, the chain length, and the end-groups, were investigated. The cloud point (CP) of the synthesized copolymers increases with the content of HEA and decreases with the decreasing chain length. Exchanging one of the hydrophobic benzylic end-groups of the copolymers by isobutyronitrile resulted in more hydrophilic copolymers with significantly higher CP-temperatures. Thus, new potential biomaterials with an adjustable cloud point between 0 and 60 °C, showing a small hysteresis between heating and cooling, were successfully prepared.

Polymer-protein conjugation via a ‘grafting to’ approach – a comparative study of the performance of protein-reactive RAFT chain transfer agents

“…backbiting), 50 we have chosen work conditions that have been reported in literature to provide good control over the polymerization. 51,52 This will also be confirmed by our kinetic data, vide infra. Samples were analyzed by gas chromatography (GC) for monomer conversion and by size exclusion chromatography (SEC) for their molecular weight and dispersity.…”

NMR investigation of effect of dissolved salts on the thermoresponsive behavior of oligo(ethylene glycol)-methacrylate-based polymers

“…The semi-logarithmic plot of ln([M] 0 /[M] t ) versus reaction time was close to linear, indicating the polymerizations followed pseudo-first-order kinetics and exhibited constant free radical concentration without significant termination reactions. 41,42 The higher reactivity of OEGMA(475) compared with OEGMA(300) was surprising, and in the absence of reduced termination effects for the higher molar mass monomer (not expected for RAFT) cannot be readily explained. Similar observations were reported by Pietsch et al 43 who likewise could not attribute the differences in reactivity.…”

Synthesis of double hydrophilic poly(ethylene oxide)‐b‐poly(2‐hydroxyethyl acrylate) by single‐electron transfer–living radical polymerization

“…Other teams reported the controlled synthesis of HEA by RAFT using poly( N ‐isopropylacrylamide) (PNIPAM),6 poly (vinylidene chloride‐ co ‐methyl acrylate),7 or bovine serum albumin8 macro‐RAFT agents. HEA could also be copolymerized, by RAFT, with methyl acrylate (MA),9 ethyl acrylate,10 or 2‐methoxyethyl acrylate 11…”