Designing catechol‐end functionalized poly(DMAm‐co‐NIPAM) by RAFT with tunable LCSTs. Issue 24 (15th October 2017)

• Record Type: Journal Article
• Authors: Oyeneye, Olabode O.; Xu, William Z.; Charpentier, Paul A.
• Is Part Of: Journal of polymer science. Volume 55:Issue 24(2017)
• Page Start: 4062
• Page End: 4070
• Publication Date: 2017-10-15
• Subjects: catechol -- kinetics -- lower critical solution temperature -- RAFT; 547
• DOI: 10.1002/pola.28879
• Languages: English
• ISSNs: 0887-624X

Abstract

ABSTRACT: Providing catechol‐end functionality to controlled structure lower critical solution temperature (LCST) copolymers is attractive, given the versatility of catechol chemistry for tethering to nanostructures. Controlled polymer chain lengths with catechol RAFT end groups are of interest to provide tunable LCST behavior to nanoparticles, although these polymerizations are relatively unexplored. Herein, the reactivity ratios for the RAFT copolymerization of N, N ‐dimethylacrylamide (DMAm) and N ‐isopropylacrylamide (NIPAM) pairs based on catechol‐end RAFT agents using an in situ NMR technique were first determined. Several catechol‐end poly(DMAm‐ co ‐NIPAM) samples were then prepared using the RAFT agent to provide copolymer. The reactivity ratios for the DMAm‐NIPAM pair were r DMAm = 1.28–1.31 and r NIPAM = 0.48–0.51. All the poly(DMAm‐ co ‐NIPAM) samples were found to have M n values ≤ 26 kDa and Ð < 1.08 with LCST values ranging from 31 to 92°C, while maintaining a short range of glass transition temperature ( T g = 118–137°C). The difference in LCST values for the catechol functionalized poly(DMAm‐ co ‐NIPAM) based on 0.5 wt% aqueous buffered solutions at pH 5.5 and 8.5 was found to be <3.0°C. These conditions are suitable for subsequent catechol‐induced coordination and nucleophilic addition chemistry for covalent and noncovalent linkages during subsequent post‐modification. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem.2017, 55, 4062–4070 Abstract : A series of low dispersity catechol‐end functionalized thermoresponsive copolymers (dimethylacrylamide and n‐isopropylacrylamide pairs) were designed based on RAFT chemistry to possess varying lower critical solution temperature (LCST) values. The copolymers exhibited excellent thermoresponsive behaviors which are reasonably stable in conditions necessary for the postpolymerization modifications of the catechol and trithiocarbonate functionalities.