Photocleavable and tunable thermoresponsive amphiphilic random copolymer: Self‐assembly into micelles, dye encapsulation, and triggered release

Abstract

ABSTRACT A double‐responsive amphiphilic random copolymer (P(OEtOxA)‐ ran ‐PNBA) composed of thermoresponsive poly(oligo(2‐ethyl‐2‐oxazoline)acrylate) (P(OEtOxA)) segments and photocleavable poly(2‐nitrobenzyl acrylate) (PNBA) segments is synthesized via combination of cationic ring‐opening polymerization (CROP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization techniques. The P(OEtOxA)‐ ran ‐PNBA copolymer exhibits lower critical solution (LCST)‐type soluble‐to‐turbid phase transition in water with tunable cloud point ( T cp ) with respect to chain length of P(OEtOxA) segment present. The photocleavage of PNBA segments by UV irradiation transforms amphiphilic P(OEtOxA)‐ ran ‐PNBA to fully hydrophilic P(OEtOxA)‐ ran ‐poly(acrylic acid) resulting in the appreciable increase of T cp of copolymer in aqueous solution. Owing to the amphiphilic nature, the P(OEtOxA)‐ ran ‐PNBA copolymer molecules self‐assemble into well‐dispersed spherical micelles in water. There is a disruption of the copolymer micelles with UV light irradiation as well as shrinkage of micellar size with increasing temperature above the LCST of copolymer in solution. Finally, the encapsulation of hydrophobic guest molecule (nile red) into P(OEtOxA)‐ ran‐ PNBA copolymer micelles and thermo‐ and photo‐triggered release of nile red are demonstrated. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55 , 1714–1729