Well defined and responsive amphiphilic block copolymers synthesized using TEMPO initiated thiol-ene reaction

Abstract

Well defined and responsive amphiphilic block copolymers based on poly(N-isopropyl acrylamide)-b-poly(isobornyl acrylate) (PNIPAM-b-PiBoA), poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) and poly(isobornyl acrylate)-b-poly(acrylic acid) (PiBoA-b-PAA) were synthesized using 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO) initiated thiol-ene reaction under ambient conditions. The preparation of two blocks for conjugation via TEMPO initiated thiol-ene reaction was carried out through Reversible Addition-Fragmentation Chain Transfer (RAFT) and high-temperature polymerization. RAFT polymerization of NIPAM, styrene and AA followed by aminolysis resulted in thiol-functionalized PNIPAM, PS and PAA. The high-temperature polymerization of iBoA resulted in PiBoA functionalized with Ene moiety. The characterization of the synthesized homopolymers was performed using 1H NMR spectroscopy, UV–vis spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy and size exclusion chromatography (SEC). In order to synthesize amphiphilic block copolymers, TEMPO initiated thiol-ene reaction was utilized for the conjugation of a thiol-functionalized block with an Ene functionalized block. The progress of thiol and ene conjugation was monitored via1H NMR spectroscopy. Based on 1H NMR results, quantitative conversions were obtained in 16 h under ambient conditions. The synthesized amphiphilic block copolymers were characterized using variety of techniques, for example, 1H NMR spectroscopy, UV–vis spectroscopy, SEC, FT-IR spectroscopy, Atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), Zeta potential and dynamic light scattering (DLS).