A novel dual stimuli-responsive thiol-end-capped ABC triblock copolymer: synthesis via reversible addition-fragmentation chain transfer technique, and investigation of its self-assembly behavior

Abstract

A novel thermo- and pH-responsive thiol-end-capped ABC triblock copolymer, namely poly(acrylic acid)-block-poly(N-isopropylacrylamide)-block-poly(?-caprolactone)-SH (PAA-b-PNIPAAm-b-PCL-SH), was synthesized using a combination of ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization techniques. The chemical structures of all samples were characterized by means of Fourier transform infrared and 1H NMR spectroscopies. The molecular weight of each segment was investigated using both 1H NMR spectroscopy and gel permeation chromatography. The self-assembly behavior of the PAA-b-PNIPAAm-b-PCL-SH triblock copolymer under thermal and pH stimuli was fully investigated by means of fluorescence and UV-visible spectroscopies as well as dynamic light scattering measurements. The critical micelle concentration for the synthesized triblock copolymer was determined to be 0.0178 g L?1 using the fluorescence probe technique. The average size of PAA-b-PNIPAAm-b-PCL-SH micelles was determined to be 25 nm using transmission electron microscopy observations, and its lower critical solution temperature was determined to be 41-43 آ°C using UV-visible spectroscopy. é 2017 Society of Chemical Industry. é 2017 Society of Chemical Industry