Fluorescent labelled dual-stimuli (pH/thermo) responsive self-assembled side-chain amino acid based polymers.

Abstract

Pyrene labelled chain transfer agent, py-CTA, was synthesized and employed for the reversible addition-fragmentation chain transfer (RAFT) polymerization of Boc-phenylalanine/alanine methacryloyloxyethyl ester (Boc-F/A-EMA) based monomers, for obtaining α-pyrene labelled homopolymers, pyrene-poly(Boc-phenylalanine/alanine methacryloyloxyethyl ester) (py-P(Boc-F/A-EMA)), with controlled molecular weight, narrow polydispersity and precise chain-end functionality. Subsequent Boc-deprotection produced pH-responsive cationic homopolymers with side-chain primary amino groups. Furthermore, py-P(Boc-F/A-EMA) was utilized as macro-CTA for the polymerization of di(ethylene glycol) methyl ether methacrylate (DEGMA) to afford block copolymers, which upon Boc-deprotection provided dual pH- and thermo-responsive polymers. An interplay of hydrophobicity of the incorporated amino acid residue as well as pH value of the solution were determined as the tunable parameter for the alteration of lower critical solution temperature (LCST) of these block copolymers. Functionalization of carbon nanotube (CNT) via non-covalent interactions, and unique morphologies generated from the self-assembly of these synthetic macromolecules were also investigated.