Preparation of amphiphilic block copolymer containing triazene moieties and fluorescence study

Abstract

The present study describes the synthesis via microwave accelerated reversible addition-fragmentation chain transfer (RAFT) polymerization of an amphiphilic block copolymer poly(acrylic acid)-b-poly(dodecylacrylamide-co-1-(phenyl)-3-(2-methacryloyloxyethyl carbamoyloxyethyl)-3-methyltriazene-1) [PAA-b-(PDA-co-PUMA-T)]. The structure and the chemical composition of the block copolymer were confirmed by spectral/thermal analysis. The photoreactivity of the triazene sequences from PAA-b-(PDA-co-PUMA-T) was quantified by UV/vis irradiation in chloroform/dimethylformamide solutions and in thin film, indicating that the solvent polarity modifies with an order of magnitude the rate constant values. The lower rate constant in film state (\(k_{\rm film} = 1.3 \times 10^{-3}\) s − 1), shows that the higher mobility of polymeric chains in solution allow a more rapid orientation, favourable to the triazene bond cleavage. The capability of block copolymer to form micelles in aqueous environment and implicitly, its critical micelle concentration (CMC) was evidenced through fluorescence measurements using pyrene probe (10 − 6 M), the CMC value being of 4.64 ×10 − 3 g L − 1 PAA-b-(PDA-co-PUMA-T) (3.27 ×10 − 7 M). Experiments of fluorescence quenching with various metal cations (UO\(_{2}^{2+}\), Fe2 + , Fe3 + , Ni2 + , Cu2 + , Co2 + , Pb2 + and Hg2 + ) suggested that such a block copolymer could find applications as fluorescence-based chemosensor for the detection of iron cations in homogeneous organic solutions or aqueous environments by thin films. Photosensitive amphiphilic block copolymer bearing triazene sequences was synthesized via microwave accelerated RAFT polymerization. The photolability of triazene units and the formation micelles in aqueous environment were studied, while fluorescence quenching in the presence of various metal cations show that such block copolymer could find applications as fluorescence-based chemosensor.