Alternating placement of d‐ and l‐alanine moieties in the polymer side‐chains.

Abstract

Synthesis of a sequence-controlled polymer via reversible addition-fragmentation chain transfer polymerization is reported herein, using an N-substituted maleimide monomer bearing tert-butyl carbamate (Boc)-protected l-alanine (M1) and Boc-d-alanine appended styrenic monomer (M2). The monomer sequence distribution along the polymer chain is thoroughly studied by 1H and 13C NMR spectroscopy and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, confirming the alternating placement of l-alanine and d-alanine throughout the polymer chain. Copolymers display fluorescence properties in various organic solvents. After the deprotection of Boc-groups, the copolymers show fluorescence activity in water (and also in several organic solvents), and pH-responsiveness in aqueous medium due to the protonation/deprotonation of the side-chain -NH2 groups at varying aqueous solution pH. In addition, the presence of different enantiomeric structures of alanine in the side-chain enables us to investigate the chiroptical properties of the polymers.