Alternating Placement of d‐ and l‐Alanine Moieties in the Polymer Side‐Chains

Abstract

AbstractSynthesis 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.