Exploring the post-polymerization modification of side-chain amino acid containing polymers via Michael addition reactions

An efficacious protocol for the aza-Michael addition of a C-terminus modified phenylalanine side-chain containing polymer (Michael donor) was demonstrated with various Michael acceptors. The aza-Michael addition reactions were carried out at 50 °C in anhydrous methanol, which is a protic solvent, to enhance the advancement of the reactions. 1H and inverse gated 13C NMR spectroscopy were utilized to qualitatively deliver comprehensive data on the reaction progress. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) provided quantitative information about the modification of the polymer. The extent of change in the aza-Michael addition varied with different Michael acceptors and decreased in the order of acrylate > acrylamide > methacrylate. The present study opens up a library of polymers with functional modifications in the side-chain.