Side-Chain Amino-Acid-Derived Cationic Chiral Polymers by Controlled Radical Polymerization

There is an increased interest in incorporation of naturally occurring amino acid/peptide moieties into the synthetic polymeric chain. Because of functional group diversity in amino acids, it is possible to synthesize a large variety of well-defined functional amino-acid/peptide-based optically active polymers with varied polymer length, composition, and architectures using available controlled/living polymerization techniques. The amino acid inclusion into the synthetic polymer chains may offer several advantages such as (a) functional group availability which not only results in improved hydrophilicity and possible interactions with proteins and genes but also facilitates further modification with bioactive molecules, (b) introduces chirality, and (c) makes room for noncovalent interactions to form hierarchical superstructures. From the long past, amino acids have been extensively incorporated in the main chain of biodegradable polymers, and their biological importance have been evaluated. Besides, various side-chain amino-acid/peptide-bearing polymers have been synthesized and used for different purposes. In this article, utilization of different controlled/living polymerization methods to prepare various side-chain amino acid/peptide pendant polymers will be discussed, mainly focusing on cationic chiral polymeric architectures and 3D gel networks by reversible addition–fragmentation chain transfer polymerization.