PLLA-Based Block Copolymers via Raft Polymerization—Impact of the Synthetic Route and Activation Mechanism

Abstract

Designing supramolecular structures with well-defined dimensions and diverse morphologies via the self-assembly of block copolymers is renowned. Specifically, the design of 1D fiber nanostructures is extensively emphasized, due to their unique properties in many areas, such as microelectronics, photonics, and particularly in the biomedical field. Herein, amphiphilic diblock copolymers of P(l-lactide)-b-P(N-t-butoxy-carbonyl-N´-acryloyl-1,2-diaminoethane)-co-P(N-isopropylacrylamide) PLLAn-b-P(BocAEAm)m-co- P(NiPAAm)Ɩ are developed. Two synthetic strategies are investigated to equip PLLA with a chain transfer agent (CTA), either by Steglich esterification of PLLA-OH or via the ring-opening polymerization of l-lactide using a CTA containing a hydroxyl functional group. The second strategy proves to be superior in terms of degree of functionalization. The corona-forming blocks, with degrees of polymerization of 200 and above are achieved in good definition by photo-iniferter RAFT polymerization (Đ ≤ 1.25), while a Đ of 1.75 is obtained by conventional RAFT polymerization. The self-assembly of the developed system leads to the formation of nanofibers with a height of 11 nm and a length of ≈300 nm, which is determined by atomic force microscopy (AFM). These fibers are the basis for new antimicrobial nanomaterials after deprotection, as the subject of upcoming work.