Morphological evolution of poly(glycerol monomethacrylate)-stat-glycine-phenylalanine-phenylalanine-methacrylamide-b-poly(2-hydroxypropylmethacrylate) (P(GMA-stat-(MAm-GFF))-b-PHPMA) block copolymer nano-objects via polymerization-induced self-assembly

Abstract

Here we report a study on the reversible addition-fragmentation chain transfer (RAFT) polymerization-induced self-assembly (PISA) of self-assembling peptide-containing diblock copolymers. The self-assembling tripeptide (SAP) monomer used (MAm-GFF) is a methacrylamide-functionalized Gly-Phe-Phe sequence. The incorporation of this self-assembling GFF tripeptide into the stabilizing PGMA segment of a well-known poly(glycerol monomethacrylate)-b-poly(2-hydroxypropyl methacrylate) block copolymer (PGMA-b-PHPMA) has been shown in a previous study to induce the formation of complex self-assembled structures. The present article explores the effect of varying the block length (both hydrophilic and hydrophobic blocks), block composition (different SAP units in the hydrophilic block), solvent composition and temperature on the morphologies of PISA synthesized P(GMA-stat-(MAm-GFF))-b-PHPMA. The polymerization of HPMA from the SAP-containing P(GMA-stat-(MAm-GFF)) stabilizing block led to well-defined diblock copolymers, which self-assembled into diverse morphologies ranging from vesicles, worms, or micelles to unreported highly anisotropic structures. Moreover, these morphologies were found to be thermoresponsive. At 70 °C, more classic morphologies were observed as hydrogen bonds are weakened at high temperatures. However, these structures transform into unprecedented morphologies (urchin-like) once cooled to 4 °C probably due to the reduced hydrophilicity of the PHPMA block.