Stimulus-responsive non-ionic diblock copolymers: protonation of a tertiary amine end-group induces vesicle-to-worm or vesicle-to-sphere transitions

Nicholas J W Penfold,Steven P Armes,Joseph R Lovett,Pierre Verstraete,Johan Smets

doi:10.1039/c6py01076h

Abstract

Morpholine-functionalised poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) diblock copolymer vesicles are transformed into worms or spheres on lowering the solution pH.

Highlights

The self-assembly of AB diblock copolymers to afford nanoparticles has been of considerable interest to many research groups over the last fifty years
This watersoluble morpholine-functionalised trithiocarbonate-based chain transfer agent (MPETTC)-PGMA43 macro-CTA was subsequently chainextended with hydroxypropyl methacrylate (HPMA) at 56 °C using a reversible addition–fragmentation chain transfer (RAFT) aqueous dispersion polymerisation formulation to generate a series of four MPETTC-PGMA43-PHPMAy diblock copolymer vesicles (y = 190, 200, 220 or 230) at 10% w/w solids
Initial experiments confirmed that a diblock copolymer with a slightly lower core-forming block degree of polymerisation (DP) (MPETTC-PGMA43-PHPMA180) formed a vesicle/worm mixed phase, rather than pure vesicles

Summary

Introduction

The self-assembly of AB diblock copolymers to afford nanoparticles has been of considerable interest to many research groups over the last fifty years. Lovett and co-workers reported the complex stimulus-responsive behaviour of PGMA-PHPMA vesicles when subjected to a change in solution pH.[60] ionisation of a carboxylic acid end-group on each PGMA stabiliser block induced either a vesicle-to-worm or a vesicle-to-sphere transition, depending on the mean degree of polymerisation (DP) of the hydrophobic PHPMA block.

Results

Conclusion