Synthesis of diblock copolymer spheres, worms and vesicles via RAFT aqueous emulsion polymerization of hydroxybutyl methacrylate

Saul J Hunter,Oleksandr O Mykhaylyk,Joseph R Lovett,Steven P Armes,Elizabeth R Jones

doi:10.1039/d1py00517k

Abstract

RAFT aqueous emulsion polymerization of hydroxybutyl methacrylate using a poly(glycerol monomethacrylate) precursor leads to diblock copolymer spheres, worms or vesicles. A pseudo-phase diagram is constructed and the vesicles are briefly evaluated as a Pickering emulsifier.

Highlights

The non-ionic PGMA41-PHBMAx diblock copolymer chains prepared do not require any methylation prior to Gel permeation chromatography (GPC) analysis, unlike the anionic PMAA-PHBMA copolymer chains prepared by Cockram and co-workers.[44]
The polymerization-induced self-assembly (PISA) synthesis of PGMA41-PHBMA60 at 15% w/w produces a pure worm phase (Fig. 2b), whereas targeting the Scheme 1 reversible addition–fragmentation chain transfer (RAFT) aqueous emulsion polymerization of hydroxybutyl methacrylate (HBMA) (N.B. this monomer comprises a 1 : 1 mixture of the 2- and 4-isomers but only the latter is depicted in this scheme) using a PGMA41 precursor provides convenient access to diblock copolymer spheres, worms or vesicles depending on the target degree of polymerization (x) for the PHBMA block
A rather subtle change in monomer structure leads to the aqueous solubility of HBMA being approximately four times lower than that of hydroxypropyl methacrylate (HPMA), which represents the difference between aqueous emulsion polymerization and aqueous dispersion polymerization, respectively

Summary

Introduction

Over the past two decades, there has been considerable interest in using controlled living radical polymerization techniques to prepare amphiphilic diblock copolymers in the form of nanoparticles in aqueous media via polymerization-induced self-assembly (PISA).[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15] PISA occurs in situ when a watersoluble homopolymer is chain-extended with an appropriate second monomer. The PISA synthesis of PGMA41-PHBMA60 at 15% w/w produces a pure worm phase (Fig. 2b), whereas targeting the Scheme 1 RAFT aqueous emulsion polymerization of HBMA (N.B. this monomer comprises a 1 : 1 mixture of the 2- and 4-isomers but only the latter is depicted in this scheme) using a PGMA41 precursor provides convenient access to diblock copolymer spheres, worms or vesicles depending on the target degree of polymerization (x) for the PHBMA block.

Results

Conclusion