Addition of water to the ethanolic RAFT PISA synthesis of poly(2-(dimethylamino)ethyl methacrylate)-poly(benzyl methacrylate) (PDMA-PBzMA) diblock copolymer nanoparticles was explored in order to enhance the rate of BzMA polymerization and so overcome the problem of incomplete monomer conversion when targeting higher mean degrees of polymerization. Significantly faster polymerizations were observed: 90 % BzMA conversion was achieved within just 6 h in the presence of 20 % w/w water, compared to 35 % in anhydrous ethanol. This rate enhancement is attributed to unreacted BzMA preferentially entering the micelles following nucleation, thus increasing both the local monomer concentration and the rate of BzMA polymerization. When using a relatively short PDMA chain transfer agent, adjusting the solvent composition also affected the final copolymer morphology. Aqueous electrophoresis studies suggest that the PDMA stabilizer chains acquire partial cationic charge. This leads to more efficient inter-particle repulsion, thus preventing the sphere-sphere fusion events required for an evolution in morphology and so leading to kinetically-trapped spheres.

Investigating the effect of water as a co-solvent in an alcoholic RAFT PISA formulation

251st National Meeting (2016)

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