The efficient synthesis of amine-functional diblock copolymer nano-objects via RAFT alcoholic dispersion polymerization has been recently reported. Benzyl methacrylate (BzMA) is polymerized in ethanol using a poly(2-(dimethylamino)ethyl methacrylate) (PDMA) chain transfer agent at 70�C. Depending on the packing parameter, p, polymerization-induced self-assembly (PISA) can produce spherical micelles, worm-like micelles or vesicles. High monomer conversions (> 99% by 1H NMR) are achieved within 24 h, while THF GPC studies indicate low copolymer polydispersities (Mw/Mn < 1.30), suggesting good pseudo-living character. When transferred from ethanol to water, the nanoparticles remain colloidally stable and acquire appreciable cationic character, as judged by DLS and aqueous electrophoresis studies respectively. Utilising an ethanol/water mixture leads to a significantly faster rate of BzMA polymerization, with 80% conversion being achieved at 70oC within 7 h. This is presumably because water is a poor solvent for the BzMA monomer, which partitions into the growing micelles; thus enhancing the local monomer concentration and increasing the polymerization rate. Moreover, the addition of water also affects the final copolymer morphology, with only kinetically-trapped spherical micelles being obtained when targeting diblock compositions that produce well-defined vesicles when utilizing pure ethanol. This suggests possible protonation of the PDMA stabilizer chains in the presence of water. The resulting charge repulsion between neighbouring chains means that more asymmetric diblocks (i.e. longer PBzMA blocks for a fixed PDMA block) are needed to achieve non-spherical morphologies.

Addition of water to an alcoholic RAFT PISA formulation affects both polymerization kinetics and copolymer morphology

248th National Meeting (2014)

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