High-throughput experimentation is well established in pharmaceutical research. More recently, it has been applied to polymer science, not least because a large number of parameters can be screened during synthesis. One rapidly growing area of polymer science is the synthesis of a wide range of diblock copolymer nanoparticles via polymerization-induced self-assembly (PISA). In the present work, reversible addition-fragmentation chain transfer (RAFT) aqueous emulsion polymerization formulations were optimized for use in conjunction with a high-throughput Chemspeed A100 robot. More specifically, a poly(methacrylic acid)-based macro-CTA (PMAA56) was chain-extended in turn using benzyl methacrylate (BzMA), n-butyl methacrylate (BMA), methyl methacrylate (MMA) or (4-hydroxybutyl methacrylate (HBMA); this series of four methacrylic monomers was deliberately selected to cover a range of monomer solubilities and densities. Optimized reaction conditions utilized a propeller stirrer at 550 rpm targeting a core-forming block DP of 500 in mildly acidic aqueous solution (pH 5) at 70 oC. In a second series of experiments, a small library of various triblock and tetrablock copolymer nanoparticles were prepared via a one-pot PISA protocol using sequential monomer addition. In this case, the same PMAA56 macro-CTA was chain-extended with BzMA, followed by BMA and then (in the case of the tetrablocks) BzMA, with each insoluble block having a target DP of 500. The order of the core-forming blocks was also reversed; the PMAA56 macro-CTA was chain-extended first with BMA, followed by BzMA and then BMA. Such PISA syntheses were completed within 3 h for the triblocks (40 w/w % solids; final conversions = &gt; 99 %) and 5 h for the tetrablocks (45 w/w % solids; final conversions ranging from 88 to 97 %). TEM and DLS studies confirmed that colloidally stable spherical nanoparticles were obtained in all cases. These preliminary studies provide the basis for further high-throughput screening of RAFT-mediated PISA formulations, which is likely to be required for commercialization of this technology.

Multiblock copolymer nanoparticles synthesized via RAFT aqueous emulsion polymerization using a high-throughput robot

255th National Meeting (2018)

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