Highly transparent poly(stearyl methacrylate)-poly(2,2,2-trifluoroethyl methacrylate) (PSMA-PTFEMA) diblock copolymer spheres of 33 nm diameter are prepared via polymerization-induced self-assembly (PISA) in non-polar media. This was achieved by chain-extending a PSMA precursor via RAFT dispersion polymerization of TFEMA in n-tetradecane at 70 °C. This PISA formulation is isorefractive which enables visible absorption spectra to be recorded with minimal light scattering even at 30 % w/w. However, in situ monitoring of the RAFT end-groups during PISA requires utilising a weak n→π* band at 446 nm. Conversion of TFEMA into PTFEMA causes a contraction in solution volume, leading to an initial increase in absorbance that enables the kinetics of polymerization to be monitored via dilatometry. At ~98% TFEMA conversion, this 446 nm band remains constant for 2 h at 70 °C, indicating high RAFT chain-end fidelity under monomer-starved conditions. Addition of excess initiator at 70 °C leads to RAFT chain-end removal with no change in nanoparticle morphology. We have also examined the kinetics of removal of dithiobenzoate RAFT end-groups from PSMA-PTFEMA spheres. Finally, we have designed highly transparent PSMA-PTFEMA worms and vesicles using the same refractive index matching approach.

In situ spectroscopic studies of highly transparent nanoparticle dispersions enable assessment of trithiocarbonate chain-end fidelity during RAFT dispersion polymerization in non-polar media

2019 Fall National Meeting

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