Widely commercialized for imaging and biological applications, fluorescent dyes are often large molecules containing aromatic rings and have a low solubility. Dithiomaleimide (DTM) was found to be a highly emissive fluorescent functionality and was used to label proteins, polymers and nanoparticles. The DTM motif can also be incorporated into a block copolymer as a part of a dual initiator for ring opening polymerization (ROP) and reversible addition-fragmentation chain transfer polymerization (RAFT). In this case, the amphiphilic block-dye-block copolymer is constituted of poly(D,L-lactide) (PLA) as the hydrophobic segment and poly(triethyleneglycol monomethyl ether methacrylate) (PTEGA) as the hydrophilic segment. The self-assembly of this amphiphilic block copolymer into spherical micelles in water ensures the location of DTM functionality at the micelles’ core/shell interface. The reactivity of the DTM functional group was used to induce a morphology transition from spherical micelles to vesicles, simultaneously with an ON-to-OFF fluorescence emission switch. This transition is the result of a thiol exchange reaction, which occurs in the presence of an excess of thiol in the environment; the PLA segment is substituted with thiophenol. The transition was observed <i>via in situ</i> SAXS measurements, showing a morphology change within 10 min, which is consistent with fluorescence spectroscopy results. The vesicles’ formation was also confirmed by multi-angle laser light scattering.

Dual effect of thiol addition on fluorescent polymeric micelles: ON-to-OFF emissive switch and morphology transition

253rd National Meeting (2017)

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