Anthracene based photo-tunable polymers with excimer emission

The aggregation properties of a diblock and a triblock copolymer in the aqueous phase has been investigated by photophysical and microscopy methods. Both copolymers possess photoresponsive hydrophobic poly(9-anthrylmethyl methacrylate) (PAN) block and hydrophilic polyethylene oxide (PEO) block whereas the triblock copolymer have an additional polystyrene (PSt) block at the middle. The amphiphilic copolymers, PAN-bPEO and PAN-b-PSt-b-PEO, were synthesized by atom transfer radical polymerization (ATRP) method. Self assembly of these individual copolymers in water leads to the formation of uniform spherical supramolecular assemblies. The morphology of the resultant spheres was disturbed by the illumination of the turbid aqueous solutions with 360 nm UV light accomplished by the photosolvolysis of the anthracenylmethyl ester. This irreversible photodissociation virtually transforms the amphiphilic diblock copolymer to a double hydrophilic block copolymer whereas the triblock copolymer because of its central PSt block was transformed into a bolaamphiphile. Complete micellar dissociation obtained in the case of diblock was not observed in the case of vesicular aggregates of the triblock copolymer. We also found that compared to the completely dissolved state, aggregation resulted in the pronounced excimer emission of the anthracene copolymers.

Automated summary

The aggregation properties of diblock and triblock copolymers in the aqueous phase were investigated using photophysical and microscopy methods. Both types of copolymers form uniform spherical supramolecular assemblies in water, with the triblock copolymer containing an additional polystyrene block. Light-induced photodissociation altered the morphology of the copolymers, transforming the diblock copolymer into a double hydrophilic block copolymer and the triblock copolymer into a bolaamphiphile. Micellar dissociation was observed in the diblock copolymer, but not in the vesicular aggregates of the triblock copolymer. Additionally, aggregation resulted in pronounced excimer emission of the anthracene copolymers compared to the completely dissolved state.