Clusterization-triggered emission, stimulus-responsiveness, and DNA polyplex formation of poly(vinylamine)-based chiral block and random copolymers

Random and block copolymers exhibiting clusterization-triggered emission (CTE) and consisting of vinylamine (VAm) and methylated N-acryloyl-L-threonine (AThrOMe) were developed. They showed unique stimulusresponsiveness and polyplex-formation-induced changes in emission properties. The random and block copolymers, P(VAm-co-AThrOMe) and PVAm-b-PAThrOMe, contained no traditional fluorescent aromatic molecules, whereas the aggregation of VAm units within the assembled structures appeared to be a powerful tool for achieving enhanced fluorescence signals. The concentration-, wavelength-, and solvent-polarity-dependent emission behaviors of the VAm/AThrOMe copolymers could be tuned by implementing a rational molecular design (random or block sequence). The assembled structures and chiroptical and emission properties in response to external stimuli (temperature change and addition of salt and urea) in an aqueous solution were investigated using dynamic light scattering, circular dichroism, and fluorescence measurements. Selective interactions of DNAs with the VAm units in the VAm/AThrOMe copolymers were evaluated by performing agarose gel electrophoresis; these interactions affected the assembled structures and chiroptical and CTE properties. The comonomer sequence, external stimuli, and interactions with DNAs affected the aggregated states of the VAm unit in the copolymers, thereby showing that CTE behaviors can be manipulated in future sensing applications.