Photoluminescent poly(4-vinylpyridine)-based ionic liquids coded with L- and D-histidine: a supramolecular self-assembly leading to the formation of red-shifted photoluminescent helical aggregates
Herein, photoluminescent poly(4-vinylpyridine)-based ionic liquids (PILs) bound with D- and L-histidine were synthesized for the first time and fully characterized by NMR, IR and UV-vis spectroscopy and TG analysis. The chiral PILs self-assembled into helical aggregates, which were isolated by two different methods, namely, by the addition of a poor solvent and by the slow evaporation of solvent. The isolated nanofibers, comprising helical aggregates, were observed to be thin in the case of the former and thick in the case of the latter method. Moreover, the helical nanofibers formed herein were several hundreds of micrometers long. The aggregation of the PIL chains in the helical nanofibers was further revealed by the significantly red-shifted photoluminescence spectra.