Temperature and chemical environment effects on the aggregation extent of water soluble perylene dye into vinyl alcohol-containing polymers.

In this work, a water soluble perylene derivative containing piperazine peripheral units, i.e. N,N'-bis(2-(1-piperazino)ethyl)-3,4,9,10-perylenetetracarboxylic acid diimide dichloride (PZPER) was synthesized and dispersed at low loadings (from 0.1 to 1.1 wt%) into vinyl alcohol-containing polymer matrices. From the data acquired, the most effective driving force for the formation of intramolecular aggregates of PZPER was attributed to hydrogen bonding interactions. In particular, the aggregation extent was affected by the reduction of molecular interactions occurring in both solution and in polymer dispersions due to the decreasing polarity of the chromophore environment or increasing temperature. The sensitivity of PZPER aggregates dispersed into vinyl alcohol-containing polymer matrices towards mechanical stress was also reported. The responsiveness of PZPER optical properties (both in absorption and in emission) versus thermal or mechanical solicitations suggests applications of polymer dispersions as smart indicators to external stimuli.