Self-assembly of chromogenic dyes?a new mechanism for humidity sensors

The design, fabrication and characterization of a novel type of humidity sensing polymer are presented. The new material was prepared by incorporating a chromogenic, cyano-substituted oligo(p-phenylene vinylene) dye into a polyamide by quenching the blend from the melt. Exposure of these kinetically trapped, molecularly mixed blends to water plasticizes the amorphous phase and leads to aggregation of the dye molecules, concomitant with pronounced and irreversible changes of the material's absorption and fluorescence color.