Carrier-assisted dyeing of poly( l -lactic acid) fibers with dispersed photochromic spiropyran dyes

Abstract The effects of dyeing carriers on the color strength (K/S values) of poly( l -lactic acid) (PLLA) fibers were investigated, using the photochromic dye 1′,3′,3′-trimethyl-6-nitro-spiro(2H-1-benzopyran-2,2′-indole) (6-nitro BIPS). Both an organic solution (based on tetrachloroethylene) and an aqueous dispersion of the dye were applied to the PLLA fibers, and the resulting change in color of the PLLA samples irradiated by ultraviolet (UV) light was evaluated by spectrocolorimetry. In the case of aqueous dispersion processing, the uptake of 6-nitro BIPS on the PLLA fibers was expected to be increased when using o-phenylphenol as a carrier. The value was four times higher than that obtained using the organic solution. The energy diagrams associated with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the 6-niro BIPS for the two dyeing processes were determined using photoelectron yield spectroscopy.