Photochromism of Poly(lactic acid) Mixed with 9,10-Anthraquinone

Abstract

The color change from pale yellow to vermilion due to the UV-irradiation and the reverse color change due to the heating at about the glass transition temperature (T_g) were investigated for the poly(lactic acid) (PLA) mixed with 9,10-anthraquinone (AQ) by electronic absorption and IR analysis. The absorption of the broad band around 485 nm assigned to the electron donor acceptor (EDA) between AQ and anthrahydroquinone (AQH₂) was increased by UV-irradiation and was decreased by the heating at about the glass transition temperature. The color change and reversion was possible by repeating the UV irradiation and the heating operations. A decrease of AQ and a formation of AQH₂ by the UV irradiation and a increase of AQ and a small decrease of AQH₂ by the heating were observed from the IR measurements. The formation of the AQ-AQH₂EDA complex which hydrogen bonded with PLA was a cause of coloration and the dissociation of EDA was a cause of fading. At the same time, some of AQH₂ was oxidized to AQ.