Preparation of Fast Photoresponsive Cellulose and Kinetic Study of Photoisomerization

Exploitation of a polymer carrier for introducing photochromic properties to cellulose matrix has several advantages such as photostability, photoreversibility, elimination of dye aggregation, and elimination of undesirable negative photochromism. The switching rate of a photochromic compound in the polymer matrix depends on steric restrictions, polarity, protic characteristics, and flexibility of the surrounding media. Here, the copolymerization of a spiropyran-based monomer with butyl acrylate and methyl methacrylate comonomers is reported through semicontinuous emulsion polymerization and the kinetics of isomerization and switching rate are investigated. The obtained latex was incorporated into cellulosic paper through chemical modification. The analysis confirmed a ring-opening reaction between hydroxyl groups in cellulose and epoxy functional groups in the low T-g latex. Morphological studies and contact angle measurements demonstrated an improved uniformity and enhanced hydrophobicity in the modified cellulose. Solid state UV-vis spectroscopy was employed to determinate the switching rate, kinetics analyses, maximum reflection wavelengths, and removal of undesired negative photochromism. Analyses revealed that flexible epoxy-functionalized photochromic modified cellulose exhibited reasonable fatigue resistance, photoresponsivity, and photoreversibility upon alternative UV and visible irradiation.