Session:

Smart textiles are emerging innovations adding technology to the basic textiles known. Many industries require the use of textiles that can accommodate and support their niche functions and environmental demands. A subset of smart textiles includes photochromic textiles. Photochromic dye molecules are situated into textiles to create commonly done via microcapsules or implementing traditional dye methods. Once integrated and stimulated by a light source, the photofunctionality is induced in the polymer matrix and can also be reversed. This reversibility can occur through heat activation or light irradiation, classifying the photochromic molecules as either T-Type or P-Type, respectively. Donor-Acceptor-Stenhouse-Adducts (DASAs) are a recent discovery of photochromic photoswitches that can be integrated in a variety of materials to advance the efficacy of smart textiles. Compared to other photoswitching molecules, DASAs offer advantages such as easier synthesis, hydrophilic-hydrophobic molecular micelle stability, high yield, fatigue resistance, and fine tunability. The simplified mechanism of DASAs isomerizes a colored, hydrophobic linear molecule into a colorless, hydrophilic cyclic version via visible light irradiation. Heat can then be applied to induce the cyclic to linear DASA reversibility of the T-type photochromic molecule. Upon its discovery, DASAs have been studied into generations to better understand its utilities, improve their limitations, and extend their capabilities. DASAs offer a platform of photoswitching capabilities that can be integrated in a variety of materials to advance the efficacy of smart textiles. In first generation DASAs, the donor-acceptor structure is composed of an alkyl amine with typically either a Meldrum’s acid or barbituric acid. Successful and effective self-assembly and reversibility for first generation DASAs are reliant on solvent choice. Different solvents can either drive or inhibit the mechanisms at which the DASA enters a phase change in the photoswitching process. DASA photoswitching has been successfully demonstrated on polymers and surfaces from DASA modified polydopamine coated silica micro/nanoparticles on glass substrates to DASA-azobenzene-polystyrene mix on glass substrate to DASAs onto TiO₂ anatase surfaces but not on textiles. First generation DASAs are integrated on cotton for the first time via a two-step assembly approach. Cotton fabric is amine functionalized via the attachment of N, N-methyl(2-bromo-ethyl) ammonium bromide, creating secondary amines on the cotton samples. Then, the DASA compounds, 5-(furan-2-ylmethlene)-2,2-dimethyl-1,3-dioxane-4,6-dione, are self-assembled onto the cotton fabric. DASAs aggregate and stabilize themselves onto the cotton samples. Environmental stimuli such as visible light irradiation, water, and heat were induced onto the DASA-modified samples to understand the photochromic intensities and reversibility in unique situations. The confirmation of successful DASA attachment was confirmed through characterization and measurements including H-NMR and C-NMR spectroscopy, FTIR, and CIELAB Color Space (L*a*b). The characterizations and measurements displayed successful immobilization of first generation DASAs onto cotton. The stimuli induced onto the modified cotton gave insights into how DASAs on cotton could respond on a larger scale in various environments.

Co-Author(s): Juan Hinestroza (Cornell University)

Jennifer Leung

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