Sol–Gel Phase Transitions in a Photochromic Spiropyran-Modified Material by Incorporation in a Hydrogel
Abstract:Photochromic spiropyran-modified material 1 and hydrogelator 2 bearing sugar and D-alanine moieties were prepared and their thermal- and photo-responsive properties in aqueous solution were investigated by NMR, CD, PXRD, DSC, and UV–vis spectroscopy. The xerogels [1 + 2] (1:1–20 wt%) with various ratios obtained from water showed well-developed fibril structures with diameters of 50–100 nm and length of several hundred micrometers. Interestingly, after irradiation with UV light, these aggregates were destroyed because the closed form (SP) of spiropyran unit of 1 changes to the corresponding merocyanine form (MC). In contrast, further heating led to the original hydrogels [1 + 2], due to the transformation of the opened form (MC) of 1 into the corresponding spiropyran form (SP). Thus, the spiropyran unit of 1 played an important role in the gelation of water by interacting with the gelators in a host–guest interaction that could modify the superstructures and sensitively affect their stability.
Document Type: Short Communication
Publication date: October 1, 2009
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