作者:Masako Akazawa、Kingo Uchida、Jaap J. D. de Jong、Jetsuda Areephong、Marc Stuart、Giuseppe Caroli、Wesley R. Browne、Ben L. Feringa
DOI:10.1039/b802580k
日期:——
Dithienylperhydrocyclopentene-bisurea-based low molecular weight gelators are described that function as photoresponsive organogels that show a remarkable gel-to-liquid transition upon irradiation. The two series of derivatives, with and without alkyl spacers between the urea hydrogen bonding groups and the photochromic unit, show different gelation behavior. Upon UV irradiation of the gels, a gel liquified at only 1.4% conversion of the photochromic unit. Transmission electron microscopy (TEM) shows that the gel fibres consist of thin ribbons. Semi-empirical (PM3) calculations indicate that the hydrogen bonding between the open-ring isomer (o) molecules is weak, and that formation of the closed-ring isomer (c) destabilises the hydrogen bonding further. The results indicate that a small amount of the closed-ring isomer will disrupt the intermolecular hydrogen-bonding, leading to disintegration of the gel fibre ribbons and hence reversible liquification.
描述了一种基于二噻吩-过氢环戊烯-双脲的低分子量凝胶剂,这些凝胶剂作为光响应有机胶表现出显著的凝胶-液体转变。在两系列衍生物中,带有和不带有尿素氢键基团与光致变色单元之间的烷基间隔的,表现出不同的胶化行为。在紫外光照射下,凝胶在光致变色单元仅1.4%的转化下就发生了液化。透射电子显微镜(TEM)显示凝胶纤维由细长的带状结构组成。半经验(PM3)计算表明,开环异构体(o)分子之间的氢键相对较弱,而闭环异构体(c)的形成进一步破坏了氢键的稳定性。结果表明,少量闭环异构体会破坏分子间的氢键,从而导致凝胶纤维带的解体,因此实现可逆液化。