Abstract

Photoresponsive supramolecular gels as intelligent non-invasive responsive materials can undergo changes in color, state, morphology and electronic properties upon photo irradiation, making them attractive for a variety of applications. Herein, a novel supramolecular hydrogelator DBE with 1,4-divinylbenzene as the central core, connected via amide linkage to l-phenylalanine and peripheral hydrophilic groups, was designed to evaluate the effect of [2 + 2] photocycloaddition reaction on supramolecular hydrogels. UV irradiation decreases the solubility of the hydrogelator DBE and hence, causes the destruction of the gel. SEM images clearly show that irradiation with UV light could induce disintegration of the right-handed helical nanofibers entangled network, which turns into nanoparticles and eventually massive crystals. Circular dichroism and vibrational circular dichroism data also indicate the formation of right-handed helical nanofibers in DBE gel. FTIR and MALDI–TOF–MS spectrum confirm that the variation of stability and aggregated morphology of DBE gel after UV irradiation is attributed to [2 + 2] cycloaddition reaction of vinyl units. This study presents a wonderful model for regulating the stability and aggregated morphology of supramolecular hydrogels via photo irradiation, as well as offers new ideas for designing novel photo responsive materials.

Graphic Abstract

中文翻译：

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[2 + 2]光环加成反应调节水凝胶的稳定性和形态

摘要

作为智能非侵入性响应材料的光响应超分子凝胶在光辐照时会发生颜色，状态，形态和电子特性的变化，从而使其在多种应用中具有吸引力。在此，一种新型的超分子水凝胶DBE与1,4-二乙烯基苯作为中央核心，通过酰胺键连接升-苯丙氨酸和周围的亲水基团，旨在评估[2 + 2]光环加成反应对超分子水凝胶的影响。紫外线照射会降低水凝胶化剂DBE的溶解度，因此会破坏凝胶。SEM图像清楚地表明，用紫外线照射可引起右旋螺旋纳米纤维纠缠网络的分解，从而变成纳米颗粒，最终成为块状晶体。圆二色性和振动圆二色性数据也表明在DBE凝胶中右旋螺旋纳米纤维的形成。FTIR和MALDI–TOF–MS光谱证实，紫外线照射后DBE凝胶的稳定性和聚集形态的变化归因于乙烯基单元的[2 + 2]环加成反应。

图形摘要