Reversible heat-set four-phase transitions of gel1-to-sol1-to-gel2-to-sol2 in binary hydrogels

IF 4.3 3区 工程技术 Q2 ENGINEERING, CHEMICAL
Mengjiao Liang, Wenwen Cao, Yaodong Huang
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引用次数: 0

Abstract

A class of supramolecular binary hydrogels is formed from dodecylamine or tridecylamine and sparing carboxylic acids (with amine/acid molar ratio ⩾ 18). These hydrogels exhibit a remarkable thermally reversible four-phase transition. On heating, they transition from gel one (G1)-to-sol one (Sol1), then to gel two (G2)-to-sol two (Sol2). On cooling, they revert from Sol2-to-G2-to-Sol1-to-G1. Additionally, several G1 and G2 hydrogels undergo thermally reversible gel-to-gel phase transitions, which are reflected by translucent-opaque and opaque-translucent changes in their appearance. The nature of the four-phase transformation was analyzed using a range of techniques. Scanning electron microscopy images confirmed that the fibers of the opaque hydrogel at high temperatures were considerably larger than those of its translucent counterpart at low temperatures. Fluorescence emission spectra demonstrated that higher temperatures, higher amine/acid ratios, and greater acid hydrophobicity increased the hydrophobic interactions. Fourier transform infrared spectroscopy and ultraviolet-visible spectroscopic analyses confirmed the existence of hydrogen-bonding interactions and aggregation in the hydrogels. X-ray diffraction profiles indicated that the hydrogels adopt lamellar structures. The findings advance our current understanding of the phase transition of supramolecular gels and facilitate the constitution of binary or multicomponent gels, providing a practical way to create new smart functional materials.

二元水凝胶中凝胶1-溶胶1-凝胶2-溶胶2的可逆热固四相转变
有一类超分子二元水凝胶是由十二胺或十三胺和疏羧酸(胺/酸摩尔比⩾ 18)形成的。这些水凝胶表现出显著的热可逆四相转变。加热时,它们从凝胶一(G1)转变为溶胶一(Sol1),然后转变为凝胶二(G2),再转变为溶胶二(Sol2)。冷却时,它们又从 Sol2 到 G2 再到 Sol1 到 G1。此外,几种 G1 和 G2 水凝胶还发生了凝胶到凝胶的热可逆相变,这反映在其外观的半透明-不透明和不透明-半透明变化上。我们使用一系列技术分析了四相转变的性质。扫描电子显微镜图像证实,高温下不透明水凝胶的纤维比低温下半透明水凝胶的纤维大得多。荧光发射光谱显示,较高的温度、较高的胺/酸比例和较强的酸疏水性增加了疏水相互作用。傅立叶变换红外光谱和紫外可见光谱分析证实了水凝胶中存在氢键相互作用和聚集现象。X 射线衍射曲线表明,水凝胶采用了片层结构。这些发现推进了我们目前对超分子凝胶相变的理解,促进了二元或多组分凝胶的形成,为创造新型智能功能材料提供了实用途径。
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来源期刊
CiteScore
7.60
自引率
6.70%
发文量
868
审稿时长
1 months
期刊介绍: Frontiers of Chemical Science and Engineering presents the latest developments in chemical science and engineering, emphasizing emerging and multidisciplinary fields and international trends in research and development. The journal promotes communication and exchange between scientists all over the world. The contents include original reviews, research papers and short communications. Coverage includes catalysis and reaction engineering, clean energy, functional material, nanotechnology and nanoscience, biomaterials and biotechnology, particle technology and multiphase processing, separation science and technology, sustainable technologies and green processing.
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