{"title":"Reversible heat-set four-phase transitions of gel1-to-sol1-to-gel2-to-sol2 in binary hydrogels","authors":"Mengjiao Liang, Wenwen Cao, Yaodong Huang","doi":"10.1007/s11705-024-2501-6","DOIUrl":null,"url":null,"abstract":"<div><p>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 (G<sup>1</sup>)-to-sol one (Sol<sup>1</sup>), then to gel two (G<sup>2</sup>)-to-sol two (Sol<sup>2</sup>). On cooling, they revert from Sol<sup>2</sup>-to-G<sup>2</sup>-to-Sol<sup>1</sup>-to-G<sup>1</sup>. Additionally, several G<sup>1</sup> and G<sup>2</sup> 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.</p><div><figure><div><div><picture><source><img></source></picture></div></div></figure></div></div>","PeriodicalId":571,"journal":{"name":"Frontiers of Chemical Science and Engineering","volume":null,"pages":null},"PeriodicalIF":4.3000,"publicationDate":"2024-09-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Frontiers of Chemical Science and Engineering","FirstCategoryId":"5","ListUrlMain":"https://link.springer.com/article/10.1007/s11705-024-2501-6","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"ENGINEERING, CHEMICAL","Score":null,"Total":0}
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.
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.