Department of Chemistry, Indian Institute of Technology Kharagpur , Kharagpur 721 302, India.
Langmuir. 2014 Feb 18;30(6):1677-85. doi: 10.1021/la404258v. Epub 2014 Feb 5.
We report here the gelation behavior of two novel L-cysteine-based amphiphiles bearing a poly(ethylene glycol) tail. The amphiphiles were found to form transparent organogels in both apolar and aprotic polar solvents at reasonably low concentrations. In chloroform, dichloromethane, and benzene solvents, the organogels are formed at room temperature without the requirement of heating-cooling cycle due to strong hydrogen-bonding interaction between gelator molecules. The swelling kinetics, however, becomes faster on heating. Unlike most organogels of low-molecular-mass gelators, these organogels do not exhibit a gel-to-sol transition on heating but instead become rigid when heated. Surprisingly, in polar solvents, the gelation required a heating-cooling cycle, and the sol-to-gel transition was found to be reversible. The gelation abilities of the amphiphiles were correlated with the hydrogen-bonding parameters of the solvents. Intermolecular H-bonding interaction was found to be the major driving force for the organogelation. The morphology of the organogels was investigated by the use of optical as well as electron microscopy and was found to be dependent on the nature of solvent. The mechanical strengths of the organogels were studied by rheological measurements.
我们在这里报告了两种新型基于 L-半胱氨酸的两亲分子的胶凝行为，它们带有聚乙二醇（PEG）尾巴。这些两亲分子在相当低的浓度下，在非极性和非质子极性溶剂中都能形成透明的有机凝胶。在氯仿、二氯甲烷和苯溶剂中，由于凝胶分子之间的氢键相互作用较强，有机凝胶在室温下形成，无需加热-冷却循环。然而，在加热时，溶胀动力学会加快。与大多数低分子量凝胶剂的有机凝胶不同，这些有机凝胶在加热时不会发生凝胶到溶胶的转变，而是变得坚硬。令人惊讶的是，在极性溶剂中，凝胶化需要加热-冷却循环，并且发现溶胶到凝胶的转变是可逆的。两亲分子的凝胶能力与溶剂的氢键参数相关。分子间氢键相互作用被认为是有机凝胶形成的主要驱动力。通过使用光学和电子显微镜研究了有机凝胶的形态，发现其形态取决于溶剂的性质。通过流变学测量研究了有机凝胶的机械强度。
