In this study, the unsymmetrical Ï-conjugated gelators, 2-(3,4-bis(alkoxy)phenyl)-5-(pyridine-4-yl)-1,3,4-oxadiazole [4-POXD-Bn (n = 4, 8, 12)], were synthesized and screened for gelation in various solvents. The tendencies of the critical gelation concentration (CGC) and the gelâsol phase transition temperatures (Tgel) of the 4-POXD-B8 gels, as well as the relationship between the end-chain length of gelator and gelation ability, indicated that the solvophobic effect has a critical role in gelation. For the specific gelator that we studied, we observed that the strength of the solvophobic force was related to the solvent properties. The solvent effect on gelation was studied quantitatively using the solvent polarity parameters: polar solubility parameter (δa), dielectric constant (ε), and polarity parameter (ET(30)). The results revealed that the favorable δa domain and ET(30) domain for the gelation of 4-POXD-B8 was in the range of 8.1â12.6 (cal cmâ3)1/2 and 43.3â55.7 kcal molâ1, respectively. Meanwhile, a decrease of δa and ET(30) in the solvents is unfavorable for gelation. Furthermore, the solvent effect on the microstructure of the gels was studied via scanning electron microscopy (SEM). The SEM images revealed that the gels from 4-POXD-B8 in DMSO and DMF were composed of helical ribbons, whereas those formed in other solvents consisted of flat ribbons.
在这项研究中,我们合成并筛选了非对称Β-共轭凝胶剂2-(3,4-双(烷氧基)苯基)-5-(
吡啶-4-基)-1,3,4-恶二唑[4-POXD-Bn (n = 4, 8, 12)]在各种溶剂中的凝胶化性能。4-POXD-B8凝胶的临界凝胶浓度(CGC)和凝胶-溶液相变温度(Tgel)的趋势以及凝胶剂端链长度与凝胶化能力之间的关系表明,疏溶剂效应在凝胶化过程中起着关键作用。对于我们所研究的特定凝胶剂,我们观察到疏溶剂力的强度与溶剂性质有关。我们使用溶剂极性参数:极性溶解度参数(Δa)、介电常数(µ)和极性参数(ET(30))对溶剂对凝胶化的影响进行了定量研究。结果表明,4-POXD-B8凝胶化的有利Δa域和ET(30)域分别在8.1-12.6 (cal cm-3)1/2和43.3-55.7 kcal mol-1的范围内。同时,溶剂中Δa和ET(30)的降低不利于凝胶化。此外,我们通过扫描电子显微镜(
SEM)研究了溶剂对凝胶微观结构的影响。
SEM图像显示,4-