Photosciences and Photonics Group, Chemical Sciences and Technology Division, National Institute for Interdisciplinary Science and Technology, CSIR, Thiruvanthapuram-695019, India.
Chem Asian J. 2012 Sep;7(9):2061-7. doi: 10.1002/asia.201200410. Epub 2012 Jun 29.
Linear π-conjugated oligomers are known to form organogels through noncovalent interactions. Herein, we report the effect of π-repeat units on the gelation and morphological properties of three different oligo(p-phenylene-ethynylene)s: OPE3, OPE5, and OPE7. All of these molecules form fluorescent gels in nonpolar solvents at low critical gel concentrations, thereby resulting in a blue gel for OPE3, a green gel for OPE5, and a greenish yellow gel for OPE7. The molecule-molecule and molecule-substrate interactions in these OPEs are strongly influenced by the conjugation length of the molecules. Silicon wafer suppresses substrate-molecule interactions whereas a mica surface facilitates such interactions. At lower concentrations, OPE3 formed vesicular assemblies and OPE5 gave entangled fibers, whereas OPE7 resulted in spiral assemblies on a mica surface. At higher concentrations, OPE3 and OPE5 resulted in super-bundles of fibers and flowerlike short-fiber agglomerates when different conditions were applied. The number of polymorphic structures increases on increasing the conjugation length, as seen in the case of OPE7 with n=5, which resulted in a variety of exotic structures, the formation of which could be controlled by varying the substrate, concentration, and humidity.
线性π共轭寡聚物通过非共价相互作用形成有机凝胶。在此，我们报告了π重复单元对三种不同的寡聚（对苯乙炔）：OPE3、OPE5 和 OPE7 的凝胶化和形态特性的影响。所有这些分子在低临界凝胶浓度下在非极性溶剂中形成荧光凝胶，从而使 OPE3 形成蓝色凝胶，OPE5 形成绿色凝胶，OPE7 形成绿黄色凝胶。这些 OPE 中的分子-分子和分子-基底相互作用强烈受分子的共轭长度影响。硅晶片抑制基底-分子相互作用，而云母表面促进这种相互作用。在较低浓度下，OPE3 形成囊泡组装体，OPE5 形成缠结纤维，而 OPE7 在云母表面形成螺旋组装体。在较高浓度下，OPE3 和 OPE5 在施加不同条件时导致纤维的超束和花状短纤维聚集体。随着共轭长度的增加，多晶型结构的数量增加，如 OPE7 中的 n=5 情况，导致形成了各种奇异结构，其形成可以通过改变基底、浓度和湿度来控制。
