设计合成了一种缺电性的刚性棒状超分子单体,在葫芦脲(CB[8])存在下,它与富电性的柔性单体受CB[8]包结增强的供体-受体作用驱动在水中共组装形成“刚.柔”(rod-coil)型超分子共聚物.运用核磁共振滴定实验、紫外-可见光谱、二维扩散排序核磁共振谱(DOSY)、动态光散射(DLS)以及透射电子显微镜(TEM)等对超分子聚合物的形成及其结构进行了证实和表征,并发现该超分子共聚物在低浓度下采取伸展的线形构象,当浓度增加到一定程度后其线形骨架发生卷曲,转变为颗粒状团聚结构.
Compared to traditional polymers, supramolecular polymers have quite limited structural diversity. In this context, to develop supramolecular polymers with novel backbone structures is highly desired, since this extends not only the diversity of supramolecular polymers, but also might bring in new functions and applications. In this contribution, a rigid rod-like supramolecular monomer, in which electron-deficient viologen units are incorporated at both ends of its skeleton, was designed and synthesized. Its co-assembly with an electron-rich flexible monomer leads to the formation of a rod-coil supramolecular copolymer, driven by cucurbit[8]uril (CB[8])-encapsulation-enhanced donor-acceptor interaction between naphthol segments of the flexible monomer and viologen units of the rigid monomer. The as-prepared supramolecular polymer was systematically characterized by 1H-NMR analysis, UV-Vis spectroscopy, diffusion-ordered NMR spectroscopy (DOSY), dynamic light scattering (DLS) and transmission electron microscopy (TEM). While the 1H-NMR result indicated host-guest complexation through the encapsulation of a viologen unit and a naphthol segment in the cavity of one CB[8], the existence of donor-acceptor interaction between the two guest molecules was clearly evidenced by UV-Vis spectrum which exhibited a notable charge-transfer absorption in visible region. The formation of large size supramolecular entities in water was revealed by DOSY and DLS studies. And their linearly polymeric backbones were directly observed by TEM. Based on these experimental results, the polymeric structures of the assembled material were confirmed. Furthermore, DLS and TEM investigations also revealed that the supramolecular polymer adopted an extended linear conformation at low concentration, which further curled into aggregated morphology at high concentration. This might be attributed to the tendency of the supramolecular polymer to decrease its surface energy with increasing concentration. The supramolecular copolymer r