Département de Chimie Moléculaire, Université Joseph Fourier, CNRS, BP 53, 38041 Grenoble, France.
Langmuir. 2009 Aug 4;25(15):8751-62. doi: 10.1021/la900174e.
The domain of soluble metallopolymers (i.e., polymers spontaneously obtained from the self-assembly of metal ions and polytopic bridging ligands) is promising for the construction of novel materials with perspectives in magnetic, redox, optical, electrochromic, or mechanical properties. We report the preparation and characterization of metallo-supramolecular gels based on a multitopic cyclam bis-terpyridine platform (CHTT) that are representative of a second generation of molecular gels exhibiting "intelligent" properties. The systems were characterized by UV-visible spectroscopy, cyclic voltammetry, viscosimetry, rheology, and small-angle neutron scattering (SANS). A basic analysis of the viscosity taking into account the interplay of hydrodynamic versus Brownian motions of 1D species is proposed. SANS data demonstrate the formation of rod-like species whose radius R and aspect ratio f = L/R were extracted. Rheological features are typical of weak gels having storage moduli of more than 1 order of magnitude weaker than for ordinary molecular organogels. These new molecular materials exhibit interesting properties: (i) chemosensitivity, with the gelation being dependent on the type of metal, stoichiometry M/CHTT, solvent, and counterion; (ii) electro-sensitivity: the Co(II)/CHTT system can be electrochemically and reversibly commuted between the gel (red) and liquid (green) states; and (iii) mechanical sensitivity, with the system being able to cycle from weakly to highly viscous states upon fast application/suppression of a shearing stress.
可溶性金属聚合物（即金属离子和多齿桥联配体自组装自发获得的聚合物）领域在构建具有磁、氧化还原、光学、电致变色或机械性能的新型材料方面具有广阔的前景。我们报告了基于多齿环戊二烯双吡啶平台（CHTT）的金属超分子凝胶的制备和表征，这些凝胶是具有“智能”特性的第二代分子凝胶的代表。通过紫外可见光谱、循环伏安法、粘度、流变学和小角中子散射（SANS）对体系进行了表征。提出了一种基本的粘度分析，考虑了一维物质的流体动力与布朗运动之间的相互作用。SANS 数据表明形成了棒状物质，从中提取了其半径 R 和纵横比 f = L/R。流变学特征是典型的弱凝胶，其储能模量比普通有机分子凝胶弱一个数量级以上。这些新型分子材料表现出有趣的性质：（i）化学敏感性，凝胶化取决于金属的类型、化学计量比 M/CHTT、溶剂和抗衡离子；（ii）电敏感性：Co(II)/CHTT 体系可以在凝胶（红色）和液体（绿色）状态之间进行电化学和可逆转换；（iii）机械敏感性，该体系能够在快速施加/抑制剪切应力时从低粘度状态循环到高粘度状态。
