Auto-organization of nanostructured organic–inorganic hybrid xerogels prepared from planar precursors by sol–gel processing
作者:Geneviève Cerveau、Robert J. P. Corriu、Eric Framery、Frédéric Lerouge
DOI:10.1039/b405008h
日期:——
Nanostructured hybrid materials were prepared by solâgel hydrolysis-polycondensation of 1,3,5-tris(p-triethoxysilylphenyl)benzene PR having a rigid structure and 1,3,5-tris(p-trimethoxysilylpropylphenyl)benzene PF having a planar core connected to three short and flexible arms. Both precursors presented nine directions for solid formation. Their organization was evaluated by birefringence measurements (micrometre scale) and X-ray diffraction studies (nanometre scale). The influence of the planar geometry and the rigidity or flexibility of the organic groups has been studied as well as the effect of changes in experimental conditions. It has been shown that the organization of these solids was less influenced by the experimental parameters than in the case of linear precursors. In the case of the rigid precursor PR, the solids obtained XR had a high intensity of birefringence (7.5â8 Ã 10â3) and the gels presented cracks whatever the experimental conditions (nucleophile or acid catalysis). In contrast the flexible precursor PF led to solids XF with a lower birefringence (6.2â6.8 Ã 10â3) and the morphology of the solids in the cells depended on the concentration of catalyst. Interestingly the birefringence appeared without cracks with a lower amount of catalyst and isotropic circular cross-shaped nodules were observed in this case whatever the temperature. The X-ray diffraction diagrams clearly showed that these solids presented a better nanometre scale organization than the gel formed from 1,3,5-tris(trimethoxysilyl)benzene. These observations show that the auto-organization of hybrid materials appears induced by weak van der Waals type interactions as a general phenomenon which is not limited to linear and mesogenic precursors.
通过水解-缩聚反应制备了具有刚性结构的1,3,5-三(对-三乙氧基硅烷基苯基)苯PR和具有平面核与三个短而灵活臂连接的1,3,5-三(对-三甲氧基硅烷基丙基苯基)苯PF的纳米结构杂化材料。两种前驱体均表现出九个固态形成方向。通过双折射测量(微米尺度)和X射线衍射研究(纳米尺度)评估它们的组织结构。研究了平面几何形状、有机基团的刚性或柔韧性对组织的影响以及实验条件变化的影响。结果表明,与线性前驱体相比,这些固体的组织受实验参数的影响较小。对于刚性前驱体PR,获得的固态XR具有高双折射强度(7.5-8×10^-3),无论实验条件如何(亲核或酸性催化),凝胶均出现裂纹。相比之下,弹性前驱体PF得到的固态XF的双折射较低(6.2-6.8×10^-3),固体在细胞中的形态取决于催化剂的浓度。有趣的是,在较少催化剂的情况下,双折射出现无裂纹,并且在此情况下无论温度如何,均观察到各向同性的圆环形十字结节。X射线衍射图谱清楚地显示,这些固体比由1,3,5-三(三甲氧基硅烷基)苯形成的凝胶具有更好的纳米尺度组织结构。这些观察表明,杂化材料的自组装现象是由弱范德华型相互作用诱导的普遍现象,不仅限于线性和介晶前驱体。