Mesostructured inorganic films from self-assembled templates: Control of morphology from the molecular to the macroscopic scale.

摘要

The use of self-assembling templates is a powerful and convenient route for the preparation of thin films of mesoporous and mesostructured inorganic materials. To achieve templated inorganic films with desirable material properties however, it is generally important to exercise control over their structures not only on the mesoscopic scale, but on the molecular and macroscopic scales as well. Here, we have investigated methods for controlling morphologies over all three regimes of length-scale. We have found that a careful consideration of the thermodynamic phase behavior of the templating species affords excellent control over the mesoscopic morphology of the resulting inorganic films. This approach allowed the production of thin films of mesostructured silica with bicontinuous cubic structures by evaporation-induced self-assembly, which had previously not been accomplished. Towards improving control over the macroscopic properties of mesostructured thin films, we have developed a technique for converting pre-organized block copolymer templates into mesostructured silica and titania replicas. This approach is anticipated to allow pre-processing of the block copolymer film to control the orientation, long-range ordering, and surface patterning of the mesostructure, which will then be preserved upon conversion to a mesostructured inorganic film. On the molecular scale, we have investigated the registry between a molecularly ordered silica framework and the head-group of the surfactant used to template the material. By better understanding the interaction between the surfactant and the molecularly-ordered silicate we hope to understand, and ultimately control, the mechanism by which the surfactant head-group is able to induce formation of a particular crystalline polymorph in the inorganic framework.