In recent years self-assembled, organic supramolecular or colloidal arrays have been used as templates for the design of a wide range of novel nanostructured porous materials, using sol-gel chemistry. Herein, mesoporous silica and organosilica films, and colloidal crystal (opal) films, have been synthesized, and various mechanical and dielectric properties investigated.

A series of spin-coated mesoporous silica films were synthesized using a surfactant template, using evaporation-induced self-assembly (EISA). The porosity was controlled by the surfactant/silica molar ratio, thermally-induced collapse at 300-900°C, and deposition within the channels. The Young’s modulus (E) and hardness (H) were measured using nanoindentation, and the results have been compared with conventional models for porous materials. A series of molecular mechanics atomic models of mesoporous silica were used to simulate the elastic and plastic deformation as a function of pore diameter.

Highly-ordered, periodic mesoporous organosilica (PMO) thin films were synthesized from bridged silsesquioxane precursors of the type (EtO)₃SiRSi(OEt)₃ (where R is an organic group), and a novel three-ring [(EtO)₂Si(CH₂)]₃ precursor. Detailed structural characterization has been performed using PXRD, SAXS, SEM, and TEM. PMO films may have important applications as low dielectric constant (k) materials in microelectronics. Capacitance measurements showed that k decreased with organic content to ~ 1.8. A novel ‘self-hydrophobization’ behaviour has been demonstrated, using a bridge-terminal transformation of the organic groups at 400-550°C, to lower k and make the films highly resistant to moisture adsorption. A series of novel dendrimer and ‘semi-dendrimer’ PMO thin films have been synthesized using cationic and block copolymer templates, to further increase the organic content. As a result, the number of organic bridges attached to each Si is increased as a series, from 0 to 4.

Finally, chemical vapour deposition (CVD) was used to sinter silica opal films to systematically control the optical Bragg diffraction and the structural connectivity. SiCl4 and Si(OMe) 4 vapour were used to deposit silica layers to grow necks between silica spheres. Nanoindentation was used to measure E and H as a function of the silica deposition.