Validation of the COMPASS force field for complex inorganic–organic hybrid polymers

Inorganic–organic hybrid polymers are promising alternatives to simple organic polymers. They combine the advantages of organic and inorganic components in one homogeneous material, which can be adjusted to match sophisticated demands for various possible applications ranging from soft silicones to hard hybrid ceramics. Typically, the inorganic network is formed by a sol-gel reaction whereas the organic network is built by a polymerization reaction. Due to their complex architecture on a molecular level, it is often impossible to experimentally obtain information on the atomistic structures of such hybrid materials. In this work, we validate the all-atom COMPASS force field for the simulation of such materials on the basis of a simplified test system with (methacryloyloxymethyl)dimethylethoxysilane as a precursor; which has only one functionality for inorganic condensation, building only one defined condensation product in the sol-gel reaction. The force field was validated based on the experimentally determined single crystal structure of this condensation product and the calculation of its glass transition and melting temperatures by molecular dynamics. The prediction of fluid densities was validated on liquids of the precursor and the condensation product. The validated force field is applied to demonstrate the influence of inorganic cross-linking in the resulting polymer on a simplified network model.