Gel Point Determination of TEOS-Based Polymeric Materials with Application on Conservation of Cultural Heritage Buildings

Here we present measurements on the gel time of inorganic-organic materials used for stone preservation by means of rheology and dynamic light scattering. Our hybrid material is composed of tetraethyl orthosilicate (TEOS) and polydimethylsiloxane (PDMS) using a nonionic surfactant (n-octylamine) as a template. Moreover, zinc oxide (ZnO) nanoparticles are dispersed in the medium with the aim of obtaining a nanocomposite with potential biocide properties. In our case, we use the ZnO particles as tracers to infer from their scattered intensity mechanical information of the suspending medium. We have found that dynamic light scattering experiments provide similar information on the gelling time, about 30 hours, to that obtained from rotational rheology and oscillatory rheology. This result confirms the validity of light scattering, which is a noninvasive technique, to characterize mechanical properties of time evolving hybrid materials through nonperturbative and well-controlled experiments.