Confined polymerization in silica nanoporous sol-gel glasses

Confining soft matter in dimensions of a few molecular diameters impacts its physical properties, compared to its bulk counterpart. As spatial constraints approach the range of intermolecular interactions, or even the size of the molecular entities, confined materials can show dramatic changes in their structural and thermodynamical properties, which in turn can affect the rate of chemical reactions and phase transitions. In this light, polymerization dynamics are expected to change under nanoconfinement, opening new pathways for studying fundamental physical and chemical phenomena. Ηere we report on the effect of spatial confinement on free radical photopolymerization. We used monolithic silica glasses prepared by the sol-gel method as the means of confinement, with pore sizes ranging between 2 and 10 nm. Our findings showed a dramatic enhancement of the polymerization efficiency under nanoconfinement, with the rate of polymerization increasing as the spatial confinement becomes tighter. The origin of this effect will be discussed in terms of the polymerization kinetics of free radical polymerization.