Mesoporous polymer-silica nanocomposites with stimuli responsive functional groups

Mesoporous composites based on poly(chloromethylstyrene) (PCMS) and poly(glycidyl methacrylate) (PGMA) polymers combined with large pore silica (SBA-15) are presented. These highly porous mesostructured polymerSBA-15 composites containing azobenzene functionalities have been synthesized based on the free-radical polymerization technique by using chloromethylstyrene or glycidyl methacrylate monomers. Photo- and pH-triggered isomerization of azobenzene groups was demonstrated in the solid phase for various synthesized composites. The exposure of all materials to acid vapors causes a color change to deep red, whereas the exposure to base turns the composites to light yellow. Moreover, contact with acid vapors leads to significant decrease in the mesopore size, as revealed by nitrogen at 77 K physisorption experiments. In contrast, basic treatment prompts reversion to the original pore size. Changes occurring upon acid or base treatments can be explained by the trans-cis isomerization phenomenon, as demonstrated by the UV-vis spectroscopy.