Thermoresponsive, optically active films based on Diels-Alder chemistry

Reversible Diels-Alder chemistry was exploited to develop polymer films in which a change in optical clarity can be thermally triggered. SiO2 nanoparticles of various sizes were functionalized with maleimido moieties. A furyl-terminated poly(ethylene glycol) linker was prepared and tethered to the SiO2, nanoparticles via a Diels-Alder (DA) linkage. The pegylated SiO2 nanoparticles were randomly distributed within a poly(methyl methacrylate) (PMMA) matrix, resulting in an optically transparent film. Annealing the film cleaves the DA linkage and effectively renders the SiO2 particles immiscible within the PMMA matrix creating a driving force for particle aggregation. The large aggregates were able to scatter light and resulted in an optically opaque film.