Antagonistic Two-Color Control of Polymer Network Formation

Offering high spatiotemporal resolution, dual wavelength-controlled soft matter network formation paves the way to advanced printing techniques with optimized performance. One of the most promising approaches is the antagonistic control of covalent bond-forming reactions with two colors of light, where photoexcitation with one wavelength induces a photochemical reaction, while irradiation with the other ceases it in the presence of the first color. Herein, we combine a photoactivatable diene precursor and a photoswitchable dienophile, establishing a dual-wavelength-gated cycloaddition reaction capable of controlling polymer crosslinking. Upon incorporation of the diene precursor into a methacrylate copolymer and the synthesis of a difunctional dienophile cross-linker, selective polymer network formation is promoted under sole UV illumination, while it can be efficiently suppressed with simultaneous redlight irradiation. Critically, the methodology is used for the preparation of solid polymer materials with antagonistic two-color control of their cross-linking status, ultimately allowing the fabrication of spatially patterned polymer films.