Photoactivated Structurally Tailored and Engineered Macromolecular (STEM) gels as precursors for materials with spatially differentiated mechanical properties

- Structurally Tailored and Engineered Macromolecular (STEM) gel networks synthesized.
- Post-synthesis modification of gels through secondary polymerization from incorporated photo-initiator sites demonstrated.
- Spatial differentiation of mechanical properties achieved by UV-irradiation through masks of different opacity.
- Stiffness of resulting materials increased with the number of photons per initiation site.

The concept of a Structurally Tailored and Engineered Macromolecular gel (STEM gel) is presented. A STEM gel is comprised of a network with latent initiating sites allowing for the post-synthesis, spatially specific modification of the matrix. A direct synthetic method was employed and photo-active STEM gels based on (meth)acrylates were synthesized by free radical copolymerization of different monomers, a crosslinker, and a photo-active dormant initiator/monomer (inimer) based on the radical photoinitiator 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone (Irgacure 2959). Infiltration by a solution of a crosslinker was followed by the UV triggered polymerization of secondary polymeric chains. Irradiation through masks with different transmittance resulted in materials with spatially differentiated mechanical properties.

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