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

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.