Light-sensitive resins are commonly used materials in additive manufacturing (AM) processes. Vat photopolymerization is an AM technique that relies on the local solidification of a liquid photopolymer resin by light exposure, forming desired 3D objects in a layer-by-layer manner. Digital light processing (DLP) 3D printing is a type of vat photopolymerization that provides an innovative strategy for producing 3D objects with high resolution, as well as high dimensional accuracy, from versatile feedstock materials. Although the DLP technology offers layer-free, scalable, and rapid production of 3D objects, it is still often limited to a single material. However, multi-functional materials may bring revolutionary solutions in a variety of fields, encompassing soft robotics, electronics, and biomedical engineering. Multi-material vat polymerization brings many challenges, including printing a single photocurable resin where heterogeneous properties of materials can be spatially controlled, forming complex geometries with embedded functionality. In this dissertation, orthogonal photochemistries undergoing independent cross-linking reactions using light with different wavelengths were explored, optimized, and studied in detail. A dual photocurable resin based on commercially available monomers was developed, which consisted of multi-functional acrylates (cured at 405 nm by radical-induced chain growth reaction) and bi-functional epoxy-monomers (additionally cured at 365 nm by cationic curing). Furthermore, the synthetic route for bio-based acrylate-modified polyester resin was optimized with sufficiently low viscosity for processing them with vat photopolymerization 3D printing. In the final part of the thesis, DLP 3D printing of functional polymers was demonstrated by printing magneto-responsive thiol-acrylate composites. Thermo-activated bond exchange reactions were exploited by following catalyzed transesterification to induce a material flow above the networks' topological freezing temperature. The magneto-responsive photocurable resin was optimized in terms of viscosity and stability. Magneto-active objects were printed with a Fe3O4 loading up to 6 wt%.