Hydrogel microparticles with entrapped liquid are used as the porogen to reproducibly form interconnected pore networks in a porous scaffold. In one embodiment, a biodegradable unsaturated polymer, a crosslinking agent, and a porogen comprising biodegradable hydrogel microparticles are mixed together and allowed to form a porous scaffold in an mold or in a body cavity. Example biodegradable unsaturated polymers include poly(propylene fumarate) and poly(e-caprolactone-fumarate). The cosslinking agent may be a free radical initiator, or may include a free radical initiator and a monomer capable of addition polymerization. Example hydrogel microparticles include uncrosslinked or crosslinked collagen , an uncrosslinked or crosslinked collagen derivative, and an uncrosslinked or crosslinked synthetic biodegradable polymer such as oligo(poly(ethylene glycol) fumarate).