Mixed‐macromer networks prepared by using biodegradable functionalized oligomers and a combinatorial chemistry approach have shown to be networks with high water uptake, excellent mechanical properties, and good cell adhesion. This may be due to phase separation within these networks, although this has not been investigated to date. Here we show that these networks are indeed phase‐separated. In differential scanning calorimetry experiments, Tg values of each constituent material used in the networks were observed. Furthermore, atomic force microscopy and X‐ray diffraction experiments showed phase separation of the crystalline and amorphous phases of the networks in the dry state. In the hydrated state, however, the crystalline phase was not visible. Subsequently, we prepared designed porous 3D structures of the mixed‐macromer networks by using stereolithography. We have shown that such structures have excellent mechanical properties with compression moduli of 20–170 kPa. Unlike conventional synthetic hydrogels such as poly(ethylene glycol) hydrogels, these structures do not fail under compression and return to their original dimensions after re‐equilibration in water. This make these materials excellent candidates for soft tissue engineering of tissues such as menisci or intervertebral discs. Finally, a designed porous meniscus implant was prepared. Copyright © 2016 John Wiley & Sons, Ltd.