PolyHIPE are highly porous, open-pore, cross-linked polymers synthesized within high internal phase emulsions (HIPE). Biodegradable polycaprolactone (PCL) oligomers were incorporated into polyHIPE using two approaches. The first approach involved copolymerization with a vinyl-terminated PCL (PCL-VL). This approach yielded a typical polyHIPE structure with voids on the order of tens of microns. The covalent bonds formed by PCL-VL prevented its removal during emulsifier extraction. The second approach involved the formation of semi-interpenetrating polymer networks (semi-IPN) with a PCL diol (PCL-OL). The relatively hydrophilic PCL-OL destabilized the HIPE and produced voids on the order of hundreds of microns, a size more appropriate for tissue engineering applications. The PCL-OL, which is more mobile than the covalently bound PCL-VL, underwent more extensive phase separation. In addition, a significant amount of PCL-OL was removed during emulsifier extraction. Cells were successfully attached to the surface of a semi-IPN polyHIPE, forming a monolayer. Eventually, spontaneous differentiation of the cells and the formation of myotubes were observed.