Polymer foams are utilized in a range of applications such as absorption, mechanical cushioning, thermal and sound insulation, and medical devices. In comparison with amorphous polymer foams, foams of semicrystalline polymers are desirable in applications that require higher service temperatures and chemical resistance, but preparing foams of semicrystalline polymers is challenging due to their weak melt strength near processing temperatures. Blending of immiscible polymers has emerged as a convenient route to tune the viscoelastic and crystallization properties of polymers. Here we show that the in-situ generation of a fibrillar morphology during physical blending of immiscible polymers can broaden the foam processing window of semicrystalline polymers. These results formed the basis for a W.O. Patent. We anticipate that these results will help in the development of alternative polymer formulations and optimization of existing ones for the large-scale manufacture of semicrystalline polymer foams with unique properties for advanced applications. For example, novel superhydrophobic and oleophilic open-cell foams were obtained from polypropylene (PP) containing polytetrafluoroethylene (PTFE) fibrillar dispersed phases in a fully scalable extrusion process. These open-cell foams are technologically promising for applications such as oil-spill cleanup, organic pollutant removal, and field water remediation.