We describe the preparation of nanostructured polymeric materials by polymerizing a monomer within a scaffold composed of self-assembled nanofibrils. 1,3:2,4-Dibenzylidene sorbitol (DBS) is an inexpensive sugar derivative that can form nanofibrillar networks in a variety of organic solvents at relatively low concentrations. Here, we induce DBS nanofibrils in styrene and then thermally initiate the free-radical polymerization of the monomer. The polymerization proceeds without any evidence of macroscopic phase separation, ultimately yielding a transparent solid of polystyrene. Within this material, intact DBS nanofibrils (diameter 10-100 nm) are preserved, as shown by atomic force microscopy (AFM). The DBS fibrils can also be subsequently extracted from the polymer, leaving behind a network of nanoscale pores. The porosity of the resulting polymer has been characterized by the BET technique.