The formation of a cocrystalline phase of syndiotactic polystyrene (s-PS) presenting layers of benzyl methacrylate (BzMA) guest molecules intercalated with layers of closely packed alternated enantiomorphous polymer chains is presented The distance between these polymer layers, which for the nanoporous delta phase of s-PS is of 1 05 nm increases up to 1 61 nm due to the guest intercalation The proximity of the BzMA molecules in the guest layers makes possible their irradiation Induced polymerization inside the cocrystalline film The polymerization products are expelled from the crystalline host phase and the latter as a consequence of guest exclusion, reorganizes in a lower order helical mesomorphic phase