The possible formation of molecular-complex phases of s-PS with styrene dimers has been investigated by their sorption in amorphous and nanoporous delta-form films. X-ray diffraction, C-13 solid state NMR, and FTIR analyses have shown that only 1,3-diphenylbutane (dpb), but not 1,4-diphenylbutane, forms a highly stable molecular-complex with s-PS. Preliminary structural considerations indicate that this s-PS/dpb molecular-complex phase presents an intercalate structure, with host-monomer-unit/guest stoichiometric ratio of 4/1 and with a guest conformation with anti C2-C3 bond. Guest conformational behavior has allowed to discriminate, for the first time by a NMR technique, between guest molecules located in crystalline and amorphous s-PS phases. Presently dpb is the s-PS guest with maximum volume (approximate to 0.36 nm(3)) and maximum number of non-hydrogen atoms (n = 16).