The formation of syndiotactic polystyrene (sPS) intercalates in a series of solvent derived from naphthalene, namely naphthalene, 1,2,3,4-tetrahydro naphthalene (tetralin), and trans-decahydronaphthalene (trans-decalin) has been investigated. For each systems, the temperature-concentration phase diagrams have been established by DSC, the morphology has been observed by optical and electron microscopy, and the molecular structure has been determined by time-resolved X-ray diffraction and neutron diffraction. The morphology depends on the solvent used: in naphthalene and tetralin fibrillar arrays are observed as opposed to assemblies of spherulites in trans-decalin. This morphology might be related to the nature of the intercalates formed: congruently melting in naphthalene and tetralin; incongruently melting in trans-decalin. The time-resolved X-ray and the neutron diffraction investigations are in agreement with the outcomes from the temperature-concentration phase diagrams.