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Syndiotactic polystyrene (s-PS) films including a fluorescent guest (naphthalene, NP) in their nanoporous δ crystalline phase have been prepared and characterized by X-ray diffraction, infrared linear dichroism, molecular modeling, and fluorescence depolarization techniques. A nearly perpendicular orientation of the fused rings of NP guest molecules with respect to the chain axis of the δ crystalline structure has been established by molecular mechanics and by evaluation of directions of transition moment vectors of infrared vibrational modes. The fluorescence depolarization is more efficient for NP guest molecules into the host phase than for NP molecules simply absorbed in the amorphous phase. This could be due to a more efficient resonance energy transfer between guest molecules, possibly associated with their ordered positioning and orientation into the host nanoporous polymeric crystallites.

A fluorescence probe technique was used to investigate the role of the solvent in the syndiotactic polystyrene (sPS) thermoreversible gel system. Four probe molecules with different molecular sizes were dispersed throughout the gels, and their fluorescence anisotropy values were examined in detail for a range of sPS concentrations. The results showed that solvent molecules are mobile in the area where solvent gathers in the gels and that, in sPS/chloroform gels consisting of 2 1-helical sPS chains forming a polymer-solvent molecular compound with chloroform, there exists a distribution of free volume in an area where the sPS chains associate and into which molecules smaller than 1,5-dimethylnaphthalene are able to penetrate. The size of the free volume between the sPS chains is consistent with that of the cavity size in the δ-empty crystalline form of sPS solids. However, in the sPS/trans-decalin gels having a spherulitic morphology, almost all NP molecules were assumed to be excluded out of the clathrate δ crystalline form not due to their cavity size but rather due to the growing process of the solvated crystalline forms.

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The morphology of syndiotactic polystyrene (SPS) with several typical fragrant molecules is studied to clarify what solvent conditions can produce SPS gel, which is expected to be a material that can release fragrance for a long period of time. Eight fragrant solvent molecules are employed to dissolve SPS at high temperatures and the morphologies they show after cooling are checked. Their morphologies can be divided into three: a gel with a three‐dimensional network consisting of a fibrillar structure having the SPS δ phase, a paste‐like state consisting of a non‐lamellar spherulitic structure having the SPS γ phase, and a sherbet‐like state consisting of a lamellar structure having the SPS β phase. Finally, the necessary conditions of a solvent to be able to form an SPS gel turn out to be its molecular size being less than ≈160 Å3 and its Fedors' solubility parameter having a value whose gap from SPS is less than 1.5 (cal/cm3)1/2.magnified image

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