β-Cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) formed inclusion complexes with poly(dimethylsiloxane)s (PDMS) of various molecular weights to give crystalline compounds. However, α-cyclodextrin (α-CD) did not form complexes with PDMS of any molecular weight. The yields of the β-CD−PDMS inclusion complexes decreased with increasing molecular weight of PDMS. In contrast, the yields of the γ-CD−PDMS inclusion complexes increased with increasing molecular weight, reached a maximum at molecular weight of around 760, and gradually decreased at higher molecular weight. The chain-length selectivity is reversed between β-CD and γ-CD. The β-CD−PDMS inclusion complexes are stoichiometric 1:1 compounds when the molecular weights of PDMS are low. The γ-CD−PDMS inclusion complexes are stoichiometric 2:3 (cyclodextrin:monomer unit of PDMS) compounds. The complexes were isolated and characterized by 1H NMR, 13C CP/MAS NMR, and X-ray diffraction studies. The inclusion modes are discussed.

β-Cyclodextrin (β-CD) and γ-cyclodextrin (γ-CD) formed inclusion complexes with poly(dimethylsilane)s (PSi) of various molecular weights to give crystalline compounds. However, α-cyclodextrin (α-CD) did not form complexes with PSi of any molecular weight. The yields of the β-CD−PSi inclusion complexes decreased with increasing molecular weight of PSi. In contrast, the yields of the γ-CD−PSi inclusion complexes increased with increasing molecular weight, reached a maximum at molecular weight of around 760, and gradually decreased at higher molecular weight. The chain-length selectivities are totally different between β-CD and γ-CD. The γ-CD−PSi inclusion complexes are stoichiometric 1:3 (γ-cyclodextrin:monomer unit of PS) compounds. The complexes were isolated and characterized by 1H NMR, 13C CP/MAS NMR, and X-ray diffraction studies. These results suggest that CDs form channel-type complexes with PSi. The optical properties were studied by ultraviolet absorption and fluorescence spectroscopy. The PSi main chain in the cavities of γ-CD takes an all-trans conformation.

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