Organic–inorganic hybrid gels having functionalized silsesquioxanes

Abstract

Hybrid terpolymers consisting of polyhedral oligomeric silsesquioxanes (POSS), N,N-dimethylacrylamide, and bipyridine monomer were synthesized by a common radical polymerization method and their structures and thermal properties were studied by FT-IR, ¹H NMR, DSC, TGA. The thermal stabilities of the hybrid terpolymers increased on increasing the content of POSS in the feed ratio. New hybrid gels containing POSS were prepared through the coordination of various metal ions to 2,2′-bipyridine-modified hybrid terpolymers. Highly concentrated solutions of terpolymers with iron(II) sulfate or ruthenium(III) chloride gave hybrid gels in good yields. On the other hand, no hybrid gel was formed with nickel(II) chloride even at much higher concentrations of nickel ions due to rapid ligand exchange reactions causing the polymer network to disappear as a result of a change in the nature of the coordination bonds from an intermolecular network to an intramolecular network. The degree of swelling and the thermal stability of the gels in various solvents were dependent on the content of POSS moiety in the hybrid gel and the ruthenium gel was considerably more stable than the iron and nickel gels. The hybrid gels containing POSS had properties characteristic of hydrogels as well as those of lipogel depending on the content of POSS in the hybrid gel. By analysis of the degree of swelling, it was concluded that the amount of POSS moiety in the hybrid gel has a significant effect on the degree of swelling in this system.