Electronic structure and reaction mechanism as guides to the design of hybrid inorganic–organic polymers

Systematic approaches to the design of organofunctional cyclophosphazene monomers and their conversion to organic backbone polymers with cyclophosphazene substituents are described. A variety of methods including DFT calculations, photoelectron spectroscopy and copolymerization reactivity ratios show that the π electrons in an olefin attached to a cyclophosphazene undergo σ polarization towards the phosphazene. This effect may be mediated by electron donors on the olefin or, more effectively, by an insulating function between the olefin and the inorganic ring. Two optimized monomers, P3N3Cl5OR (RC6H4CHCH2, (CH2)4OC (O)CMeCH2), have been prepared and their homo- and copolymerization behavior explored. Mixed phosphazene substituent systems have also been developed. Per substituted monomers, P3N3(OR)6, have been developed and converted to cross linked, hyperbranched and cyclomatrix materials via multi arm polymerization.

Examination of monomer electronic structure and the mechanism of synthesis lead to two optimized monomers, P3N3Cl5OR (RC6H4CHCH2, (CH2)4OC-(O)CMeCH2), for hybrid inorganic–organic polymers. Homo- and copolymerization behavior of these as well as mixed substituent and multiarmed monomers have been explored.Figure optionsDownload as PowerPoint slideHighlights
► Phosphazenes interact with olefins by a σ polarization mechanism.
► Polymerization of organofunctional aryl and alkyloxyphosphazenes occurs.
► Optimal monomers contain p-vinylphenoxy or oxybutyl methacrylate groups.
► Multiply substituted phosphazenes give cross-linked and hyperbrached polymers.