Introduction. In general, our current research involves the synthesis of new compounds and the development of new synthetic methods in several areas of main group element chemistry. We are especially interested in the synthesis and characterization of new polymeric materials based on such chemistry. In comparison to conventional polymers, many of these new systems have novel physical, thermal, surface, optical, or electrical properties and, hence, potential applications in a variety of areas of high technology. The study of these novel polymers and their small-molecule precursors provides a broad range of challenging problems to the synthetic chemist. Extensive use is made of modern instrumentation including multinuclear (¹H, ¹³C, ³¹P, ¹⁹F ²⁹Si, ¹¹B) and 2-D NMR spectroscopy, Size Exclusion Chromatography, Differential Scanning Calorimetry, and Thermal Gravimetric Analysis. Three of our ongoing projects are summarized below.

Poly(alkyl/arylphosphazenes). This project involves detailed studies of the synthesis, characterization, and reactivity of new polyphosphazenes, [R₂PN]_n, bearing only P-C bonded substituents along the polymer backbone.

Recent results, using the condensation polymerization of suitably constructed Si-N-P compounds, include the preparation of the first fully alkyl/aryl substituted polyphosphazenes, some moderately cross-linked poly(alkyl/aryl-phosphazenes), polymers with pendant phosphine, silane, vinyl, or fluorocarbon groups, and a few with transition metal centers attached through phosphine ligands. Some of our current investigations are aimed at the synthesis of polyphosphazenes and Si-N-P compounds with more diverse organic and inorganic functional groups. The condensation polymerization process itself and the electronic and steric factors which influence it are also being studied in greater detail. New catalysts/initiators for the polymerization process are also being developed.

Boron-Nitrogen Prepolymers. Our research in this area is concerned with the synthesis, structure, and reactivity of new compounds containing Si-N-B, B-N-B, or B-N-P linkages. Interest in the Si-N-B compounds, in particular, stems from their novel bonding and stereochemical features which are due to the influence of the p-acceptor ability and steric bulk of the silyl groups on the nitrogen-boron bond.

Moreover, the high susceptibility of silicon to nucleophilic attack often makes these compounds useful as synthetic reagents via desilylation processes. At present, the reactivity of several types of small-molecule B-N compounds is being exploited in the development of condensation reactions for the preparation of new B-N polymers and/or oligomers. These compounds, in turn, may prove to be important precursors to boron nitride ceramic fibers and other solid state materials.

Fluorocarbon-Inorganic Hybrid Polymer Systems. In a collaborative effort with Dow Chemical, we are exploring the diverse preparative chemistry of new trifluorovinyl ether (TFVE) derivatives of many phosphorus, silicon, and boron containing systems.

Thermolysis of these TFVE monomers readily affords a wide variety of novel perfluorocyclobutane (PFCB) polymers via a cyclodimerization polymerization process. The incorporation of PFCB units into the polymer backbone or as crosslink sites leads to new Teflon-like materials with useful properties such as low dielectric constants and high thermal stability. The properties of such systems can be easily tailored by chemical modification of the spacer groups.

Selected Publications (Complete List)

Neilson, R. H.; Wang, B.  "Synthesis of Some 4-Aryl Substituted Poly(alkyl/aryl-phosphazenes)"  J. Inorg. Organomet. Polym. 2007, 17, 407-412.

Neilson, R. H.; Devulapalli, P.; Jackson, B. K.; Neilson, A. R.; Parveen, S.; Wang, B.  "Synthesis and Reactivity of (Silylamino)- and (Silylanilino)phosphines"  ACS Symposium Series 2006, 917, 325-334.

Longlet, J. J.; Bodige; S. G.; Watson, W. H.; Neilson, R. H.  "Synthesis, Structure, and Reactivity of Some N-Phosphorylphosphoranimines" Inorg. Chem. 2002, 41, 6507.

"(p-Trifluorovinyloxy)phenyllithium: Formation, Synthetic Utility, and Theoretical Support for a Versatile New Reagent in Fluoropolymer Chemistry" Ji, J.; Narayan-Sarathy, S.; Neilson, R. H.; Oxley, J. D.; Babb, D.A.; Rondan, N. G.; Smith, D. W., Jr. Organometallics 1998, 17, 783.