Christopher W. Allen

Inorganic and Polymer Chemistry

Research-Active Emeritus Professor

Christopher.Allen@uvm.edu
phone: 802-656-0193
office: Cook Rm A131

The research program in my group is devoted to the study of inorganic rings and polymers. The inorganic ring chemistry presents interesting questions of electronic structure, reactivity and mechanism. Additionally, these ring systems may be transformed into hybrid inorganic-organic polymers which are new classes of materials with interesting properties having applications such as flame retardant, polymeric electron transfer or as membranes.

Monomers of interest are derived from main-group ring or linear systems which often exhibit some formal degree of multiple bonding, e. g., phosphazenes, (X₂P=N)_n or borazines (XBNR)₃. Ring-opening polymerization or condensation of linear species leads to polymers with inorganic backbones, which can undergo further substitution reactions to produce novel materials. Alternatively, substitution reactions on the inorganic monomers are conducted in order to add an organic functionality, such as an olefin. Polymerization of the olefin in these derivatives leads to linear, hyperbranched and crosslinked polymers with inorganic substituent. Studies of relative reactivities of various of these monomers in copolymerization reactions give valuable insight into the polymerization mechanism and the perturbation of the electronic structure of the olefin by the inorganic substituent. We are interested in how incorporation of the inorganic entity modifies polymer structure, reactivity and properties. An active component of our synthetic studies involves synthesis of organometallic derivatives of the parent polymers and their applications in biosensors. Characterization studies of these systems include kinetics, computational methods, electrochemistry, and spectroscopy with a particular emphasis on NMR (³¹P, ¹⁹F, ¹³C, ¹H) including 2-D methods and simulation of complex spin systems. A wide array of polymer characterization techniques is also employed.

Selected Publications

Myer,C.N.; C.W.Allen, C.W. "Copolymerization of Chlorocyclotriphosphazene Derivatives Containing the Methacyclylbutenedioxy and N-(Ferrocenylmethylamino) Substituents', J. Inorg. Organomet. Polym.Materials, 2007,17,143.

Calichman, M; Derecskei-Kovacs,A. ; Allen,C.W. "The Origin of Endocyclic Bond Length Variations in Disubstituted Cyclotriphosphazenes", Inorg.Chem.,2007,46, 2011.

Allen,C.W., "From Rings to Polymers", J.Inorg. Organomet. Polym. Mater., 2007,17, 341.

Hagberg, E.C.; Hart, M.W.;Cong, L.;Allen,C,W.; Carter,K.R. "Cyclophosphazene Containing Polymers as Imprint Lithography Resists" J.Inorg. Organomet. Polym. Mater.,2007, 17, 377.

Cong, L.C.; Allen, C.W. "New Polymers Derived from Multifunctional Cyclo- and Polyphosphazenes," Polymer Materials: Sciernce and Engineering Preprints, 2005, 93 783.

Freund, A. S.; Calichman, M.; Allen, C. W. "The Reactions of Hexafluorocyclotriphosphazene with Sodium Phenoxide," Z. Anorg. Allgem. Chem., 2004, 630, 2059.

Allen, C. W.; Hernandez-Rubio, D. "The Use of Phosphazenes as Flame Retardants" in Phosphazenes: A Worldwide Insight", Vol. II: Applicative Aspects of Polyorganophosphazenes, Gleria, M.; DeJaeger, R. Eds., Nova Science, NY, 2004, Chapter 20, 485.