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Thieo E. Hogen-Esch

  
Professor of Chemistry

Research Focus

 

Polymer synthesis using anionic, radical and other controlled polymerization methods Physical Properties of Polymer Rings Macrocyclic vinylaromatic polymers and copolymers synthesized by anionic polymerization followed by high dilution intramolecular coupling show properties that are distinctly different from linear polymers of the same length. For instance cyclic poly(2-vinyl fluorene), poly(2-vinylnaphthalene) and similar polymers or copolymers show a fluorescence that is enhanced by up to 200 percent. compared to the linear polymers of the same length. Very rapid intramolecular chromophore-to-chromophore Förster energy transfer (~1 ps) has been demonstrated in some of these polymers that have potential for light harvesting applications and this is being explored in collaboration with the Bradforth group. Self-Assembling Light Emitting Polymer Systems Block copolymers frequently show spatially ordered domain formation by thermodynamically driven phase separation of polymer block at the nanoscale level (10-200 nm). The resulting physical crosslinking of chains is of interest, for instance, in thermoplastic elastomers and in electro-optic and other applications. For instance we have synthesized perfluorocarbon (RF) containing self-assembling polymers containing vinylaromatic blocks with hole and electron conducting properties. Efficient light emitting groups positioned at the polymer-polymer block junctions. are of interest in light emitting devices and are being investigated in collaboration with the Thompson group. Synthesis of Polymers with Applications in Direct Oxidation Methanol Fuel Cells. In collaboration with the Olah/Prakash groups we have shown that the use of (co)polymers in direct methanol oxidation fuel cells (DMFC’s) favorably mediates methanol utilization. For instance undesirable “methanol cross-over” may be reduced substantially using certain copolymers. The synthesis of new (co)polymers for DMFC’ membranes and other fuel cell applications is also a part of this program. Adhesive Properties of Novel Vinyl Copolymers. In collaboration with an industrial partner we have recently started a polymer synthesis program aimed at exploring fundamental copolymer structure-property relationships with respect to adhesion phenomena. This involves the synthesis and copolymerization of so called polymerizable vinyl monomers with large hydrocarbon pendent groups (“macromonomers”). The adhesive properties of these copolymers and its fundamental relationship with copolymer structure and topology is the main focus of this research.   References   1. Alberty,K. A. Hogen-Esch; T.E. Carlotti S. “Characterization and Fluorescence of Macrocyclic Polystyrene-2. Molecular Weight Dependent Properties”.Macromol. Chem and Phys 2005 ,206 (10) 1034 . 2. Shen, J-G; Hogen-Esch, T. E. “ Synthesis and characterization of poly 2-phenyl-5-(4-vinylphenyl)-1,3,4-oxadiazole using atom transfer radical polymerization.” Polymer Preprints (American Chemical Society, Division of Polymer Chemistry) 2005, 46(2), 1030. 3. Chen R.; Nossarev, G.,G.; Hogen-Esch T. E “Synthesis and Properties of Macrocyclic Vinylaromatic Polymers Containing a Single 1,4-Benzylidene or 9,10-Anthracenylidene Group”. Makromol. Chem. Macromol. Symp. 2004, 215, 67-79. 4. Chen R. Hogen-Esch T. E. “Synthesis and Spectroscopic Studies of Macrocyclic Poly (9,9-dimethyl-2-vinylfluorene)-b-Polystyrene Containing Single 9,10-Anthracenylidene Linking Units” . J. Pol. Sci. A. (Chem. Ed.) 2004, 42, 5488 5. S. Madhusoodhanan, M. E.; Hogen-Esch T. E.;Thompson, M.E. "Phosphorescence Quenching by Conjugated Polymers." J. Am. Chem. Soc. 2003,125(26),7796. 6. Da J.; Hogen-Esch T. E. “Synthesis and Association of Poly(N,N-dimethylacrylamide) Copolymers with Perfluorocarbon Pendent Groups Connected Through Polyethylene-glycol Tethers”. J. Pol. Sci. A. ( Chem. Ed.) 2004, 42, 360. 7. Madhusoodhanan S., Thompson M.E., Hogen-Esch T.E. “Reactive Oligomer Intermediates In The Yamamoto Coupling Mediated Polymerization of 2,7-Dibromofluorenes.” Polymer Preprints (American Chemical Society, Division of Polymer Chemistry) 2004, 45(2), 466. 8. Da J.; Hogen-Esch T. E. “Poly(N,N-dimethylacrylamide) with Perfluorocarbon Pendent Groups Connected Through Polyethylene-glycol Tethers Give Physical Gels in Organic Solvents”. Macromolecules 2003, 36, 9559-9563. 9. Chen R.; Zhang, X.; Hogen-Esch T. E. “Synthesis and Thermal Properties of Macrocyclic Poly(9,9-dimethyl-2-vinylfluorene) Containing Single 1,4-Benzylidene or 9,10-Anthracenylidene Linking Units” Macromolecules 2003, 36, 7477. 10. Chen R.; Johnson, J.; Bradforth, S.E. Hogen-Esch T. E “UV-Vis Absorption and Fluorescence Emission Spectroscopic Studies of Macrocyclic and Linear Poly(9,9-dimethyl-2-vinylfluorene). Evidence for Ground State Chromophore Interactions” Macromolecules 2003, 36, 9966. 11. Nossarev, G.G.; Hogen-Esch, T. E. "Synthesis and Thermal Properties of Macrocyclic Poly(2-vinylnaphthalene) Containing Single 1,4-Benzylidene or 9,10-Anthracenylidene Groups" Macromolecules, 2002, 35,1604. 12. Alberty, K. A. ; Tillman, E. ; Carlotti, S. ; King, K.; Bradforth, S. E.; Parker, D. ; Feast, W. J.; Hogen-Esch T. E "Characterization and Fluorescence of Macrocyclic Polystyrene by Anionic End to End Coupling. Role of Coupling Reagents" Macromolecules, 2002, 35, 3856 . 13. Gan, Y-D and Hogen Esch T..E. "Synthesis and Characterization of Catenated PS-Poly(2-vinylpyridine) Block Copolymers". Macromolecules 2002, 35, 7699. 14. Nossarev, G. G.; Hogen-Esch, T. E. "Living Anionic Polymerization of 2-Vinylnaphthalene in THF in the Presence of Lithium Ion. Role of Monomer Purification" Macromolecules, 2001,34,5373. 15. Alberty K.; Chen R.; Hogen-Esch T.E “A New Bifunctional Initiator for use in Anionic Polymerizations” J. Polym Sci. Part A: Polymer Chemistry, 2002, 40, 2108.