Organic and Polymer Chemistry
The research in my group seeks to use the knowledge and techniques of organic chemistry to prepare and characterize materials. These materials are synthetic polymers or polymer additives. The materials are chosen for their unusual structures, or for certain useful or unusual properties, such as photosensitivity, molecular recognition, and catalysis.
Microlithography is the process used for printing integrated circuits. One requirement is a light sensitive material which changes its reactivity or solubility on irradiation: this material is known as a photoresist. The sensitivity of a photoresist is the amount of light required to generate an image. The resolution is the smallest feature which can be produced in the resist. An improved photoresist will resolve smaller features using less light. Light of shorter wavelengths allows smaller features to be resolved, but usually at a cost in sensitivity. Sensitivity can be increased by linking a catalytic process to the photochemistry - a method known as chemical amplification. We are currently studying a number of catalysts and materials for chemically amplified photoresists: arylmethyl sulfones as photoacid generators, quaternary ammonium salts as photobase generators, and a variety of oligomeric structures as dissolution inhibitors.
Dendritic polymers or dendrimers are highly branched polymers with a regular branching motif. These materials were first made in the 1980s, and have many unusual properties. They can be synthesized by divergent or convergent techniques. Our research involves dendrimers made by the convergent technique, which provides extremely monodisperse materials. We have made significant advances in synthetic methodology, and are currently working with photoactive labels to characterize the properties of these materials in solution.
Molecular imprinting is a technique for creating polymers which
recognize other molecules. In the traditional method, a highly
cross-linked polymer is synthesized in the presence of a template
molecule. The resulting polymer is ground into a powder and thoroughly
extracted. The resulting material will display a high affinity
for the template moleculebecause there are cavities in the polymer
which match the template in size, shape, and polarity. Our research
in molecular imprinting seeks to devise materials that are easier
to make and can be erased and re-imprinted. This requires reversible
cross-linking interactions, whether hydrogen bonds or covalent
"Weak Temperature Dependence of Electron Transfer Rates in Fixed-Distance Porphyrin -Quinone Model Systems" L.R.Khundkar, J.W.Perry, J.E.Hanson, P.B.Dervan. Journal of the American Chemical Society 1994, 116, 9700-9709.
"The 1.4 and 248 nm Radiation Response of Chemically Amplified Resists Containing Arylmethyl Sulfone Photoacid Generators" Hanson, J.E.; Pingor, D.A.; Novembre, A.E.; Kometani, J.M.; Tai, W.W. Polymers for Advanced Technology, 1994, 5, 49-55.
"Photoacid and Photobase Generators: Arylmethyl Sulfones and Ammonium Salts" Hanson, J.E.; Jensen, K.H.; Gargiulo, N.; Motta, D.; Pingor, D.A.; Novembre, A.E.; Mixon, D.A.; Kometani, J.M.; Knurek, C. Polymeric Materials: Science and Engineering, 1995, 72, 201-202.
"New Approaches to the Synthesis of Poly(aryl ether) Dendrimers" Tyler, T.L.; Hanson, J.E. Polymeric Materials: Science and Engineering, 1995, 73, 356-357.
"Chromophore Labelled Dendrimers: Photophysical Probes of Dendrimer Structure and Dynamics" Hanson, J.E.; Murphy, W.R.; Riley, J.M.; Tyler, T.L.; Kelley, S.O.; Makarewicz, A.M. Polymeric Materials: Science and Engineering, 1995, 73, 358-359.
"Photoacid and Photobase Generators:
Arylmethyl Sulfones and Benzhydrylammonium Salts" J.E.Hanson,
K.H.Jensen, N.Gargiulo, D.Motta, D.A.Pingor, A.E.Novembre, D.A.Mixon,
J.M.Kometani, C.Knurek; a chapter in Microelectronics Technology:
Polymers for Advanced Imaging and Packaging, American Chemical
Society, Washington DC: 1995.