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Heterogeneous
Catalysis
Current studies include detailed mechanistic and kinetic investigations of the
conversions of selected compounds over shape selective catalysts. The major effort at
present is concentrated on the reactions of low molecular weight halocarbons as catalyzed
by zeolites, specifically ZSM-5. The shape selectivity of the product formation observed
will be contrasted with that obtained from unhalogenated hydrocarbons. Isotopic labeling
and substituent effects are being investigated to provide mechanistic details of these
important reactions. Future studies will involve the extension of these investigations to
a broader range of heteroatoms containing organic compounds including phosphorus and
sulfur containing molecules.
Plasma Chemistry
In this work, we employ plasma deposition methods to obtain controlled surface
modifications for a variety of materials. The goal of this research is to provide
molecular level tailoring of surfaces for specific applications. Significant success in
this endeavor has been achieved through use of a variable duty cycle pulsed RF plasma
technique developed in our laboratory. In particular, we have been able to demonstrate
exceptional film chemistry control during plasma polymerization of a wide range of
monomers. Emphasis is placed on controlling both the nature and surface density of
specific functional groups introduced during the plasma treatment process. These surfaces
can subsequently be treated by more conventional chemical derivatization processes to
produce 3-dimensionally molecularly engineered structures.
There is a wide range of potential applications for the pulsed plasma treatment
processes we have developed. At present the major applications effort is devoted to
improving the biocompatability of implant materials. Future studies will include work in
catalysis and the development of improved membranes for separation processes.
Representative Publications:
"Subsurface Formation of Amide in
Polyethylene-co-Acrylic Acid Film: A Potentially Useful Reaction for Tethering
Biomolecules to a Solid Support," P. Zhang, N. Fawcett, Y. Wu and R. B. Timmons, Macromolecules,
32, 2149 (1999).
"Effects of Protein Surface Interactions on Protein Ion Signals in MALDI Mass
Spectrometry," A. K. Walker, Y. Wu, R. B. Timmons, K. D. Nelson and G. R. Kinsel, Anal.
Chem., 71, 268 (1999).
"Pulsed Plasma Polymerizations: Film Chemistry Control and Applications," Y. Wu,
L. M. Han, B. E. Thomes, H. Qiu, W. W. Lee and R. B. Timmons, Mater. Res. Soc.
Symposium Proceedings, 544, 77 (1999).
"Thin Film Plasma Deposition of Allylamine: Effects of Solvent Treatment," M. T.
Van Os, B. Menges, R. Förch, W. Knoll, R. B. Timmons and G. J. Vansco, Mater. Res.
Soc. Symposium Proceedings, 544, 45 (1999).
"Studies of Peptide Binding to Allylamine and Vinyl Acetic Acid Modified Polymers
Using MALDI-MS," A. K. Walker, H. Qiu, Y. Wu, R. B. Timmons and G. R. Kinsel, Anal.
Biochem., 271, 123 (1999).
"Influence of Sample Preparation Methodology on the Reduction of Peptide MALDI Ion
Signals by Surface-Peptide Binding," K. Chen, A. K. Walker, Y. Wu, R. B. Timmons and
G. R. Kinsel, J. Mass Spectrometry, 34, 1205 (1999)
"Progress in Bioresorable Polymer Stent Development," S. H. Su, J. Wu, C.
Landau, R. B. Timmons, R. S. Meidell, K. Nelson and R. C. Eberhart, Soc. Biomater.
Trans., XXII, 143 (1999).
"Surface Properties Affect the Extent of Fibrotic Responses to Implanted
Biomaterials," L. Tang, W. J. Hu, Y. Wu and R. B. Timmons, Soc. Biomater. Trans.,
XXII, 196 (1999).
"Pulsed Plasma Polymerization of 1-Vinyl-2-Pyrrolidone: Synthesis of a Linear
Polymer," L. M. Han and R. B. Timmons, J. Polym. Sci.: Part A: Polym. Chem.
36, 3121 (1998).
"Stability of Plasma-Polymerized Allylamine Films with Sterilization by
Autoclaving," J. G. Calderon, A. Harsch, G. W. Gross and R. B. Timmons, J. Biomed.
Mater. Res. 42, 597 (1998).
"Ring Retention During Pulsed Plasma Polymerization of Heterocyclic Aromatic
Compounds," L. M. Han, D. Bogdal and R. B. Timmons, Chem. Of Mater., 10,
1422 (1998).
"Pulsed Plasma Synthesis of Low Dielectric Constant Materials," L. M. Han, W. W.
Lee and R. B. Timmons, Mater. Res. Soc. Symposium Proc., 511, 93 (1998).
"Fibrinogen Adsorption and Host Tissue Responses to Plasma Functionalized
Surfaces," L. Tang, Y. Wu and R. B. Timmons, J. Biomed. Mater. Res., 42,
156 (1998).
"Pulsed Plasma Polymerization of Pentafluorostyrene: Synthesis of Low Dielectric
Constant Films," L. M. Han, R. B. Timmons, W. W. Lee, Y. Chen and Z. Hu, J. Appl.
Phys., 84 439 (1998).
"Surface Molecular Tailoring via Pulsed Plasma Deposited Acid Chloride Groups:
Synthesis and Reactivity," J. G. Calderon and R. B. Timmons, Macromolecules, 31,
3216 (1998).
"Pulsed Plasma Polymerization of Bromine Containing Monomers," J.-H. Wang, X.
Chen, J. Calderon, J.-J. Chen and R. B. Timmons, Plasmas and Polymers, 2,
241 (1997).
"Film Chemistry Control and Electrochemical Properties of Pulsed Plasma Polymerized
Ferrocene and Vinylferrocene," L. Han, K. Rajeshwar and R. B. Timmons, Langmuir, 13,
5941 (1997).
"Reduced Protein Adsorption on Plastics Via Direct Plasma Deposition of Triethylene
Glycol Monoallyl Ether," D. Beyer, W. Knoll, H. Ringsdorf, J.-H. Wang, P. Sluka and
R. B. Timmons, J. Biomed. Mater. Res, 36, 181 (1997).
"Pulsed Plasma Polymerization of Acryloyl Chloride: Functionalization of Surfaces
with Acid Chloride Groups," J. G. Calderon and R. B. Timmons, Polymer Preprints,
38, 1073 (1997).
"Plasma Synthesis of a Novel CF3-Dominated Fluorocarbon Film," J.-H. Wang, J.-J.
Chen and R. B. Timmons, Chem. Mater., 8, 2212 (1996).
"Pulsed Radio Frequency Plasma Polymerization of Allyl Alcohol: Control Deposition of
Surface Hydroxyl Groups," C. L. Rinsch, X. Chen, J.-H. Wang, R. C. Eberhart and R. B.
Timmons, Langmuir, 12, 2995 (1996).
"Pulsed Plasma Polymerization of Tetramethyltin: Nanoscale Compositional Control of
Film Chemistry," X. Chen, K. Rajeshwar, J.-J. Chen, O. M. R. Chyan and R. B. Timmons,
Chem. Mater., 8, 1067 (1996).
"Film Chemistry Control During Pulsed Plasma Polymerization of Allyl Alcohol and
Allyl Amine," C. L. Rinsch, X. Chen, V. Panchalingam, C. R. Savage, J.-H. Wang, R. C.
Eberhart and R. B. Timmons, Polym. Preprints, 36, 95 (1995).
"Use of a Variable Duty Cycle Pulsed RF Plasma to Improve Adhesion of Plasma
Polymerized Films on Various Substrates," Pacific Polymer Federation Preprints,
4th Pacific Polymer Conference, p. 11 (1995).
"Improved Biocompatibility of Materials via Pulsed RF Plasma Polymerizations,"
V. Panchalingam, R. C. Eberhart, C. R. Savage and R. B. Timmons, in Polymer
Biomaterials in Solution, as Interfaces, and as Solids, S. L. Cooper, C.
H. Bamford and T. Tsuruta (Eds.), VSP Publishers (Netherlands), pp. 3-17 (1995).
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