Scott M. Husson, Ph.D. -- Research Activities

Thrust 2: Synthesis and Characterization of Polymers with “Memory”
The primary objective in this thrust area is to synthesize and characterize “designer” thermoset polymers that perform molecular recognition. To achieve this objective, we use a templating technique to produce molecularly imprinted polymers (MIPs). Here I discuss our work on surface molecular imprinting.

Surface Molecular Imprinting by Atom Transfer Radical Polymerization
Overview: Molecular imprinting is a templating technique that is used to produce physically and chemically selective binding sites in a polymer matrix. In this method, a cross-linked polymer is formed around a template molecule. A high percentage of crosslinker is used to form rigid and insoluble polymers. After the template is extracted, imprint cavities remain in the polymer with functional groups that are capable of specific interaction with the template. These sites complement the template molecule in size, shape, and position of interacting functionalities. Consequently, they recognize the template and exhibit template-selective binding.

Opportunity: Many applications that use molecularly imprinted polymers (MIPs) will employ them as surface coatings on solid support materials. A 2-D platform (i.e., an ultrathin polymer coating) has the potential to overcome mass transfer limitations and non-quantitative recovery of the template molecule seen for imprinted materials fabricated by conventional 3-D methods, such as bulk polymerization, that lead to MIP particles or thick films. In order to develop applications of MIPs for commercial use, a methodology is needed to synthesize uniform 2-D surface films with controllable and ultrathin layer thicknesses.

Research activities and findings: Figure 3 illustrates our strategy for preparing the 2-D MIP materials. The foundation is a solid support material (e.g., polymeric film or membrane, silica, gold, etc.) that is capped with polymerization initiator molecules (?). The initiator molecules are anchored covalently to the support; subsequently, the polymer chains grow from these initiator sites and remain confined to the surface. Finally, in the presence of a template molecule and cross-linking agent(s), imprints can be formed at the polymer film periphery.

In a recent study, we used this strategy to prepare a poly(2-vinylpyridine-co-ethylene glycol dimethacrylate) film imprinted against N,N’-didansyl-L-cystine. A non-imprinted polymer (NIP) film was prepared as control. Characterization of the physical and chemical properties of the surfaces was done by ellipsometry, external reflectance-FTIR, SPM, and x-ray photoelectron spectroscopy (XPS) measurements. Polymer growth rate was monitored by ellipsometry. SPM showed that there were no apparent morphological differences between the two surfaces that might contribute to differences in template binding. XPS was used to measure the atomic composition of the copolymer films. Under the conditions used, the MIP and non-imprinted surfaces had the same surface composition.

Figure 4 presents rebinding isotherms for N,N’-didansyl-L-cystine on MIP and NIP surfaces. Fluorometry was used to quantify the binding capacities. Over the entire range of solution template concentrations, the imprinted film showed higher binding capacities than the non-imprinted film.

Figure 3. Schematic illustration of the process to form ultrathin MIPs on a solid substrate.

Figure 4. Binding isotherms for N,N’-didansyl-L-cystine on imprinted and non-imprinted surfaces.

In this thrust area, we have also used surface plasmon resonance spectroscopy to measure adsorption isotherms on MIP and NIP surfaces in aqueous solution where pH effects are important. In addition, we have begun to explore imprinting of electroconductive polymer films for environmental sensing applications.

Last Updated:April 18, 2009 -- Site Maintained by: Donna Kilbourne
Department of Chemical and Biomolecular Engineering
Clemson University, 127 Earle Hall, Clemson, SC 29634-0909
Phone: (864) 656-3055 -- FAX: (864) 656-0784

Clemson Home -- College Home -- Department Home
calendars -- campus map -- campus tour -- phonebook -- search -- webmail

Copyright © 2002-2006, Clemson University. All rights reserved.
Clemson University, Clemson, South Carolina 29634 -- Area Code: 864, Information: 656-3311