Date of Award

1-1-2013

Document Type

Open Access Dissertation

Department

Chemistry and Biochemistry

Sub-Department

Chemistry

First Advisor

Ken D Shimizu

Abstract

Chemical sensors are important in a wide range of applications. However, there is no commercially available molecularly imprinted polymers (MIPs) based sensor. Thus, the design and development of sensors utilizing imprinting technique have been an area of active research. In Chapter 1, first a brief introduction to imprinting techniques is given. Then we provide a short review of progresses in design of MIPs sensors using multi-functional monomers. Multi-functional monomers (multi-FMs) are high affinity monomers towards target molecules and are able to introduce other functionally active groups for sensing and catalysis. Two classes of multi-FMs will be reviewed and discussed. Then, new advances which we have achieved and strategies which we have developed will be discussed at the end of this chapter.

A new method of verifying and characterizing the imprinting efficiency of molecularly imprinted polymers (MIPs) was developed and tested. In the new polar solvent titration (PST) method, a series of MIP and non-imprinted polymers (NIPs) are prepared with increasing concentrations of a polar solvent. The templation and monomer aggregation processes can be systematically disrupted by the polar solvent additives. The changes in the binding capacities of the polymers in each series provide a measure of the relative magnitudes of the imprinting effect and monomer aggregation effects. The new method was tested using three different urea functional monomers that had varying degrees of templation and monomer aggregation self-assembly. Diphenyl phosphate anion was used as template for these polymers. The new MIP characterization method can differentiate differences in binding capacity arising from templation and monomer aggregation. To independently verify the new characterization method, the MIPs were also characterized using the traditional binding isotherm analysis. The two methods appeared to give consistent conclusions. However, the results from the PST method provided more information about the presence and relative magnitudes of the templation and processes that influenced the binding properties of the polymers.

In Chapter 3, first we studied the importance of monomer aggregation for molecular imprinting. Monomer aggregation can improve the imprinting effect by suppressing the number of background binding sites. Then, the effects of crosslinking degree were evaluated using MAA and EA9A system. High crosslinking degree was required for imprinting effects. Higher crosslinked polymer exhibits greater imprinting effect. The relative magnitudes of the effect of crosslinking degree are estimated using urea functional monomers and phosphate template system. The effect of decreasing 13% of crosslinking degree was estimated to reduce 24% of the binding capacity. Next, the influence of functional monomer to template ratio on imprinting was studied and the range of this ratio was optimized. Finally, the above results were combined to design new functional monomers and new MIPs with improved imprinting effect.

A diacid functional monomer was shown to be a better monomer compared to MAA.

In Chapter 4, a lanthanide-containing polymer sensor was designed and prepared. This polymer showed sensitive and selective response to carboxylates. First a fluorescent europium-containing complex bearing styrene functionalities was synthesized. The complex was co-polymerized with EGDMA in dichloroethane under free radical polymerization conditions thermally. The sensing properties of the polymer were characterized by monitoring the fluorescence response using fluorimeter after pipetting a series of different anion solutions in varying concentrations. The polymer showed highly selectivity to carboxylate anions over halide and other oxy-anion analytes. Also, MIPs made with two different carboxylates showed better selectivity to the corresponding carboxylates.

Rights

© 2013, Di Song

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