Date of Award
Program or Major
Doctor of Philosophy
William Rudolf Seitz
A new imprinting occurs when polymerization is done in the presence of template. They involve three distinct types of crosslinks. Hydrophobic crosslinks are formed when poly (N-isopropylacrylamide) collapses to form a globule above its lower critical solution temperature (LCST). Acid-base crosslinks are formed by adding both acidic and basic monomers during polymerization. Minimal covalent crosslinker is included in the formulation so that the imprinted copolymer will return to the same conformation, even below the LCST. After free radical or reverse addition fragmentation chain transfer (RAFT) polymerization is complete, template is removed by dialysis.
The MIP binds with highest affinity at the LCST, where it collapses to a globule. The presence of the templated molecule was shown to reduce MIP aggregation above the LCST. This can be used as a physical signal to follow binding. Initial experiments used 4-nitrophenol as a template to establish optimum conditions to achieve rapid, selective, and high-affinity binding. Distribution ratios (([Template on Polymer])/([Template in Solution] )) as high as 4.57 ±0.0058 and selectivity to isomers of 4-nitrophenol as low as 1.33 ±0.0058 were measured by equilibrium dialysis.
Further experiments templated with fluorescein were conducted because it could be detected with higher sensitivity. Fluorescein binding constants were measured by equilibrium dialysis. A maximum value of 2.06x10^08 M was measured when working at low template concentrations. The value decreases as template concentration increases, indicating that not all sites bind with the same affinity. Kinetic experiments showed that binding is complete in less than two-seconds with 0.0355 mg/L of MIP and non-templated polymer shows no fluorescein binding.
This material is attractive as a chemical sensor because it can be tuned to any polar organic molecule. Capable of being a liquid, below the LCST, makes it possible to inkjet print on to paper based substrates. Attaching a fluorophore to the MIP enables a visual response to binding the template, α-tocopherol. Equilibrium dialysis revealed distribution ratios for α-tocopherol, 35.96 ±0.001, and its selectivity compound 4-hydroxycoumarin, 7.11 ±0.001.
Chemical separations can be achieved by removing compounds from solution using MIPs attached to gold nanoparticle (AuNP). The MIP’s RAFT end groups were reduced to a thiol which allows easy attachment to gold substrates. The binding constant of fluorescein was determined by the equilibrating fluorescein with MIP on AuNP and then removing them. A maximum value of 1.71x10^08 M was reported.
Grenier, Casey Joseph, "Rapid, High Affinity Binding by Molecularly Imprinted Poly(N-isopropylacrylamide) Copolymers with Mostly Non-Covalent Crosslinks for Chemical Sensing and Separation Applications" (2016). Doctoral Dissertations. 2267.
Available for download on Tuesday, December 01, 2116