Date of Award
Program or Major
Doctor of Philosophy
W Rudolf Seitz
Swellable thermoresponsive and lightly cross-linked polymer microparticles were prepared for the development of chemical sensors for various target analytes. The swelling and shrinking of the polymer particles as a function of concentration of target analytes has been investigated using turbidity and fluorescence measurements at suitable pH values.
Chemical sensors that respond to transition metal ions such as Cu 2+, Ni2+, Zn2+, and Pb2+ were prepared by copolymerizing N-Isopropylacrylamide (NIPAAm) with ligands such as; 2,2'-acylamidodiacetic acid (AIDA), dibutyl-2,2'-(3 vinylphenylazanediyl) diacetate (DVPAA), N-((4'-methyl-2,2'-bipyridin-4yl)methyl)-N-propylacrylamide (NMPPAAm), and N,N-bis(pyridine-2-ylmethyl)prop-2-en-1-amine (NBPMPA). The microparticles were either labeled with 9-vinylanthracene (9-VA)/2-Naphthylmethacrylate (2-NMA), or fluorescein o-acrylate/methacryloxethyl thiocarbonyl rhodamine B fluorophore pairs. The particles were cross-linked using between 5--8% N, N-methylenebisacrylamide (MBA) and stabilized in acetonitrile using poly (styrene-co-acrylonitrile). The microparticles were suspended in pH 6 MOP buffer with ionic strength adjusted to 0.1M. The shrinking and swelling properties of the polymer microparticles with change in analyte concentration were evaluated by fluorescence measurements. Fluorescence intensity ratios of the acceptor to the donor fluorophores in the microparticles were calculated at different analyte concentrations.
Another method was developed for preparing sensors that respond to both beta-D-glucopyranose and theophylline molecules by imprinting them in to a lightly cross-linked polymer network prepared by dispersion polymerization in water and acetonitrile, respectively. The molecular imprinting of beta-D-glucopyranose and theophylline was achieved by using acrylamide and methacrylic acid (MAA), respectively, as functional monomers.
The theophylline imprinted polymer particles were labeled with fluorescein o-acrylate and methacryloxethyl thiocarbonyl rhodamine B fluorophores. MBA and poly (styrene-co-acrylonitrile) were used as cross-linker and stabilizer respectively in the polymer synthesis. Fluorescence measurements were used to monitor the swelling and shrinking of the polymer particles. The particles responded to theophylline concentration as low as 10-7M in pH 7 buffer. In the preparation of beta-D-glucopyranose imprinted polymer particles, poly (vinyl pyrrolidone) (PVP) was used as the stabilizer. The particles were immobilized in 10% poly (vinyl alcohol) (PVA) membranes and suspended in MOP buffer pH 7 for turbidity measurement. It was shown that these particles respond to beta-D-glucopyranose concentration as low as 10-5M.
Osambo, John Ong'any, "Chemical sensors based on swellable polymer microparticles and molecular imprinted polymers" (2009). Doctoral Dissertations. 514.