Date of Award
Program or Major
Doctor of Philosophy
W Rudolf Sweitz
Lightly cross-linked, animated polymers that swell and shrink with changing pH were prepared and evaluated. At low pHs amine sites protonate causing charge to accumulate along the polymer backbone. The polymer then swells to maximize the charge separation. The swelling of the polymer causes a change in a magnetic or optical property that can be measured and related to pH.
Animated hydrogel membranes were prepared by copolymerizing dimethyl amino ethyl methacrylate(DMAEMA) with various comonomer hydrogels. Experiments were conducted to examine the effect of formulation on the ability of the hydrogel membrane to swell. Factors examined included cross-linker type, cross-linker concentration, DMAEMA concentration and comonomer hydrophilicity.
Polymer microspheres were prepared using dispersion polymerization and seeded emulsion polymerization techniques. Poly-(vinyl benzyl chloride-co-2,4,5-trichloro phenyl acrylate)(VBC/TCPA) microspheres were prepared by dispersion polymerization. A factorial design experiment was carried out to examine the effect of monomer concentration, stabilizer concentration and water concentration on the size of VBC/TCPA particles stabilized with poly-acrylic acid. Microspheres were prepared using poly(vinylpyrrolidone) as the steric stabilizer. These particles were 0.6 mum in diameter and were used in optical sensing experiments. Seeded emulsion polymerization was used to produce porous particles of poly(VBC) with diameters of 1.3 mum.
The pH sensitive hydrogel membranes were incorporated into two types of magnetochemical sensors; the magnetostatic coupled sensor and the magnetoelastic sensor. Both sensor designs responded to solution pH due to swelling or shrinking of the hydrogel. In addition, the magnetoelastic strip was evaluated for measuring viscosity and for monitoring polymerization processes.
VBC/TCPA microspheres were used in several optical sensing methods. Poly(vinyl alcohol) membranes with VBC/TCPA microspheres were used to examine the feasibility of monitoring solution pH by surface plasmon resonance. A number of hydrogels of varying hydrophilicities with VBC/TCPA microspheres were examined by UV/Vis spectrophotometry, to examine the effect of membrane hydrophilicity on response for potential use in a remote fiber optic chemical sensor. The reproducibility of poly(VBC) microspheres in a HEMA membrane was examined. No change in response was observed after 100 swelling and shrinking cycles. Exposure to 80°C temperature or light for 40 days had only a small change on the magnitude of response.
Doherty, Stephen Arnold, "Swellable polymer substrates for use in magnetochemical and optical chemical sensing" (2000). Doctoral Dissertations. 2119.