Kimble, Kyle William
(2008)
Advanced Hydrogels for Polymerized Crystalline Colloidal Array Materials.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
We developed a novel photo-polymerized hydrogel material and a new technique for embedding a crystalline colloidal array (CCA) within a thermo-reversible gelation polymer. The CCA lattice is locked into place within a polymeric hydrogel, forming a polymerized crystalline colloidal array (PCCA). The face-centered cubic (fcc) lattice into which the CCA self-assembles, Bragg diffracts light in the visible, near IR and UV regions of the spectrum. We utilized a poly(hydroxyethyl acrylate) hydrogel to detect ammonia in both buffer solutions and human serum. Phenols attached to the hydrogel backbone cross-link upon the addition of hypochlorite in a sample containing ammonia. The cross-linking causes an increase in the elastic constant of the hydrogel which forces the gel to shrink, blue-shifting the wavelength of Bragg diffracted light proportional to the concentration of ammonia present in solution. The sensor functions within the clinically relevant ammonia interval with a 50 μM detection limit in 1:1 serum/buffer solutions.A slight modification of this hydrogel material enabled its use within a bi-modular sensing approach for an organophosphorus (OP) nerve agent. The bi-modular sensing utilized the enzyme organophosphorus hydrolase (OPH) and the pH-sensitive group 3-aminophenol as recognition agents. OPH hydrolyzes OPs at basic pH and produces protons. These protons lower the pH inside the hydrogel changing the phenolates to phenols, lowering the free-energy of mixing and blue-shifting the Bragg diffracted light wavelength proportional to the OP concentration. The sensor is reversible, functions in high-ionic strength media, and has a 0.2 μM OP detection limit in aqueous media.We also developed a new technique for the synthesis of PCCA materials by embedding CCA within a thermo-reversible gelation polymer. Poly(vinyl alcohol) (PVA) in a solution of water and DMSO exhibits cononsolvency resulting in the formation of nanocrystallites, which act as physical cross-links. The hydrogel formed is thermo-reversible. It melts at 70oC and is optically clear when formed at temperatures below −10 oC. This gelation technique enables the facile synthesis of arbitrarily large PCCA materials.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
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| ETD Committee: |
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| Date: |
25 January 2008 |
| Date Type: |
Completion |
| Defense Date: |
5 October 2007 |
| Approval Date: |
25 January 2008 |
| Submission Date: |
3 October 2007 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Chemistry |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
color; DLVO; dynamic; Flory; interaction parameter; latex; light; microparticles; microspheres; nanoparticles; nanospheres; opal; PVA; PVOH; scattering; shrinking; swelling |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-10032007-213952/, etd-10032007-213952 |
| Date Deposited: |
10 Nov 2011 20:02 |
| Last Modified: |
15 Nov 2016 13:50 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/9429 |
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