Linked Life Data

18271586

Source:http://linkedlifedata.com/resource/pubmed/id/18271586

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
10
pubmed:dateCreated
2008-3-6
pubmed:abstractText
The surface of monodisperse silica particles synthesized using the Stober process were coated with a thin layer of polystyrene. Surface charge groups were attached by a grafting polymerization of styrene sulfonate. The resulting highly charged monodisperse silica particles self-assemble into crystalline colloidal arrays (CCA) in deionized water. We polymerized hydroxyethyl methacrylate (HEMA) around the CCA to form a HEMA-polymerized crystalline colloidal array (PCCA). Hydrofluoric acid was utilized to etch out the silica particles to produce a three-dimensional periodic array of voids in the HEMA PCCA. The diffraction from the embedded CCA sensitively monitors the concentration of ethanol in water because the HEMA PCCA shows a large volume dependence on ethanol due to a decreased Flory-Huggins mixing parameter. Between pure water and 40% ethanol the diffraction shifts across the entire visible spectral region. We accurately modeled the dependence of the diffraction wavelength on ethanol concentration using Flory theory. We also fabricated a PCCA (which responds to pH changes in both low and high ionic strength solutions) by utilizing a second polymerization to incorporate carboxyl groups into the HEMA PCCA. We were also able to model the pH dependence of diffraction of the HEMA PCCA by using Flory theory. An unusual feature of the pH response is a hysteresis in response to titration to higher and lower pH. This hysteresis results from the formation of a Donnan potential at high pH which shifts the ionic equilibrium. The kinetics of equilibration is very slow due to the ultralow diffusion constant of protons in the carboxylated PCCA as predicted earlier by the Tanaka group.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Mar
pubmed:issn
1520-5126
pubmed:author
pubmed:issnType
Electronic
pubmed:day
12
pubmed:volume
130
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
3113-9
pubmed:meshHeading
pubmed:year
2008
pubmed:articleTitle
Polymerized PolyHEMA photonic crystals: pH and ethanol sensor materials.
pubmed:affiliation
Department of Chemistry, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA.
pubmed:publicationType
Journal Article, Research Support, N.I.H., Extramural