HYBRID PARTICLES AND MEMBRANES BASED ON POLYSILSESQUIOXANE BUILDING BLOCKS WITH FLUORESCENT DYES

Persistent Link:
http://hdl.handle.net/10150/205421
Title:
HYBRID PARTICLES AND MEMBRANES BASED ON POLYSILSESQUIOXANE BUILDING BLOCKS WITH FLUORESCENT DYES
Author:
Li, Zhe
Issue Date:
2011
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Embargo:
Embargo: Release after 06/05/2012
Abstract:
Sol-gel processing has been demonstrated to produce supported inorganic and hybrid microporous membranes with controlled physical and chemical properties under mild conditions. In preparing asymmetric membranes on mesoporous ceramic supports using traditional sol-gel processes, however, infiltration of the final coating material from smaller nanoparticles into the porous support can lead to unpredictable membrane thicknesses, poor reproducibility and reduced flux for separations.Herein we describe a size exclusion approach to prepare membranes by depositing well-defined relatively monodisperse particles on a mesoporous ceramic support. Ensuring that the particles remain on the surface by size exclusion can reduce or even eliminate infiltration. But if the porosity of the membrane top-layer is going to be finer than that of the support, it must be possible to sinter the particles to eliminate the interstitial porosity. Low temperature sintering is accomplished by preparing relatively compliant polysilsesquioxane particles through the introduction of organic substituents into the network of particles.To prepare membranes by size exclusion, we developed a sol-gel route to synthesize bridged polysilsesquioxane particles by polymerizing a dilute solution of monomers below their gelation concentration. Dynamic light scattering was used to monitor the particle size and size distributions during polymerizations up to the formation of gels. A membrane top-layer was successfully coated on a mesoporous titania-zirconia support through size exclusion of octylene- bridged polysilsesquioxane particles. To assist in determining if infiltration into the support has occurred and if particles are size-excluded from penetrating the support, we have covalently modified polysilsesquioxane particles with a fluorescent dye to provide direct visual evidence of the location of particles in the ceramic membrane. This is the first report of fluorescent diagnostics being used to detect infiltration and verify size exclusion of particles in asymmetric membrane deposition. We further created supported membranes of poly(phenylsilsesquioxane) through size exclusion of particles deposited on the support and then cured to establish a glassy, defect-free membrane coating without infiltration upon thermal exposure. Infiltration was verified with fluorescent dyes covalently bound into the particles. The size exclusion approach combined with fluorescent diagnostics allowed for the simplification of membrane formation and elimination of infiltration.
Type:
text; Electronic Dissertation
Keywords:
Infiltration; Membranes; Polysilsesquioxanes; Sol-gel; Materials Science & Engineering; Fluorescent probes; Hybrid particles
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Materials Science & Engineering
Degree Grantor:
University of Arizona
Advisor:
Loy, Douglas A.

Full metadata record

DC FieldValue Language
dc.language.isoenen_US
dc.titleHYBRID PARTICLES AND MEMBRANES BASED ON POLYSILSESQUIOXANE BUILDING BLOCKS WITH FLUORESCENT DYESen_US
dc.creatorLi, Zheen_US
dc.contributor.authorLi, Zheen_US
dc.date.issued2011-
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.releaseEmbargo: Release after 06/05/2012en_US
dc.description.abstractSol-gel processing has been demonstrated to produce supported inorganic and hybrid microporous membranes with controlled physical and chemical properties under mild conditions. In preparing asymmetric membranes on mesoporous ceramic supports using traditional sol-gel processes, however, infiltration of the final coating material from smaller nanoparticles into the porous support can lead to unpredictable membrane thicknesses, poor reproducibility and reduced flux for separations.Herein we describe a size exclusion approach to prepare membranes by depositing well-defined relatively monodisperse particles on a mesoporous ceramic support. Ensuring that the particles remain on the surface by size exclusion can reduce or even eliminate infiltration. But if the porosity of the membrane top-layer is going to be finer than that of the support, it must be possible to sinter the particles to eliminate the interstitial porosity. Low temperature sintering is accomplished by preparing relatively compliant polysilsesquioxane particles through the introduction of organic substituents into the network of particles.To prepare membranes by size exclusion, we developed a sol-gel route to synthesize bridged polysilsesquioxane particles by polymerizing a dilute solution of monomers below their gelation concentration. Dynamic light scattering was used to monitor the particle size and size distributions during polymerizations up to the formation of gels. A membrane top-layer was successfully coated on a mesoporous titania-zirconia support through size exclusion of octylene- bridged polysilsesquioxane particles. To assist in determining if infiltration into the support has occurred and if particles are size-excluded from penetrating the support, we have covalently modified polysilsesquioxane particles with a fluorescent dye to provide direct visual evidence of the location of particles in the ceramic membrane. This is the first report of fluorescent diagnostics being used to detect infiltration and verify size exclusion of particles in asymmetric membrane deposition. We further created supported membranes of poly(phenylsilsesquioxane) through size exclusion of particles deposited on the support and then cured to establish a glassy, defect-free membrane coating without infiltration upon thermal exposure. Infiltration was verified with fluorescent dyes covalently bound into the particles. The size exclusion approach combined with fluorescent diagnostics allowed for the simplification of membrane formation and elimination of infiltration.en_US
dc.typetexten_US
dc.typeElectronic Dissertationen_US
dc.subjectInfiltrationen_US
dc.subjectMembranesen_US
dc.subjectPolysilsesquioxanesen_US
dc.subjectSol-gelen_US
dc.subjectMaterials Science & Engineeringen_US
dc.subjectFluorescent probesen_US
dc.subjectHybrid particlesen_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineMaterials Science & Engineeringen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorLoy, Douglas A.en_US
dc.contributor.committeememberUhlmann, Donald R.en_US
dc.contributor.committeememberCorrales, Rene L.en_US
dc.contributor.committeememberCorral, Erica L.en_US
dc.contributor.committeememberLoy, Douglas A.en_US
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