Douglas Loy
University of Arizona, Materials Science and Engineering, Faculty Member
Hydrolysis and condensation of trialkoxysilanes, R-Si(ORâ²)â, generally leads to the formation of silsesquioxane oligomers and polymers. These polymers are composed of a monomer repeat unit, [R-SiO{sub 1.5}]{sub n}, with a single silicon... more
Hydrolysis and condensation of trialkoxysilanes, R-Si(ORâ²)â, generally leads to the formation of silsesquioxane oligomers and polymers. These polymers are composed of a monomer repeat unit, [R-SiO{sub 1.5}]{sub n}, with a single silicon atom attached to other repeat units in the polymer through one to three siloxane bonds. The remaining substituent is an organic group attached to the silicon through a silicon-carbon single bond. Silsesquioxanes have been the subject of intensive study in the past and are becoming important again as a vehicle for introducing organic functionalities into hybrid organic-inorganic materials through sol-gel processing. Despite all of this interest, there has not been a systematic study of the ability of trialkoxysilanes to form gels through the sol-gel process. In fact, it has been noted that silsesquioxanes are generally isolated as soluble resins rather than the highly crosslinked network polymers (gels) one would expect from a tri-functional monomer....
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Organopolysilsesquioxanes have recently gained much interest as materials for low-K dielectrics [1], ceramic precursors [2] and photoresists [3]. Typical sol-gel synthesis of polysilsesquioxanes involves the hydrolysis of... more
Organopolysilsesquioxanes have recently gained much interest as materials for low-K dielectrics [1], ceramic precursors [2] and photoresists [3]. Typical sol-gel synthesis of polysilsesquioxanes involves the hydrolysis of organotricholorosilanes and/or organotrialkoxysilanes in the presence of acid or base catalysts and organic solvents. However, under sol-gel conditions most organotrialkoxysilanes do not afford silsesquioxane gels. This limits the range of organic functionalities that can be introduced into these hybrid organicinorganic materials.
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Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid orgainc-inorganic materials [1]. These materials have shown promise as precursors for encapsulation and... more
Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approach to sol-gel type hybrid orgainc-inorganic materials [1]. These materials have shown promise as precursors for encapsulation and microelectronics applications (Figure 1). The polymers are highly crosslinked and are structurally similar to traditional sol-gels, but unlike typical sol-gels they are prepared by an organic base or Bronsted acid (formic or triflic acid), without the use of solvents and water, they have low VOC's and show little shrinkage during processing.
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Research Interests: Chemical Engineering, Materials Science, Chemistry, Membranes, Polymerization, and 15 moreMolecular modeling, Polymer, Porosity, Computer Simulation, Sol Gel Process, Silica, Molecular Sieve, Fabrication, Membrane, Template, Monomer, Molecular Sieves, Low Temperature, Monomers, and Mesoporous Material
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Research Interests: Chemical Engineering, Condensed Matter Physics, Materials Science, Chemistry, Surfaces and Interfaces, and 12 moreElectrochemistry, Spectroscopy, Medicine, Multidisciplinary, Nanoporous, Cationic polymerization, Hybrid Architecture, Anionic Surfactant, Langmuir, Ring Closing Metathesis, Pulmonary Surfactant, and Depolymerization
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ABSTRACTSol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. We have developed a new class of hybrid organic-inorganic materials... more
ABSTRACTSol-gel processing of materials is plagued by shrinkage during polymerization of the alkoxide monomers and processing (aging and drying) of the resulting gels. We have developed a new class of hybrid organic-inorganic materials based on the solventless ring-opening polymerization (ROP) of monomers bearing the 2,2,5,5-tetramethyl-2,5-disilaoxacyclopentyl group, which permits us to drastically reduce shrinkage in sol-gel processed materials. Because the monomers are polymerized through a chain growth mechanism catalyzed by base rather than the step growth mechanism normally used in sol-gel systems, hydrolysis and condensation products are entirely eliminated. Furthermore, since water is not required for hydrolysis, an alcohol solvent is not necessary. Monomers with two disilaoxacyclopentyl groups, separated by a rigid phenylene group or a more flexible alkylene group, were prepared through disilylation of the corresponding diacetylenes, followed by ring closure and hydrogenati...
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ABSTRACTPolymerization of organotrialkoxysilanes is a convenient method for introducing organic functionality into hybrid organic-inorganic materials. However, not much is known about the effects of the organic substituent on the porosity... more
ABSTRACTPolymerization of organotrialkoxysilanes is a convenient method for introducing organic functionality into hybrid organic-inorganic materials. However, not much is known about the effects of the organic substituent on the porosity of the resulting xerogels. In this study, we prepared a series of polysilsesquioxane xerogels from organotrialkoxysilanes, RSi(OR′)3, with different organic groups (R = H, Me, Et, dodecyl, hexadecyl, octadecyl, vinyl, chloromethyl, cyanoethyl). Polymerizations of the monomers were carried out under a variety of conditions, varying monomer concentration, type of catalyst, and alkoxide substituent. The effect of the organic substituent on the sol-gel process was often dramatic. In many cases, gels were formed only at very high monomer concentration and/or with only one type of catalyst. All of the gels were processed as xerogels and characterized by scanning electron microscopy and nitrogen sorption porosimetry to evaluate their pore structure.
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ABSTRACTIn-situ filling through hydrolysis and condensation of silicon alkoxides dissolved into polymers has been utilized to generate nanocomposites in which the filler phase can be intimately associated with the polymer on relatively... more
ABSTRACTIn-situ filling through hydrolysis and condensation of silicon alkoxides dissolved into polymers has been utilized to generate nanocomposites in which the filler phase can be intimately associated with the polymer on relatively small length scales. One problem of the method has been achieving useful fill volumes without bulk phase separation of the growing inorganic component from the polymer. In this paper, we describe the preparation of a new class of nanocomposite materials in which the inorganic filler phase is pre-assembled before copolymerization with an organic monomer. Maleimide monomers, prepared from alkoxysilylpropyl amines and maleic anhydride, were protected against side reactions by forming the oxonorbornene Diels-Alder adduct with furan. The monomers were then reacted under solgel conditions to form oligomers or polymers making up the filler phase. The material was activated by thermal deprotection of the maleimide and reacted with organic monomers or polymers...
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This issue of MRS Bulletin focuses on the preparation and application of hybrid organic–inorganic materials, which are broadly defined as synthetic materials with organic and inorganic components. Hybrid organic–inorganic materials are of... more
This issue of MRS Bulletin focuses on the preparation and application of hybrid organic–inorganic materials, which are broadly defined as synthetic materials with organic and inorganic components. Hybrid organic–inorganic materials are of two kinds: homogeneous systems derived from monomers or miscible organic and inorganic components, and heterogeneous and phase-separated systems with domains ranging from angstroms to micrometers in size.
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Research Interests: Engineering, Materials Science, Chemistry, Materials Chemistry, Polymer Chemistry, and 14 moreMass Spectrometry, Polymerization, Sol Gel Process, CHEMICAL SCIENCES, Surface Area, Monomer, Chemical Bonds, Reaction Mechanism, Hydrolysis, Experimental Data, Copolymer, Molecular Structure, Nuclear Magnetic Resonance Spectroscopy, and Dispersity
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The study of a homologous series of precursors to bridged polysilsesquioxanes has uncovered striking discontinuities in gelation behavior. An investigation of the chemistry during the early stages of the polymerization has provided a... more
The study of a homologous series of precursors to bridged polysilsesquioxanes has uncovered striking discontinuities in gelation behavior. An investigation of the chemistry during the early stages of the polymerization has provided a molecular basis for these observations. Monomers containing from one to four bridging carbon atoms exhibit a pronounced tendency to undergo rapid intra- or bimolecular cyclization. The cyclic and bicyclic intermediates have been characterized by (29)Si NMR spectroscopy, chemical ionization mass spectrometry, and isolation from the reaction solution. These carbosiloxanes are local thermodynamic sinks that produce kinetic bottlenecks in the production of high-molecular-weight silsesquioxanes. The formation of cyclic carbosiloxanes results in slowing, or in some cases completely shutting down, gelation. An additional finding is that the cyclic structures are incorporated intact into the final xerogel.
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... Douglas A. Loy, and Darryl Y. Sasaki* . ... Biophysical and Functional Characterization of an Ion Channel Peptide Confined in a Sol−Gel Matrix. Roc o Esquembre, Jos Antonio Poveda and C. Reyes Mateo. The Journal of Physical... more
... Douglas A. Loy, and Darryl Y. Sasaki* . ... Biophysical and Functional Characterization of an Ion Channel Peptide Confined in a Sol−Gel Matrix. Roc o Esquembre, Jos Antonio Poveda and C. Reyes Mateo. The Journal of Physical Chemistry B 2009 113 (21), 7534-7540. ...
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... Owen W. Webster Central Research & Developmentt EI du Pont de Nemours & Company Experimental Station, Wilmington, Delaware 19898 Received July 24, 1989 ... In a typical pro-cedure,... more
... Owen W. Webster Central Research & Developmentt EI du Pont de Nemours & Company Experimental Station, Wilmington, Delaware 19898 Received July 24, 1989 ... In a typical pro-cedure, monomer 3a (0.2-0.4 M in THF or EtOH) was hydrolyzed/condensed with 3 equiv of H 2 ...
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... Roger A. Assink,a^ James E. Schirber, Douglas A. Loy, Bruno Morosin, and Gary A. Carlson Sandia National Laboratories, Albuquerque, New Mexico 87185 ... we expect that it can also contribute to the relaxation of C6o molecules not in... more
... Roger A. Assink,a^ James E. Schirber, Douglas A. Loy, Bruno Morosin, and Gary A. Carlson Sandia National Laboratories, Albuquerque, New Mexico 87185 ... we expect that it can also contribute to the relaxation of C6o molecules not in direct contact with the oxygen mole-cule. ...
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... 29 Si CP MAS NMR spectrum of the phenylene-bridged polysilsesquioxane aerogel polymerized in ... We believe that this technique will greatly simplify the preparation of aerogels and open a ... frontier for sol−gel processing using... more
... 29 Si CP MAS NMR spectrum of the phenylene-bridged polysilsesquioxane aerogel polymerized in ... We believe that this technique will greatly simplify the preparation of aerogels and open a ... frontier for sol−gel processing using SCCD or other nonpolar organic solvents coupled ...
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We first focused on the sol−gel polymerization of methyltrimethoxysilane, one of the few organotrialkoxysilanes that forms gels with base or acid catalysts in a reasonably short time. 10 However, it was not possible to prepare... more
We first focused on the sol−gel polymerization of methyltrimethoxysilane, one of the few organotrialkoxysilanes that forms gels with base or acid catalysts in a reasonably short time. 10 However, it was not possible to prepare polymethylsilsesquioxane gels except at high or low pH regardless of ...
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... Todd M. Alam,* Roger A. Assink, and Douglas A. Loy. Properties of Organic Materials Department, Sandia National Laboratories, Albuquerque, New Mexico 87185-1407. Chem. Mater. , 1996, 8 (9), pp 23662374. DOI: 10.1021 ...
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In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing mobilization of the polymeric network. The bridging organic group contains latent functionalities that can... more
In this paper, we introduce a new approach for altering the properties of bridged polysilsesquioxane xerogels using post-processing mobilization of the polymeric network. The bridging organic group contains latent functionalities that can be liberated thermally, photochemically, or by ...
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We report the first synthesis of spherical nanoparticles of a bridged polysilsesquioxane. The hard, brittle nanoparticles are prepared by a simple sol-gel polymerization without surfactants or templates. Particle size ranges from 50 to... more
We report the first synthesis of spherical nanoparticles of a bridged polysilsesquioxane. The hard, brittle nanoparticles are prepared by a simple sol-gel polymerization without surfactants or templates. Particle size ranges from 50 to 100 nm. The organic component of these hybrid nanoparticles is composed of a photolabile coumarin dimer. Irradiation with UV light dissociates the photodimer resulting in rupture of the cross-links and subsequent deformation and eventual "melting" of the nanoparticles.