Douglas Loy | University of Arizona (original) (raw)
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Hydrolysis and condensation of trialkoxysilanes, R-Si(ORâ²)â, generally leads to the formation of... 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....
MRS Proceedings, 2000
Organopolysilsesquioxanes have recently gained much interest as materials for low-K dielectrics [... 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.
MRS Proceedings, 2000
Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approac... 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.
MRS Proceedings, 1999
ABSTRACTSol-gel processing of materials is plagued by shrinkage during polymerization of the alko... 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...
Hydrolysis and condensation of trialkoxysilanes, R-Si(ORâ²)â, generally leads to the formation of... 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....
MRS Proceedings, 2000
Organopolysilsesquioxanes have recently gained much interest as materials for low-K dielectrics [... 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.
MRS Proceedings, 2000
Ring-opening polymerization (ROP) of disilaoxacyclopentanes has proven to be an excellent approac... 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.
MRS Proceedings, 1999
ABSTRACTSol-gel processing of materials is plagued by shrinkage during polymerization of the alko... 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...