Cubic octameric silsesquioxanes, because of their octahedral structures and nanometer size, repre... more Cubic octameric silsesquioxanes, because of their octahedral structures and nanometer size, represent potentially very useful nanoconstruction sites. Here we report the reaction of octaaminophenylsilsesquioxane (OAPS) with a variety of epoxides and dianhydrides and their subsequent heat treatment to form nanocomposite films with exceptional oxygen barrier properties. While solution-cast films give relatively low oxygen transmission rates (OTR), casting followed by warm-pressing lowers the OTR to values competitive with commercially available high-performance barrier films. The lowest OTR measured was obtained with a warm-pressed bilayer films consisting of OAPS/tetraglycidyl-m-xylenediamine and OAPS/2,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate with OTRs 500 °C when fully cured), making them ideal for electronics packaging and encapsulation applications.
... R. Tamaki, § S.-G. Kim, MZ Asuncion, M. Roll, T. Nemoto, Y. Ouchi, Y. Chujo, and RM L... more ... R. Tamaki, § S.-G. Kim, MZ Asuncion, M. Roll, T. Nemoto, Y. Ouchi, Y. Chujo, and RM Laine* . ... Abstract. Poly(bromooctaphenylsilsesquioxane)s (Br x OPS) are easily synthesized from octaphenylsilsesquioxane (OPS) via bromination with Br 2 /Fe in dichloromethane. ...
Page 1. ORIGINAL PAPER Perfect and nearly perfect silsesquioxane (SQs) nanoconstruction sites and... more Page 1. ORIGINAL PAPER Perfect and nearly perfect silsesquioxane (SQs) nanoconstruction sites and Janus SQs RM Laine Æ M. Roll Æ M. Asuncion Æ S. Sulaiman Æ V. Popova Æ D. Bartz Æ DJ Krug Æ PH Mutin Received ...
Rice hull ash (RHA) silica (80–98 wt.% amorphous, >25 m2 g−1 silica, 2–20% porous amorphous C)... more Rice hull ash (RHA) silica (80–98 wt.% amorphous, >25 m2 g−1 silica, 2–20% porous amorphous C) can be depolymerized in aqueous alcohol with [NR4]8OH (R = Me, CH2CH2OH) under ambient conditions with the selective formation of octasilicate anions, [NR4]8[OSiO1.5]8. Dissolution kinetics were studied as a function of base and water concentration and temperature. Dissolution rates were determined by conversion of the octaanion to [HMe2OSiO1.5]8, OHS. Activation energies for dissolution were 5 ± 1 kcal mol−1, much lower than for typical base-promoted silica dissolution. Furthermore, dissolution was not catalytic in base as found for other base-promoted silica dissolution reactions. Reaction rates were dependent on ammonium base and water concentrations and temperature. Dissolution was optimal at approximately one equivalent of [NR4]8OH and three equivalents of water for choline hydroxide and five equivalents of water for [NMe4]8OH. A single crystal study of the octacholine [Me3NCH2CH2OH]8 derivative indicates that the compound crystallizes with three equivalents of water per SiO1.5 suggesting that the rate limiting step in the dissolution process may be formation of the octaanion which is in accord with theoretical Ea’s calculated for the condensation of polyhydroxyl siloxanes. Octasilicate anions offer access to novel polyfunctional silsesquioxane platforms with each functional group occupying a single octant in Cartesian space. These platforms offer potential as precursors to dendrimers and hyperbranched polymers, and as nanobuilding blocks for the formation of nanocomposites. Furthermore, choline is structurally similar to: (1) e-N,N,N-trimethyl-γ-hydroxy-lysine, (2) the oligomeric N-methylpropylamine components found in silafins, and (3) possibly the hydroxyamino acid units found in sponge filament proteins; all of which are thought to play a role in silica accretion, transport and deposition in diatoms and sponges. Thus, the octasilicate structure may reflect the structure(s) of species involved in silica transport and/or deposition in biosilicification processes.
The cubic symmetry of octafunctional octaphenylsilsesquioxanes [ROPS, (RC6H4SiO(1.5))8] coupled w... more The cubic symmetry of octafunctional octaphenylsilsesquioxanes [ROPS, (RC6H4SiO(1.5))8] coupled with a 1 nm diameter offers exceptional potential to assemble materials in three dimensions with perfect control of periodicity and the potential to tailor global properties at nanometer length scales. OPS itself is very inert and insoluble and can only be functionalized via electrophilic reactions with difficulty and with poor substitutional selectivity. However, functionalized OPS products are robust and highly soluble, offering easy purification and processing. In contrast to previous studies, we report here that OPS reacts with ICl at sub-ambient temperatures to provide (following recrystallization) [p-IC6H4SiO(1.5)]8, or I8OPS, in good yields and with excellent selectivity: >99% mono-iodo substitution with >93% para substitution as determined by H2O2/F- cleavage of the Si-C bonds to produce iodophenols. I8OPS in turn can be functionalized using conventional catalytic coupling reactions to provide sets of >93% para-substituted, functionalized compounds (alkynes, alkenes, aryl amines, phosphonates, aryl amines, polyaromatics, etc.), suggesting the potential to develop diverse nano-building blocks for the assembly of a wide variety of materials, some with novel photonic, electronic, and structural properties.
Cubic octameric silsesquioxanes, because of their octahedral structures and nanometer size, repre... more Cubic octameric silsesquioxanes, because of their octahedral structures and nanometer size, represent potentially very useful nanoconstruction sites. Here we report the reaction of octaaminophenylsilsesquioxane (OAPS) with a variety of epoxides and dianhydrides and their subsequent heat treatment to form nanocomposite films with exceptional oxygen barrier properties. While solution-cast films give relatively low oxygen transmission rates (OTR), casting followed by warm-pressing lowers the OTR to values competitive with commercially available high-performance barrier films. The lowest OTR measured was obtained with a warm-pressed bilayer films consisting of OAPS/tetraglycidyl-m-xylenediamine and OAPS/2,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate with OTRs 500 °C when fully cured), making them ideal for electronics packaging and encapsulation applications.
... R. Tamaki, § S.-G. Kim, MZ Asuncion, M. Roll, T. Nemoto, Y. Ouchi, Y. Chujo, and RM L... more ... R. Tamaki, § S.-G. Kim, MZ Asuncion, M. Roll, T. Nemoto, Y. Ouchi, Y. Chujo, and RM Laine* . ... Abstract. Poly(bromooctaphenylsilsesquioxane)s (Br x OPS) are easily synthesized from octaphenylsilsesquioxane (OPS) via bromination with Br 2 /Fe in dichloromethane. ...
Page 1. ORIGINAL PAPER Perfect and nearly perfect silsesquioxane (SQs) nanoconstruction sites and... more Page 1. ORIGINAL PAPER Perfect and nearly perfect silsesquioxane (SQs) nanoconstruction sites and Janus SQs RM Laine Æ M. Roll Æ M. Asuncion Æ S. Sulaiman Æ V. Popova Æ D. Bartz Æ DJ Krug Æ PH Mutin Received ...
Rice hull ash (RHA) silica (80–98 wt.% amorphous, >25 m2 g−1 silica, 2–20% porous amorphous C)... more Rice hull ash (RHA) silica (80–98 wt.% amorphous, >25 m2 g−1 silica, 2–20% porous amorphous C) can be depolymerized in aqueous alcohol with [NR4]8OH (R = Me, CH2CH2OH) under ambient conditions with the selective formation of octasilicate anions, [NR4]8[OSiO1.5]8. Dissolution kinetics were studied as a function of base and water concentration and temperature. Dissolution rates were determined by conversion of the octaanion to [HMe2OSiO1.5]8, OHS. Activation energies for dissolution were 5 ± 1 kcal mol−1, much lower than for typical base-promoted silica dissolution. Furthermore, dissolution was not catalytic in base as found for other base-promoted silica dissolution reactions. Reaction rates were dependent on ammonium base and water concentrations and temperature. Dissolution was optimal at approximately one equivalent of [NR4]8OH and three equivalents of water for choline hydroxide and five equivalents of water for [NMe4]8OH. A single crystal study of the octacholine [Me3NCH2CH2OH]8 derivative indicates that the compound crystallizes with three equivalents of water per SiO1.5 suggesting that the rate limiting step in the dissolution process may be formation of the octaanion which is in accord with theoretical Ea’s calculated for the condensation of polyhydroxyl siloxanes. Octasilicate anions offer access to novel polyfunctional silsesquioxane platforms with each functional group occupying a single octant in Cartesian space. These platforms offer potential as precursors to dendrimers and hyperbranched polymers, and as nanobuilding blocks for the formation of nanocomposites. Furthermore, choline is structurally similar to: (1) e-N,N,N-trimethyl-γ-hydroxy-lysine, (2) the oligomeric N-methylpropylamine components found in silafins, and (3) possibly the hydroxyamino acid units found in sponge filament proteins; all of which are thought to play a role in silica accretion, transport and deposition in diatoms and sponges. Thus, the octasilicate structure may reflect the structure(s) of species involved in silica transport and/or deposition in biosilicification processes.
The cubic symmetry of octafunctional octaphenylsilsesquioxanes [ROPS, (RC6H4SiO(1.5))8] coupled w... more The cubic symmetry of octafunctional octaphenylsilsesquioxanes [ROPS, (RC6H4SiO(1.5))8] coupled with a 1 nm diameter offers exceptional potential to assemble materials in three dimensions with perfect control of periodicity and the potential to tailor global properties at nanometer length scales. OPS itself is very inert and insoluble and can only be functionalized via electrophilic reactions with difficulty and with poor substitutional selectivity. However, functionalized OPS products are robust and highly soluble, offering easy purification and processing. In contrast to previous studies, we report here that OPS reacts with ICl at sub-ambient temperatures to provide (following recrystallization) [p-IC6H4SiO(1.5)]8, or I8OPS, in good yields and with excellent selectivity: >99% mono-iodo substitution with >93% para substitution as determined by H2O2/F- cleavage of the Si-C bonds to produce iodophenols. I8OPS in turn can be functionalized using conventional catalytic coupling reactions to provide sets of >93% para-substituted, functionalized compounds (alkynes, alkenes, aryl amines, phosphonates, aryl amines, polyaromatics, etc.), suggesting the potential to develop diverse nano-building blocks for the assembly of a wide variety of materials, some with novel photonic, electronic, and structural properties.
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Papers by Michael vincent Asuncion