Mechanism and nanosize products of the sol-gel reaction using diphenylsilanediol and 3-methacryloxypropyltrimethoxysilane as precursors

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We use a first-principles calculation and small-angle neutron scattering (SANS) to investigate the mechanism and the nanosize products of the sol-gel reaction with diphenylsilanediol (DPD) and 3-methacryloxypropyltrimethoxysilane (MEMO) precursors in synthesizing a hybrid waveguide material. It is predicted that switching between a DPD hydroxyl and a MEMO methoxy with a reaction rate of 6.8 x 10<SUP>-6 s-1 at 300 K is the fastest process for the first reaction step, thus generating diphenylmethoxysilanol (DPM) and 3-methacryloxypropyldimethoxysilanol (MEDO) as products. However, we determine that this reaction pathway could be modified by the presence of the H</SUP><INF>2</INF><SUP>O released from a catalyst such as Ba(OH)</SUP><INF>2</INF><SUP>.H</SUP><INF>2</INF><SUP>O. Next, switching between the DPM hydroxyl and the MEDO methoxy is followed to generate diphenyldimethoxysilane (DPDM) and 3-methacryloxypropylmethoxysilanediol (MEMDO). However, condensation between a MEMDO hydroxyl and a DPDM methoxy is found to be most favorable for the third reaction step, which generates the DPDM-MEMDO dimer and CH</SUP><INF>3</INF>OH molecule as products. In a similar fashion, a DPDM methoxy of the DPDM-MEMDO dimer can condense with a MEMDO hydroxyl of the second DPDM-MEMDO dimer to increase the chain, but its reaction rate of 2.8 x 10-11 s-1 is predicted to be about 5 times smaller than that between a DPDM methoxy and a MEMDO hydroxyl. This implies that the reaction rate for the larger nanostructures becomes smaller. Additionally, our SANS measurements determine that the final products from our sol-gel reaction are on the nanometer scale, at sizes from 1.76 to 2.36 nm.
Publisher
AMER CHEMICAL SOC
Issue Date
2005-05
Language
English
Article Type
Article
Keywords

ORGANIC-INORGANIC MATERIALS; DENSITY-FUNCTIONAL APPROXIMATION; MOLECULAR-ORBITAL METHODS; OPTICAL WAVE-GUIDES; GAUSSIAN-BASIS SETS; CORRELATION ENERGIES; EXCHANGE-ENERGY; SURFACE; SILICON; DEPOSITION

Citation

JOURNAL OF PHYSICAL CHEMISTRY B, v.109, no.19, pp.9397 - 9403

ISSN
1520-6106
URI
http://hdl.handle.net/10203/18372
Appears in Collection
MS-Journal Papers(저널논문)CBE-Journal Papers(저널논문)EEW-Journal Papers(저널논문)
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