Silicon and Aluminum Complexes:
Ion Conducting Polymers
Tech ID: WTC-90-1A
University of Washington researchers have discovered that glycolato silicates
undergo ready ligand exchange with other diols. The use of long chain diols
favors bridging coordination and promotes polymerization to form ionic polymers
containing penta-alkoxy silicate centers. Alternatively, the polymers may be
prepared in one step from SiO2, ethylene glycol, hydroxy-terminated poly
(ethylene oxide), and a group I or group II metal hydroxide or oxide
respectively. These optically transparent polymers are viscous to glassy
materials that exhibit ambient ionic conductivity, good thermal stability, and
cure to hard solids at less than 200 degrees centigrade.
Background:
Solvent-free polymer electrolytes have been highly
sought after for potential use in various electrochemical applications. Use of
poly (ethylene oxide), PEO, to form lithium PEO/siloxyl and PEO/phyllosilicate
solid state electrolytes suggest this to be a fruitful direction for further
work. As penta- and hexa-coordinate silicon glycolates are known to be purely
ionic in character, where the silicon is monoanionic and dianionic respectively,
it was thus reasoned that use of these complexes to form poly (ethylene oxide)
bridging polymers would lead to ion conducting polymers with the anionic silicon
serving as both counterion and crosslinking center.
Description:
These polymers are conveniently prepared either from
the reaction of the corresponding 5- or 6-coordinate glycolato silicate with
tetraethylene glycol (H2PEO4) followed by vacuum distillation, or directly from
SiO2 and a metal oxide or hydroxide in the presence of ethylene glycol and
tetraethylene glycol followed by vacuum distillation, use of BaO). In both
cases, the necessity of high temperature carbothermal reduction of the silicon
prior to functionalization is avoided.
The exact composition of the resulting polymers depends on the extent of
final distillation, and range from viscous liquids to solids, corresponding to
mixtures of mono- and bidentate ligands to fully crosslinked materials. Analysis
shows thermal stability from -70 to +200O C, glass transitions in the -25O C
range, and relatively high conductivities. The anionic, pentacoordinated nature
of the polymers is confirmed by 29Si and 13C NMR.
Applications:
Applications are wide and varied. Demonstrated and
possible use includes:
*Clear polymers capable of conducting current for use in thin layer
applications such as batteries, heated windshields, and electrochromic
glass.
*As a fire retardant. Wood which has been impregnated with these polymers
does not burn.
*As a shock absorbing/damping gel. Polymer viscosity varies with applied
current.
*Has been drawn into fibers for use in fabrics, carpets, or ropes.
*Liquid-crystal polymers stable to 425O C.
*High temperature silicate glasses.
Status:
The synthesis and composition of these ion conducting polymers
are the subject of United States Patent No. 5,440,011. The Washington Research
Foundation is seeking qualified commercial partners capable of developing and
commercializing this technology under license.
For additional information, please contact:
Beth G. Etscheid, Ph.D.
Director of Licensing
Washington Research
Foundation
2815 Eastlake Avenue E, Suite 300
Seattle, WA 98102
Tel:
206.336.5600 Fax: 206.336.5615
betschei@wrfseattle.org
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