Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-07-15
2002-07-23
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S493000
Reexamination Certificate
active
06423770
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to silicate materials comprising silicate domains and one or more substantially nonsilicate domains, in particular to porous silicate materials, a method for fabricating a silicate material, an optical article, a method for fabricating an optical article and a holographic medium.
2. Discussion of the Related Art
Silicate materials with designed porosity have many applications, some of which include applications in the chemical, optical and electronics industries. Porosity is typically introduced by incorporation of surfactant or polymeric templates into sol-gel-like reaction mixtures. The high surface area and specific pore structure of porous silicate materials contribute to their value in chemical separations, sensing, biomaterials, and catalysis. The optical quality of silicates in general suggests their use in fabricating claddings, waveguides, switches, holographic storage media, and other active elements, especially when filled with organic phases. The tunability of the electrical properties of the pores, which in principle can encompass air, solid insulators, semiconductors, metals, or other constituents, makes porous silicates attractive for electronic devices such as low-dielectric constant barriers or high-dielectric constant capacitors. Additionally, porous silicates, when impregnated with photosensitive materials, can serve as media for optical data recording.
It is known to prepare mesoporous silica plates with centimeter-scale lengths and widths and 0.5-mm thickness by codissolving Tetraethoxysilane (TEOS), a resin precursor, with surfactants and excess water in ethanol-heptane, then partially curing and casting the material. Ryong Ryoo et al., Optically Transparent, Single-Crystal-Like Oriented Mesoporous, Silica Films and Plates, J. Phys. Chem. B, Vol. 101, No. 50 (1997). In Ryoo's process some solvent (but probably not all) is removed from the gelling mixture before casting the final shape. No resin is isolated in the process.
It is also known to employ TEOS as a resin precursor with block polyether glycol copolymer templates to form porous fibers and powders. Galen D. Stucky et al., Triblock-Copolymer-Directed Syntheses of Large-Pore Mesoporous Silica Fibers,
Chem. Mater
., Vol. 10, No. 8 (1998).
Thin films have been prepared by using vinyltrimethoxysilane as an additive in a tetramethoxysilane (TMOS)-based precursor mixture. Makoto Ogawa et al., Preparation of Self-Standing Transparent Films of Silica-Surfactant Mesostructured Materials and the Conversion to Porous Silica Films, Adv. Mater., 10, No. 14 (1998). The method described in Ogawa et al. includes dissolving water in a TMOS-based mixture. Some oligomerization of the silicate monomers begins before surfactants are added, but the intermediate resin is not isolated from the volatile byproducts before forming the films.
Other silica materials known in the art include powders templated with nonionic polyethylene oxides and amines, respectively, synthesized from TEOS mixtures (Thomas J. Pinnavaia et al., Unstable Mesostructured Silica Vesicles, Science Vol. 282 (Nov. 13, 1998); Louis Mercier, Direct Sythesis of Functionalized Silica by Non-Ionic Alkylpolyethyleneoxide Surfactant Assembly, Chem. Commun., pp. 1775-1776 (1998)) and gel bioencapsulants, notable for their high glycerol content and low conversion to silicate network, formed by mixing glycerol into a TEOS resin. Iqbal Gill et al., Encapsulation of Biologicals within Silicate, Siloxane, and Hybrid Sol-Gel Polymers. An Efficient and Generic Approach, J. Am. Chem. Soc. 120, pp. 8587-8598 (1998).
It is further known that the “L3” phase formed by a mixture of cetylpyridinium chloride (CPC), hexanol, and water can be used to template the growth of an ordered silicate solid from TMOS. The method provides good optical clarity and pore uniformity, but the solid products are extremely unstable to air, pulverizing spontaneously upon evaporation of volatiles. The curing process requires elevated temperatures (i.e. above room temperature) and long times, and gives products containing no more than 25% silica. K. M. McGrath et al, Formation of a Silicate L
3
Phase with Continuously Adjustable Pore Sizes, Science Vol. 277 pp. 552-555 (1997). Additionally, a procedure for the synthesis of a pre-oligomerized resin from TMOS has been devised. Adachi and Sawai, Japanese Patent No. 07048454 A2 950221 Heisei.
It is advantageous to provide silicate materials with high silicon content that are more stable to annealing, drying and solvent exchange than analogs made from purely monomeric silicates.
It is further advantageous to provide silicate materials that have lower curing temperatures and shorter curing durations than known analogs.
It is also advantageous to provide silicate materials that can be formed into monoliths with thicknesses above 1 mm.
It is also advantageous to provide silicate materials with optimum mechanical strength and optical clarity.
It is further advantageous to provide silicate materials with lessened perturbation of the templating phase during resin cure.
SUMMARY
The invention relates to a silicate material, comprising silicate domains and one or more substantially nonsilicate domains. The material is produced by mixing a templating mixture with a precured resin and preferably one or more resin precursors. The templating mixture preferably comprises one or more surfactants, one or more alcohols and water. A precured resin is formed by reacting one or more silicate resin precursors with water, preferably in the presence of a co-solvent and a catalyst. The precured resin is mixed with the templating mixture and preferably with an additional amount of one or more silicate precursors. Once the material has solidified, solvent may be exchanged within the substantially nonsilicate domains.
The invention also includes a process for producing a silicate material.
The invention further includes an optical article, a method for fabricating an optical article and a holographic medium.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a silicate material comprising silicate domains and one or more substantially nonsilicate domains, in particular to porous silicate materials, a method for fabricating a silicate material, and a holographic method utilizing a silicate material. (“Nonsilicate domains” as used herein shall include “substantially nonsilicate domains”)
The silicate materials of the invention are derived from pre-oligomerized resins, designed for maximum silicon content in the final product. The materials are particularly stable to annealing, drying, and solvent exchange compared to analogs made from purely monomeric silicates. Advantageously, the silicate material can be formed into monoliths with thicknesses greater than about 1 mm. Template and resin compositions and processing conditions can be varied to optimize the structural integrity and optical clarity of the silicate materials. An additional advantage of the invention is believed to be the lessened perturbation of the templating phase during resin cure because of the reduced amount of alcohol-leaving group expelled.
The term silicate, used herein, means a substantially crosslinked network generally derived from tetra-oxygenated silicon species, including , but not limited to, materials that are predominantly silicon oxide. Materials in which trioxygenated silicon is incorporated, such as those derived at least in part from organotrialkoxysilanes, are also considered silicates for the purposes of the invention. Incorporation of other element oxides into silicates, for example, Ge, B, Al, Ti and/or Zr oxides, by incorporation of their precursors into resin precursor mixtures is also within the scope of the invention.
As the volume percent of silicate in the material increases the structural strength increases. It is generally preferred for the silicate domain to comprise greater than about 15 volume percent. However, it is sometimes necessary to balance structural integrity with other desirable
Cain Edward J.
Lucent Technologies - Inc.
Schnader Harrison Segal & Lewis LLP
LandOfFree
Silicate material and process for fabricating silicate material does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Silicate material and process for fabricating silicate material, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Silicate material and process for fabricating silicate material will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2918791