Process for the formation of polyhedral oligomeric silsesquioxanes

Abstract

Three processes for the manufacture of polyhedral oligomeric silsesquioxanes (POSS) which utilize the action of bases that are capable of either attacking silicon or any compound that can react with a protic solvent (e.g. ROH, H2O etc.) and generate hydroxide [OH]−, alkoxide [RO]−, etc. The first process utilizes such bases to effectively redistribute the silicon-oxygen frameworks in polymeric silsesquioxanes [RSiO1.5]∞ where ∞=1−1,000,000 or higher into POSS nanostructures of formulas [(RSiO1.5)n]Σ#, homoleptic, [(RXSiO1.5)n]Σ#, functionalized homoleptic, [(RSiO1.5)m(R′SiO1.5)n]Σ#, heteroleptic, and {(RSiO1.5)m(RXSiO1.0)n}Σ#, functionalized heteroleptic nanostructures. The second process utilizes base to aid in the formation of POSS nanostructures of formulas [(RSiO1.5)n]Σ# homoleptic and [(RSiO1.5)m(R′SiO1.5)n]Σ# heteroleptic and [(RSiO1.5)m(RXSiO1.0)n]Σ# functionalized heteroleptic nanostructures from silanes RSiX3 and linear or cyclic silsesquioxanes of the formula RX2Si—(OSiRX)m—OSiRX2 where m=0-10, X═OH, Cl, Br, I, alkoxide OR, acetate OOCR, peroxide OOR, amine NR2, isocyanate NCO, and R. The third process utilizes base to selectively ring-open the silicon-oxygen-silicon (Si—O—Si) bonds in POSS structures to form POSS species with incompletely condensed nanostructures. These processes also afford stereochemical control over X. The three processes result in new POSS species that can undergo additional chemical manipulations to ultimately be converted into POSS-species suitable for polymerization, grafting, or other desirable chemical reactions.

Description

RELATED APPLICATIONS [0001] This application is: a continuation of U.S. patent application Ser. No. 09 / 631,892 filed Aug. 14, 2000 (which claims priority from U.S. Provisional Patent Application Ser. No. 60 / 147,435, filed Aug. 4, 1999); a continuation of U.S. patent application Ser. No. 10 / 351,292, filed Jan. 23, 2003 (which claims priority from U.S. Provisional Patent Application Ser. No. 60 / 351,523, filed Jan. 23, 2002), which is a continuation-in-part of U.S. patent application Ser. No. 09 / 818,265, filed Mar. 26, 2001, now U.S. Pat. No. 6,716,919 (which claims priority from U.S. Provisional Patent Application Ser. No. 60 / 192,083, filed Mar. 24, 2000); a continuation of U.S. patent application Ser. No. 09 / 747,762, filed Dec. 21, 2000 (which claims priority from U.S. Provisional Patent Application Ser. No. 60 / 171,888, filed Dec. 23, 1999); and a continuation of U.S. patent application Ser. No. 10 / 186,318, filed Jun. 27, 2002 (which claims priority from U.S. Provisional Patent Appli...

AI Technical Summary

Benefits of technology

[0021] The purpose of the base is to cleave the silicon-oxygen-silicon (Si—O—Si) bonds in the various silsesquioxane structures. The exact type of base, its hydration sphere, concentration, and solvent interactions all play important roles in the effectiveness of the base for cleaving the silicon-oxygen bonds. Proper understanding and control of conditions enable the selective cleavage and / or assembly of silsesquioxane, silicate, POSS, and POSS fragment systems in the desired manner. The base can also assist in the assembly of POSS fragments.

[0026] The current methods of preparing POSS molecules from the acid catalyzed condensation of alkyltrichlorosilanes (RSiCl3) is inefficient in that it produces mixtures of POSS cage species homoleptic (POSS) [(RSiO1.5)n]Σ#, functionalized homoleptic POSS [(RSiO1.5)m(RXSiO1.0)n]Σ#, heteroleptic POSS [(RSiO1.5)m(RSiO0.5)n]Σ#, functionalized heteroleptic POSS [(RSiO1.5)m(RXSiO1.0)n]Σ# and polymeric silsesquioxanes [RSiO1.5])∞. In some cases the undesired polymeric silsesquioxanes are produced in as much as 75% yield. It is therefore advantageous to develop a process that can efficiently convert [RSiO1.5]∞ into desirable POSS nanostructures or into POSS fragments [(RXSiO1.5)n]. Such a process will serve to not only reduce the amounts of hazardous waste produced in such reactions but will also reduce the production costs for POSS systems.

[0029] We have found that hydroxide [OH]− bases are highly effective at concentrations of 1-equivalents (the preferred range is 2-5 equivalents per silicon atom) per mole of silicon for the conversion of aliphatic and aromatic polysilsesquioxanes [RSiO1.5]∞ into homoleptic (POSS) [(RSiO1.5)n]Σ#, functionalized homoleptic POSS [(RSiO1.5)m(RXSiO1.0)n]Σ# heteroleptic POSS [(RSiO1.5)m(R′SiO1.5)n]Σ#, and functionalized heteroleptic POSS [(RSiO1.5)m(R′SiO1.5)n(RXSiO1.0)p]Σ#. Hydroxyl-bases are particularly effective for producing [(RSiO1.5)m(RXSiO1.0)n]Σ# POSS species. We have found that milder bases such as acetate and carbonate are more effective at converting [RSiO1.5]∞ systems bearing vinyl or allyl groups. It is also recognized that the use of other co-reagents may be used to promote the formation of POSS species from this process.

[0038] The first example in Scheme 3 illustrates the selectivity for the cleavage of 6 membered silicon-oxygen rings in the presence of 8 membered silicon-oxygen rings by the base, to afford the trifunctionalized POSS species. This reaction is driven by the release of greater ring strain energy from the cleavage of the 6 membered silicon-oxygen ring vs. cleavage of the 8 membered silicon-oxygen ring and is thermodynamically favorable. In the second example the energy of the twisted conformation is relieved upon cleavage to form a more open structure.

[0043] This processes utilizes bases (as defined previously) and POSS nanostructures having homoleptic [(RSiO1.5)n]Σ# and heteroleptic [(RSiO1.5)m(R′SiO1.5)n]Σ# compositions. The process allows for the conversion of low cost and easily produced unfunctionalized POSS nanostructures into more desirable functionalized POSS systems of the type [(RSiO1.5)m(RXSiO1.0)n]Σ# POSS nanostuctures of the type [(RSiO1.5)m(RXSiO1.0)n]93 # can be used as stand alone chemical reagents or further derivatized to provide a diverse array of other POSS nanostructures. This process provides an entirely new synthetic route for the preparation of very important and useful incompletely condensed trisilanol reagents [(RSiO1.5)4(RXSiO1.0)3]Σ7 in particular where X═OH.

Problems solved by technology

In most cases, however, hydrolytic condensation reactions of trifunctional organosilicon monomers afford complex polymeric resins and POSS molecules that are unsuitable for use in polymerization or grafting reactions because they do not possess the desired type or degree of reactive functionality.

While these methods are highly useful for varying the organic functionality (substituents) contained on POSS molecules they are not always amenable to low-cost manufacturing nor do they offer the ability to selectively cleave and or manipulate the silicon-oxygen frameworks of such compounds.

Thus, these methods are of no utility for transforming the multitude of readily available and low cost silane, silicate, polysilsesquioxane (aka T-resins or T-type siloxanes) or POSS systems.

While there is precedent in the literature for treatment of silsesquioxanes and POSS systems with base, the previous art does not afford the selective manipulation of silicon-oxygen frameworks and the subsequent controlled production of POSS fragments, homoleptic POSS nanostructures, heteroleptic POSS nanostructures and functionalized heteroleptic POSS nanostructures.

Furthermore, the prior art does not provide methods of producing POSS systems suitable for functionalization and subsequent polymerization or grafting reactions.

Additionally the prior art does not demonstrate the action of bases on silane, silicate, or silsesquioxane feedstocks suitable for producing low-cost and high purity POSS systems.

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