The present disclosure relates to methods for making and optimizing functionalized silsesquioxane/siloxane chemical and/or physical mixtures to tailor their properties for use in forming coatings and monoliths for specific mechanical, photonic and/or electronic applications.
This section provides background information related to the present disclosure which is not necessarily prior art. Silicone resins are used in numerous applications ranging from sealing kitchen and bathroom surfaces, to soft contact lenses, to novel antireflective coatings, to low dielectric constant materials for interlayer dielectrics in multilayer integrated chip manufacturing to name just a few.
They are formulated using a wide variety of components and chemistries that typically involve the hydrolysis of various components RSiX3 (X═Cl, OR′, OAc), R2SiCl2, and R3SiCl in selected ratios (where R═H, CH3, Et, propyl, CH2CH2CF3, CH2CH2CH2Cl, CH2CH2CH2SH, CH2CH2CH2NH2, CH2CH═CH2, CH═CH2, phenyl for example). SiCl4 can also be added.
The purpose of the hydrolysis of these mixtures is to tailor the properties of the resulting material or material precursor to those needed for a specific application. The hydrolysis process often results in the production of unwanted, toxic and polluting HCl if X═Cl, which must be removed. In many instances, species like HSiMe2 or [-MeHSi—O]x- are added so that in a second or third step, hydrosilylation can be used to further tailor the properties of the material or material precursor as suggested in reactions (1) and (2) [R=phenyl] in
Once formulated, these systems cannot be modified for example to add more [-Me2SiO—], RSiO1.5 (T or SQ) or RMe2Si—O—SiO1.5 (Q) units or to add more or different CH2CH2R groups. Furthermore, these compounds are typically oligomeric resins with molecular weights of a few hundreds to thousands or even millions of Daltons. Once formed it is quite difficult to manipulate their inherent viscosities or adhesive properties or their thermal stabilities. Finally there is no indication in the literature that they can be recycled.
We have discovered a simple catalyst system that can be used to form families of silsesquioxane (RSiO1.5=SQ)/Q (RMe2Si—O—SiO1.5=Q)/siloxane/systems starting from a wide variety of SQ cages or resins, Q cages or resins, alkoxysilane monomers, such that the properties of the resulting SQ/Q/siloxane system can be tailored to give recyclable SQ/Q/siloxane resins and or simple cage-like SQ/Q/siloxane oligomers. The properties of these materials or material precursors can be tailored over a wide range by simple choice of the overall composition of the starting components. Furthermore, they can be modified after formation to adjust their properties incrementally or extensively.
The resulting monomer units and/or resin systems can be used to form novel coatings or monolithic materials with high thermal and environmental stability, controlled hardness, refractive index, transparency, toughness, degree of hydrophobicity/hydrophilicity, adhesion to specific surfaces and the potential to be photolytically and/or chemically crosslinked for example. In instances where the compounds are not extensively covalently crosslinked with complex carbon-carbon bond interactions, the coatings and/or monoliths can be redissolved and recycled or modified in the original solvent in the presence of the initial catalyst despite exposure to temperatures exceeding 250° C.
All of these possibilities arise because of the use of simple and harmless fluoride (F−) catalysts. We have discovered that silicon centers in silicone resins, SQ and Q cages, even those with very poor solubility, will dissolve in most organic solvents (acetone, toluene, ether, THF) in the presence of sometimes less than 1% of an ammonium fluoride. Two such fluorides are [(CH3)4NF] and {[(CH3)3C]4NF} called for short TMAF and TBAF.
Apparently, in the presence of the fluoride ion, F−, the silicon-oxygen bonds are cleaved and reformed at great rates even at ambient temperature. The most general description of the synthesis process of the present invention is given in
The novelty of the invention is seen based on selected background literature. Thus, for example Bassindale et al discovered that it is possible to hydrolyze alkoxysilanes using F− sources at nearly molar amounts of F− to produce cage compounds in low 5-40% yields (reaction 3 in
This is similar to the yields seen in reaction (3). In contrast, we have concluded that F− itself is the true catalyst and does not act as a base. We also find that F− can be used in as little as 0.25 mol % to effect the same reactions. Furthermore, according to References 3 to 5, we find that by removing the F− from solution we can obtain the same vinyl T10 and vinyl T12 in quantitative (100%) yields.3-5 Reference 5 is U.S. Patent Application R. M. Laine, S. Sulaiman, “Properties tailoring in silsesquioxanes via a novel inter-conversion processes,” U.S. Patent to R. M. Laine, S. Sulaiman, “Properties tailoring in silsesquioxanes via a novel inter-conversion processes,” U.S. Pat. No. 8,053,514, Nov. 8, 2011 which we incorporate herein as prior art.
What is not evident in the above prior art and is not obvious to someone of average skill (bachelors degree in chemistry and two years training in silicon chemistry) is that it is possible to coincidentally use mixtures of a wide variety of SQ and Q resins, cages, siloxanes, and/or alkoxysilanes (acetoxy, propanoxy, etc) to produce a very wide variety of new resin or cage systems simply by using catalytic amounts of a soluble F− source with trace amounts of water that can be left in to give resins of the composition of the starting component functionalities or to remove this F− source to produce mixed functionality cage systems with the same compositions. Some examples of the types of cage systems that we have identified can be produced are seen in Examples 2-5.
We submit that it is not obvious that PDMS and cyclic siloxanes will mix and equilibrate with Tn cages or resins nor is it obvious that Q8,10 cages or resins can also be introduced. We submit that Si—H bonds are likely to react to trap F− as Si—F bonds. We also suggest that the fact that Si—F bonds in some instances may form in the catalytic process and despite their having one of the highest bond energies know for common elements can also be displaced and this is one possible mechanism whereby the catalytic exchange processes take place.
a and 5b show monoliths, thin films and coatings of OPS/MeD4 T-resins according to the present invention, wherein FIG. 5a shows 1:1 OPS/MeD4 cast and air hardened and
a and 6b show the use of a refractive index matched OPS/Me8D4/S-fiber glass system that gives a transparent composite after casting and curing by heating mildly to temperatures between 10° and 300° C., according to the present invention, wherein
a to 8c show examples of hydrophobicity of OPS/MeD4 coatings according to the present invention, wherein
a to 9c show additional examples of hydrophobicity of OPS/MeD4 coatings according to the present invention, wherein
a to 10d show examples of corrosion resistance of OPS/MeD4 coatings according to the present invention, wherein
a and 12b show that 5-20 mol % [vinylSiO1.5]10/12—[HSCH2CH2CH2SiO1.5]n mixtures undergo rapid, ambient F− catalyzed exchange with OPS/MeD4 introducing controlled compositions, according to the present invention, wherein
Using the subject invention, we have extended this work finding that mixtures of 5-70 mol % OPS, (PhSiO1.5)8 copolymerize with octamethylcyclotetrasiloxane (MeD4) using 0.25-2 mol % F− to form random-structured SQ “T-resin siloxanes copolymers or resins” with stoichiometric control of phenyl:methyl ratios (
Highly insoluble OPS dissolves in acetone or THF after stirring at RT for 2 h. This is very unusual because neither OPS nor the Me8D4 are normally soluble in acetone let alone at RT. Low mol % OPS (high mol % MeD4) films, monoliths or coatings are transparent, flexible, and soft while the opposite ratios give transparent, rigid, and hard films, monoliths or coatings. Retaining the F− (levels less than in toothpaste) leads exclusively to SQ resins with mixed functionalities (see below) without unreacted “monomers” in a “one-pot” route at ambient in 2-48 h. Alternatively, trapping the F− provides mixed functional cages.
The species that form in solutions from the reaction of
Monoliths, thin films and coatings of OPS/MeD4 T-resins (
a shows 1:1 OPS/MeD4 cast and air hardened and
These same compounds can be used to cast and index match glass fibers thus,
a shows 2-plies of S-glass and
As noted above, despite heating to temperatures greater than or equal to 200° C., the presence of small amounts (0.05% w/w) of catalytic F− remaining in the polymer upon hardening also allows the coatings to be recycled and/or repaired. The matrix of the composite shown in
OPS/MeD4 coatings are also hydrophobic. Dip- or spray coated glass on marine-grade Al 5083 offer water contact angles of 90-95° , as shown in
As mentioned above, nanoparticles may be added to the coating system to introduce surface roughness to the substrate, resulting in a superhydrophobic surface. Similarly OPS/[Me(CF3CH2CH2)SiO]4 coatings (or other partially or fully fluorinated siloxanes, Rf-alkoxysilanes etc) on silica cores with rough surfaces give water contact angles >155° (
2:3 mol % OPS/MeD4 coatings on glass in
As shown
OPS/RD4-type systems harden as a random network without free monomer, and are thus expected to form smooth, void-free surfaces unless nanoparticles are specifically added that are unlikely to physically collect rust or biofoul as it is also well known that biorganisms do not settle easily on smooth or superhydrophobic (added nanoparticles) surfaces.
Corrosion studies performed using standard Mil-Spec methods show that the addition of rare earth oxides of cerium and zirconium gave much improved corrosion resistance. When added to OPS/MeD4 coatings it greatly increases the corrosion resistance of A15083 with <1 wt % of the rare earths thus keeping costs low.
a shows OPS/MeD4 with rare earth corrosion inhibitor on Al 5083 after 200 h corrosion test,
Thermogravimetric analysis shows that the coatings or monoliths decompose without melting above 400° C., indicative of true thermosetting materials. Traditional thermosets are typically recycled as fillers (by physically shredding and/or grinding) or thermally or chemically broken down into monomers, though at the expense of high energy or prohibitive chemical costs. In contrast, OPS/MeD4 coatings, dissolve readily in a small amount of suitable solvent in 4-8 h. In addition, spray coating or brush-on of additional material should easily address repairs to damaged coatings. The ease of this process should allow in service repairs. Finally, as a point for comparison, the amount of F− in toothpaste (as NaF) in the U.S. is typically 0.22-0.24% w/w or about 5× more concentrated than for our systems.
Further functionality can be introduced if OPS/MeD4 systems are reacted with other functionalized SQs including for example RHA-derived “Q8” octaglycidyl (OG) SQs (see Scheme 1, Q system where R=Glycidyl) via F− catalyzed exchange, providing resins with reactive sites for further crosslinking, i.e. with amines. High crosslink densities give OG/amine (e.g. OAPS, octaminophenyl SQ) resins high strength (E=2.4-3.5 GPa) and fracture toughness (K1c=1.8). Similarly, methylacrylate and even vinyl and SH groups can be introduced using F− catalysis. Thus HS(CH2)3Si(OCH2CH3)3, or [HSCH2CH2CH2SiO1.5]n can be used to form analogous -SH cages as suggested in
We recently discovered that 5-20 mol % [vinylSiO1.5]10/12-[HSCH2CH2CH2SiO1.5]n mixtures (
As shown in
In general, this basic polymer system can be modified in multiple ways to add crosslink density to soft materials to introduce greater toughness and tear strength. Other moieties can be added to tailor resistance to adhesion by marine organisms (e.g. introducing a variety of radical traps including dibutyl phenols, EDTA, TEMPO, etc.) to disrupt crosslinking mechanisms to Al, for example, SQ resins are also resistant to typical solvents and changes in pH; their high abrasion resistance (hardnesses to 2.5 GPa) should imbue compatibility with shipboard cleaning regimens, likely reducing the time/effort involved in cleaning and ultimately extending coating lifetimes.
Thus, it is possible to make mixed thiol-vinyl SQ/siloxane systems that will self cure using ene-thiol reactions where both the ene (vinyl) and the thiol are introduced to the same molecules at temperatures where the ene-thiol reaction will not proceed. These materials are thermoset systems that do not off-gas anything. Alternately, they can be crosslinked photolytically. It is also important to note that these systems can be made to be liquids or low melting solids such that they can be cast or coated without solvents.
Thus, OPS/RD4-resin/Q and cage systems provide access to novel, inexpensive, and multifunctional coatings with tailorable mechanical and hydrophobic surface properties currently not accessible with most types of coating systems. Two routes (via addition of modified D4 or other SQs or Qs) permit introducing other functional groups e.g. vinyl and SH groups to improve mechanical properties and/or chemical compatibility or abrasion resistance or resistance to UV aging etc.
The following examples are used in support of this invention.
Synthesis of Mixed Phenyl:Me (10:1) Silsesquioxane Resins. Octaphenylsilsesqui-oxane [OPS, 10.00 g, 9.7 mmol (77.4 mmol phenyl)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (200 mL) was added and the mixture stirred for 5 mins. Octamethylcyclotetrasiloxane [MeD4, 0.33 mL, 1.08 mmol (8.64 mmol CH3)] was added via syringe followed by 2.0 mL TBAF (2.0 mmol). The reaction mixture was stirred for 2 d at RT until the reaction mixture turned clear. The insolubles were then gravity filtered and the filtrate was removed under reduced pressure to give a viscous clear liquid (9.60 g, 93% with respect to total initial mass of reactants). IR: υC═H (3073-3006), υC—H (2961-2905), υC═C (Ar ring, 1594), υC═C (Ar ring, 1430), υSi—CH3 (1259) υSi—O (1131-1011), υSi—CH3 (841), υSi—C (796) cm−1.
Synthesis of Mixed Phenyl:Me (1:10) Silsesquioxane Resins. OPS [3.48 g, 3.37 mmol (27.0 mmol phenyl)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (200 mL) was added and the mixture stirred for 5 mins. MeD4 [10.45 mL, 33.7 mmol (270.0 mmol CH3)] was added via syringe followed by 2.0 mL TBAF (2.0 mmol). The reaction mixture was stirred for 2 d at RT until the reaction mixture turned clear. The insolubles were then gravity filtered and the filtrate was removed under reduced pressure to give a viscous clear liquid (13.05 g, 97% with respect to total initial mass of reactants). IR: υC═H (3073-3006), υC═H (2961-2905), υC═C (Ar ring, 1594), υC═C (Ar ring, 1430), υSi—CH3 (1259) υSi—O (1131-1011), υSi—CH3 (841), υSi—C (796) cm−1.
Identification of the structures is presented in Example 3. Table of values here (None have Ag+) all straight cages.
Synthesis of Mixed Phenyl:Me (1:1) Silsesquioxane Resins. OPS [34.80 g, 33.7 mmol (270.0 mmol phenyl)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (200 mL) was added and the mixture stirred for 5 mins. MeD4 [10.45 mL, 33.7 mmol (270.0 mmol CH3)] was added via syringe followed by 2.0 mL TBAF (2.0 mmol). The reaction mixture was stirred for 2 d at RT until the reaction mixture turned clear. The insolubles were then gravity filtered and the filtrate was removed under reduced pressure to give a viscous clear liquid (42.55 g, 95% with respect to total initial mass of reactants). TGA (air, 1000° C.): found 23.7%; Td5%=358° C. IR: υC═H (3073-3006), υC═H (2961-2905), υC═C (Ar ring, 1594), υC═C (Ar ring, 1430), υSi—CH3 (1259) υSi—O (1131-1011), υSi—CH3 (841), υSi—C (796) cm−1.
MALDI-ToF mass spectral analysis of this reaction solution shows the pattern shown in
Synthesis of Mixed Phenyl:Me:CF3CH2CH2— (6.5:5:1) Silsesquioxane Resins. OPS [26.11 g, 25.3 mmol (202.4 mmol phenyl)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (200 mL) was added and the mixture stirred for 5 mins. MeD4 [4.71 mL, 15.2 mmol (121.6 mmol CH3)] and (3,3,3-trifluoro-propyl)methylcyclo-trisiloxane [3.94 mL, 10.4 mmol (31.2 mmol -CH2CH2CF3) was added via syringe followed by 2.0 mL TBAF (2.0 mmol). The reaction mixture was stirred for 2 d at RT until the reaction mixture turned clear. The insolubles were then gravity filtered and the filtrate was removed under reduced pressure to give a viscous clear liquid (33.4 g, 94% with respect to total initial mass of reactants). IR: υC═H (3073-3006), υC═H (2961-2905), υC═C (Ar ring, 1594), υC═C (Ar ring, 1430), υSi—CH3 (1259), υC-F (1209), υSi—O (1131-1011), υSi—CH3 (841), υSi—C (796) cm−1.
NMR analysis of the reaction solution gives the spectra shown in
13C NMR shows peaks in the 120-136 ppm aromatic C region. Peaks at 13-19 are for aliphatic carbons. The MALDI-ToF mass spectral analysis of this reaction solution shows the pattern shown in
The various peaks in the Mass spectrum are easily analyzed and the suggested structures shown in
Note that the mass spectral analyses can be off by one to two units due to the presence of water, different isotopes of Ag+.
These structures are unique and have never been seen before and represent new chemical compounds in equilibrium with polymeric versions of these compounds that form when the solvent is concentrated.
Synthesis of Mixed Phenyl:Methacrylate (1:1) Silsesquioxane Resins. OPS [10.00 g, 9.7 mmol (77.4 mmol phenyl)] and octa[(methacryloylpropyl)dimethylsilyloxy] silses-quioxane [OMPS, 19.66 g, 9.7 mmol (77.4 mmol methacrylate)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (200 mL) was added and the mixture stirred for 5 mins. TBAF (2.0 mL, 2.0 mmol was added via syringe and the reaction mixture was stirred for 7 d at RT until the reaction mixture turned clear. The insolubles were then gravity filtered and the filtrate was removed under reduced pressure to give a viscous clear liquid (27.0 g, 91% with respect to total initial mass of reactants). IR: υC═H (3073-3006), υC═H (2956-2882), υC═O (1733), υC═C (Ar ring, 1430), υSi—CH3 (1253) υSi—O (1132-1047), υSi—CH3 (839), υSi—C (780) cm−1.
OG/Cyclohexanethioether-T10/12 (9:1) Rearrangement. OG (10.0 g, 5.179 mmol) and cyclohexanethioether-T10/12 (0.8993 g, 0.4187 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of tetrahydrofuran (THF, 1.233 mol) to achieve a ratio of 1 sulfur eq per 9 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Hexylthioether-T (9:1) Rearrangement. OG (10.0 g, 5.179 mmol) and hexylthioether-T (0.9085 g, 0.4185 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 9 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Cyclohexanethioether-T (1:1) Rearrangement. OG (2.5 g, 1.295 mmol) and cyclohexanethioether-T (2.0236 g, 0.9415 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 1 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h.
This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Hexylthioether-T (1:1) Rearrangement. OG (5.0 g, 2.590 mmol) and hexylthioether-T (4.0883 g, 1.883 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 1 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Cyclopentanethioether-T (1:1) Rearrangement. OG (5.0 g, 2.590 mmol) and cyclopentanethioether-T (3.7561 g, 1.883 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 1 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Octylthioether-T (1:1) Rearrangement. OG (5.0 g, 2.590 mmol) and octylthioether-T (4.6696 g, 1.883 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 1 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
OG/Butylthioether-T10/12 (1:1) Rearrangement. OG (5.0 g, 2.590 mmol) and butylthioether-T10/12 (3.5073 g, 1.883 mmol) were added to a 250 ml round bottom flask and dissolved in 100 ml of THF (1.233 mol) to achieve a ratio of 1 sulfur eq per 1 epoxide eq. The flask was then equipped for magnetic stirring and plugged with a septum. Then, 2.0 ml of TBAF (1 M in THF, 6.785 mmol) was added via syringe. The reaction was stirred at RT for 24 h. Then, the solution was split into two samples. The THF from one sample was removed by rotary evaporation and further dried under vacuum at RT for 16 h. This sample still contained F—. The second sample was stirred with CaCl2 (2.0 g, 18 mmol) for 24 h to capture the F—. The insoluble solid was filtered off. THF from the filtrate was removed by rotary evaporation and the product was further dried under vacuum at RT for 24 h.
Synthesis of Mixed [PhenylSiO1.5]8:[Me3SiOSiO1.5]8 (1:1) Silsesquioxane Q resins. OPS [3.80 g, 3.3 mmol (2.7 mmol phenyl)] was added to a dry 250 mL round bottom flask equipped with magnetic stirrer. THF (50 mL) was added and the mixture stirred for 5 mins. [Me3SiOSiO1.5]8 [3.38, 3.0 mmol] was added via syringe followed by 2.0 mL TBAF (2.0 mmol). The reaction mixture was stirred for 2 d at RT until the reaction mixture turned clear. MALDI-ToF mass spectral analysis of this reaction solution shows the following pattern. Although equal amounts of phenyls are introduced the ionizable species favor products with more Me3SiOSiO1.5 components. The suggested structures for a number of peaks are presented in
Note that in all cases above, the MALDI-ToF Mass spectral analysis shows the presence of only those species that are ionizable under the analytical conditions. The intensities of the given peaks are not uniform across the spectrum. In addition, peak positions can vary by ±2 daltons as the instrument, even when calibrated, shows some drift. Furthermore, the peaks that are seen represent components that are present in polymeric versions of the resulting reaction solution give that on concentration the F− catalyst will promote the polymerization of the individual cages.
This invention was made with government support under W911QY-08-C-0098 awarded by the Army Research Laboratory, Natick. The Government may have certain rights in the invention.