POLYMER BOUND CALIXARENES

Abstract: A linear or cross-linked polymer selected from polythioethers, polyethers, styrenic polymers, polyacrylates, and polyorganosiloxanes having a plurality of calixarene groups bound thereon, the calixarene groups having the formula or where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H, hydrocarbyl, -CH₂C(=0)OR³, -CH₂C(=0)R³, or -C(=0)NHR³, R³ is hydro­ carbyl or substituted hydrocarbyl; n is an integer of 1-8, m is an integer of 0.7 and n+m is 4-8.

Description: Background of the invention The ion complexation and enzyme mimic abilities of cyclic phenol -- formalaehyde resins known as calixarenes have recently been reported in such references as Acc. Chem. Res., 16 , 161-170 (1983); Macromol; Chem. Rapid Communications, 3 705-707 (1982); and JACS, 103 3782-3792 (1981). U.S. Patent 4,556,700 describes novel calixarene compounds of the formula; where R¹ is alkyl, alkoxy, substituted alkyl or substi­ tuted alkoxy; R² is H or alkyl; and n=4, 6, or 8, which are particularly useful as storage stable accelerators for cyanoacrylate "instant adhesive" monomer compositions. While a wide variety of calixarene structures and uses are known, heretofore the only suggestion to prepare polymer materials with calixarene moieties attached thereto has been the reaction of diepoxides, polycarboxylic acids or polyamines with calixarene hydroxyl groups, US Pat. 4,259,464. Polymer bound ethers and cryptate compounds, also known for ion complexing abilities, have been reported in such references as US 4256859; 4278784; 4447585; J. Polymer Sci., Polymer Chem. ed., 15 1189-1197 (1977); and Macromolecules, 6 133-142 (1973) Summary of the Invention The invention of this application is novel polymer structures selected from polythioethers, polyethers, styrenic polymers, polyacrylates and polyorganosiloxanes, which include at least one calixarene group bound thereto selected from: where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H hydrocarbyl, _CH₂C(=O)OR³, _CH₂C(=O)R³, or _C(=O)NHR³, R³ is H, hydrocarbyl or a halo or hereto atom substituted hydro­ carbyl group having one or more hydrogen atoms replaced by halo, thio, hydroxy, cyano or amino groups and/or one or more carbon atoms replaced by N, S, O or Si atoms or by carbonyl or sulfonyl groups; n is an integer of 1-8, m is an integer of 0-7 and n+m is 4-8. The calixarene groups terminally or pendently attached to the polymer backbone. The calixarene groups may also be part of a linear or a cross-linked polymeric back­ bone. The polymers are useful as ion exchange resins, phase transfer catalysts, and as coatings, adhesives, or potting materials, especially in electronic applications. A further aspect of the invention are novel dietherified calix (4) arenes from which a wide variety of linear calixarene containing polymers may be prepared. A still further aspect of the invention are novel curable compositions employing functionalized calixarene cross-linked agents. Detailed Description of the Invention Polymer bound calixarene moieties may be incorporated into a wide variety of polymers, including silicones, polyacrylates, polyethers, polyurethanes, polythioethers, and styrene polymers or co-polymers. For instance, calixarenes of the formula: where R⁴ is alkenyl, alkynyl, or (meth) acryl can be polymer bound by hydrosilation or thiol-ene addition reactions using plural SiH or SH functional compounds. Additionally, such calixarenes, especially the (meth) acrylate functional calixarenes may be polymerized free radically using standard peroxide, azo, or photo­ initiators. Still another polymer binding approach is to react parent hydroxy calixarenes or calixarenes having alkyl hydroxy, alkyl thiol or amino functionality, with polyisocyanates in the conventional manner. Still further, compounds or resins with plural alkyl halo functionality may be reacted (a) with calixarene phenolic hydroxyls or their alkaline metal salts to give polyethers, or (b) using Friedel-Crafts chemistry, with calixarenes unsubstituted in the para position to give polymer bound calixarenes linked through p-alkylene groups. Some of these reactions schemes are shown in the following equations: RTV silicone using trialkaxysilylcalixarene cross-linker Alkenyl calixarenes cross-linked with SiH functional silicone Alkenyl calixarenes cross-linked with polythiol to give polythioethers Calixarene (meth) acrylates In addition to reaction with acid halides, (meth) acryl-­ calixarenes may be prepared by reaction of calixarene hydroxyl groups with isocyanato functional (meth) acrylate compounds, such as isocyanotoethyl methacrylate or acrylate, or by the two step reaction with diiso­ cyanates and hydroxy functional (meth) acrylates. Calixarene polyurethanes Calixarenes bound to polymers with reactive halogen (a) etherification of phenolic hydroxyls Calixorenes bound to polymers with reactive halogen (b) Friedel-Crafts reaction Suitable R³ hydrocarbyl groups include methyl, ethyl, phenyl, allyl, propargyl and t-butyl. Examples of suitable halo or hetero atom substituted R³ groups include: Compounds containing such substituted groups may be prepared by conventional organic synthetic methods from the parent phenolic calixarenes or from the corres­ ponding ethyl or allyl acetate calixarene ethers described in the examples by transesterification or by hydrolysis of the ester to the acid, conversion to the acid chloride and then reaction with suitable HOR³, HSR³, or HNR * R³ compounds, where R * is H or the same or different R³ group. The R¹ groups in formulas I and II may be H or any hydrocarbyl group, but most preferably are selected from H and alkyl such as methyl, ethyl and t-butyl. The R¹ groups of formulas I and II may be any hydro­ carbyl group but are most preferably selected from H and alkyl, especially H or t-butyl. The polymer bound calixarenes of the invention are metal ion sequestrants and are, therefore, useful as coatings and encapsulants for ion selective substrates such as electronic circuit boards; as solubilizing agents for ionic materials in polymeric media; and as recoverable phase transfer catalysts. The invention may be illustrated by reference to the following non-limiting examples: Example 1 Preparation of Dietherified Calix (4) arene A mixture of 1.62 g of 5,11,17,23-tetra-tert-butyl calix (4) arene, 2.0 g of ethyl bromoacetate, 2.07 g of anhydrous potassium carbonate, and 20 millilitres of dried DMSO was stirred for 48 hours under nitrogen at room temperature. At the end of this time, the mixture was poured into 200 millilitres of a 10% solution of aqueous hydrochloric acid. The precipi­ tated off-white solid was filtered and washed twice with distilled water to yield 2.0 g of crude product. Re­ crystallization of this material from hot ethanol gave 1.64 g of a crystalline product (m.pt.=173-175°C) which was characterized by i.r. and n.m.r. spectroscopy as the dietherified calix (4) arene: Elemental analysis: (Calc′d for C 52 H 68 O₈ C: 76.04, H: 8.36 O: 15.59; Found, C: 75.59, H: 8,31, O: 16.03). Example 2 A mixture of 1.65 g of dietherified calix (4) arene prepared as in Example 1, 0.096 g of sodium hydride, and 25 millilitres of dry THF was refluxed for 21 hours under nitrogen and then 0.585 g of allyl bromide was added dropwise over 10 minutes. The entire mixture was then refluxed for a further one hour, cooled and poured into 150 millilitres of a 10% solution of aqueous hydrochloric acid. The precipitated off-white solid was filtered and dried at 50°C overnight. Recrys­ tallization of this material from hot ethanol gave 1.5 g of a crystalline product (M.Pt.=167-168°C) which was characterized by i.r. and n.m.r. spectroscopy as a diallyl calix (4) arene: Elemental analysis: (Calc′d for C 58 H 76 O₈ C: 77.28, H: 8.52, O: 14.20; Found, C: 76.87, H: 8.35, O: 13.82). Example 3 Preparation of Calix (4) arene Diallylacetate Ester A mixture of 1.9 g of dietherified calix (4) arene prepared as in Example 1. 1.04 g of allyl bromoacetate, and 1.0 g anhydrous potassium carbonate was heated to 130°C under nitrogen with stirring for 30 min. The resulting solid mass was cooled and added to 100 millilitres of a 10% solution of aqueous hydrochloric acid. The undissolved solid was filtered, washed twice with distilled water and dried overnight at 55°C to give 2.7 g of crude product. Recrystallization of this material from hot ethanol yielded 2.1 g of a crystalline product (M.Pt.=115°C) which was characterized by i.r. and n.m.r. spectroscopy as a diallyl ester of calix (4) arene. Elemental analysis: (Cald′d for C 62 H 80 O 12 C: 73.18, H: 7.94, O: 18.87; Found C: 73.24, H: 8.14, O: 19.08). Example 4 Preparation of Polyurethane-Bound Calixarene A mixture of 0.339 g of dietherified calix (4) arene prepared as in Example 1, 0.144 g toluene diisocyanate, one drop of stannous octoate, and 5 milliliters of dried chlorobenzene was heated for 48 hours at 65°C under nitrogen. To this mixture was added 0.83 g of poly(ethylene glycol) of molecular weight 2000 and the entire mixture was then heated for 24 hours at 65°C. After this time, infrared spectroscopic analysis indicated complete comsumption of the isocyanate. The product was then precipitated with petroleum ether and characterized by i.r. spectroscopy and gel permeation chromatography as a polyurethane containing calixarene subunits. Example 5 Preparation of Silicone-Bound Calixarene A mixture of 0.250 g of the diallyl calix (4) arene prepared as in Example 2, and 16 milliliters of dry toluene containing 50 parts per million of platinum (as dihydrogen hexachloroplatinate hexahydrate) was heated to 78°C under nitrogen. To this mixture was added a solution of 0.277 g of a difunctional Si-H terminated polydimethysiloxane resin of molecular weight 1010 in one milliliter of toluene gradually over 5 minutes. After a further 20 minutes at 78°C, volatiles were removed on a rotary evaporator yielding 0.484 g of a viscous, colorless oil, soluble in common organic solvents, which was characterized by infrared and n.m.r. spectroscopy and liquid chromatography as a low-molecular weight silicone polymer (mw ca 1950) containing calixarene subunits. Example 6 Preparation of Silicone-Bound Calixarene A mixture of 0.305 g of the diallyl ester of calix (4) arene as prepared in Example 3, and 20 milliliters of dry toluene containing 50 parts per million of platinum (as dihydrogen hexaloroplatinate hexahydrate) was heated to 78°C under nitrogen. To this mixture was added a solution of 0.303 g of a difunctional Si-H terminated polydimethylsiloxane resin of molecular weight 1010 in one milliliter of toluene gradually over 5 minutes. After a further 20 minutes at 78°C, volatiles were removed on a rotary evaporator yielding 0.63 g of a viscous, pale grey oil, solidifying on standing to a waxy solid which was soluble in common solvents and which was characterized by infrared and n.m.r. spectroscopy and liquid chromatography as a low-molecular weight silicone polymer (mw ca 2000) containing calixarene subunits. Example 7 Preparation of Calixarene-Containing Polyurethane Gel To 0.212 g of unsubstituted calix (6) arene: in 5 milliliters of dry dichloromethane was added 0.348 g of toluene diisocyanate and one drop of Stannous octoate catalyst. This mixture was stirred for 24 hours under nitrogen at room temperature. After that time, infrared spectrophotometric analysis showed diminution of the band at 2260 cm _1 attri­ butable to the isocyanate group and the appearance of a new band at 1720 cm _1 attributable to a carbamate carbonyl group. To the mixture was then added 2.0 g of poly(ethylene glycol) of molecular weight 2000 and the resulting mixture was stirred under nitrogen for 17 hours at room temperature to give a very viscous solution. Infrared analysis of this product showed no absorbance at 2260 cm _1 indicating complete comsumption of the isocyanate. The viscous solution gelled on further standing. By use of chlorobenzene in place of dichloromethane and gradual removal of solvent in a mold it was possible to cast clear, colorless, brittle films of the material. The dried film was insoluble in common organic solvents, indicating substantial cross-linking. Example 8 Preparation of 5, 11, 17, 23-Tetra-Allyl Calix (4) arene Ester A mixture of 1.28 grams of unsubstituted calix (4) arene, 0.58 grams sodium hydride, and 25 milliliters of dry THF was refluxed for one hour under nitrogen. After this time, 2.92 grams of allyl bromide was added dropwise over 10 minutes. The entire mixture was then refluxed overnight. After cooling, the reaction mixture was treated with three milliliters of water, dried on a rotary evaporator under vacuum, dissolved under vacuum, dissolved in ether and extracted with an equal volume of water. The ether layer was then dried over magnesium sulfate and solvent was removed under vacuum to yield 1.38 grams of a off-white powder characterized by infrared spectroscopy as 25, 26, 27, 28-tetra-allyloxy calix (4) arene. This material was dissolved in 17 milliliters of dimethyl-p-toluidine and heated with stirring to 220°C for 4 hours under nitrogen. The cooled solution was treated with dilute aqueous sulfuric acid precipi­ tating a white solid which was washed with water and dried to yield 1.4 grams of a material characterized by infrared spectroscopy as 5, 11, 17, 23-tetra-allyl calix (4) arene. To this material (0.858 grams) was added 1.96 grams of ethyl bromoacetate, 1.22 grams potassium carbonate, and 20 milliliters of acetone. The entire mixture was refluxed under nitrogen for 5 days, poured into dilute aqeous sulfuric acid, extracted into dichloromethane, dried over magnesium sulfate and solvents were removed to yield 1.32 grams of a pale yellow oil characterized by infrared spectroscopy and liquid chromatography as 5, 11, 17, 23-tetra-allyl 25, 26, 27, 28-tetra-(2-ethoxy-2-oxo-) ethoxy calix (4) arene. Example 9 Preparation of Silicone-Bound Calixarene A mixture of 0.149 grams of the tetra-allyl calixarene ester prepared in Example 8, and 10 milliliters of dry toluene containing 50 parts per million of platinum (as dihydrogen hexachloroplatinate hexahydrate) was heated to 80°C under nitrogen. To this mixture was added a solution of 0.324 grams of a difunctional Si-H terminated polydimethylsiloxane resin of molecular weight 1010 in one milliliter of toluene over 5 minutes. After a further 20 minutes at 80°C, volatiles were removed on a rotary evaporator yeilding 0.472 grams of a viscous pale yellow oil which was characterized by infrared spectroscopy and viscometry as a high polymer containing silicone and calixarene subunits. Example 10 Preparation of Calixarene-Containing Polystyrene Gel A swollen cross-linked chloromethylated polystyrene matrix was prepared by treating 0.320 grams of a Merrifield polymer (200-400 mesh, 2% divinylbenzene, 5 mmol Cl/g) with dichloromethane for 15 minutes, filtering and drying. The swollen polymer was then stirred together with 10 milliliters of dry nitromethane, 0.307 grams of 37, 38, 39, 40, 41, 42-hexa-(2-ethoxy-2-oxo) ethoxy calix (6) arene, and 0.214 grams of powdered anhydrous aluminum chloride at 100°C for 10 minutes under nitrogen. The mixture was then maintained at 40°C for 17 hours, poured into methanol, washed with a hot methanol/aqeous hydrochloric acid solution, with water, with methanol, and finally extracted with acetone for 5 hours to yield 0.221 grams of material charac­ terized by infrared spectroscopy as a polystyrene gel containing bound calixarene units. Example 11 Preparation of Calixarene-Containing Polystyrene Gel A swollen cross-linked chloromethylated polystyrene matrix was prepared as described in Example 10, and added to a mixture of 5 milliliters of dry THF, and 0.300 grams of the dietherified calix (4) arene described in Example 1 which had been pre-reacted with 0.019 grams of sodium hydride. This mixture was heated to reflux under nitrogen for 4 hours, then poured into methanol. The resulting yellow solid was washed and extracted as described in Example 10 to yield 0.263 grams of a pale yellow material which was characterized by infrared spectroscopy as a polystyrene gel containing bound calixarene units. Example 12 Ion-Extraction by Polymer-Bound Calixarenes The ion binding abilities of polymer-bound calixarenes were measured by extraction of metal picrates from aqeous into organic media. In each experiment a solution of the calixarene-containing polymer in dichloromethane was prepared such that the concentration of calixarene subunits was 2.5 × 10 _4 M. A solution of picric acid in 0.1M aqeous sodium hydroxide was prepared such that the concention of sodium picrate was 2.5 × 10 _4 M. Equal volumes of each solution (5 milliliters) were shaken together for 3 minutes and the percentage extraction of sodium picrate into the organic phase was determined by measuring the increase in absorbance of the dichloromethane layer at 387 mm in a spectrophotometer. The results are presented in Table 1. Example 13 Calixarene Polythioether A formulation was prepared consisting of 1.0004 g of 5, 11, 17, 23, 29, 35-hexa-t-butyl-37, 38, 39, 40, 41, 42-hexa allyloxy calix (6) arene, 0.6032 g of pentaerythritol tetrakis (β-mercapto-propionate), 0.0351 g of 2,2-dimethoxy-2-phenyl acetophenone, 8.94 g of toluene, and 9.56 g of chloroform. This solution was coated onto a silicone-treated polyester film and irradiated under a medium-pressure Mercury arc at an intensity of 55 mw/cm² at 365 nm for 15 seconds followed by a post­ bake at 90°C for one hour to remove residual solvents. The formulation had cured to a brittle film. Example 14 Preparation and Copolymerization of Acrylated Calix (6) arene To a mixture of 0.212 g of unsubstituted calix (6) arene in 10 milliliters of 2-methoxyethyl ether at 0°C was added 0.336 g of potassium hydroxide dissolved in one milliliter of water. The resultant mixture was stirred while 0.546 g of acryloyl chloride was added dropwise over 10 minutes. The reaction mixture was then warmed to room temperature while being stirred for a further 45 minutes. Filtration, washing three times with distilled water, and drying yielded 0.33 g of an off-white powder. Chromatography on an acid-­ washed alumine column using dichloromethane as eluent gave a colourless powdered product which was characterized by infrared and n.m.r. spectroscopy as the pentaacrylate of calix (6) arene. A solution was prepared consisting of 0.050 g of this acrylated calixarene, 1.0 g of tetrahydrofuryl acrylate, and 0.01 g of 2,2-dimethoxy-2-phenyl acetophenone. The solution was irradiated for 90 seconds under a medium-­ pressure mercury arc to yield a solid copolymer. Example 15 A formulation was prepared consisting of 0.1 gram of the acrylated calix (6) arene synthesized in Example 14, 1.0 gram of 2-phenylethyl methacrylate and 0.01 gram of 2,2-dimethoxy-2-phenyl acetophenone. A 2 mm thick film of this formulation in a mold was irradiated under a medium-pressure mercury arc for 180 seconds. At the end of this time, the formulation had hardened to a material insoluble in common organic solvents. A similar formulation but without the acrylated calix (6) arene, when irradiated under identical conditions, yielded only readily soluble material. Example 16 Alkoxysilane Calixarene Cross-Linked RTV Silicone A mixture of 0.252 g of the product of Example 8 (0.00027 mole) and 10 mls dry toluene containing 50 ppm of platinum (as dihydrogen hexachloroplatinate hexahydrate) was heated to 80°C under nitrogen. To this was added a solution of 0.178 g (0.00108 mole) triethoxysilane in 1 ml dry toluene (containing an identical level of platinum) during 10 minutes. After 30 minutes at 80°C there was no indication of any reaction having taken place i.e. no reduction in peak in infra red spectrum at 1630 cm _1 of C=C. The mixture was then taken to 120°C (and left there for 96 hr.) and after this time reaction was adjudged to be complete, no absorption at 1630 cm _1 , and volatiles were removed under reduced pressure to give 0.465 g ca 100% of a triethoxysilyl calix (4) arene of the formula: which was mixed with 4.65 g of polydimethylsiloxanediol of 50,000 cps viscosity and 0.046 g of stannous octanoate catalyst. The triethoxysilyl calixarene acted as a cross-linker, and in several hours a solid cured slug of clear colourless RTV silicone was produced. The vulcanized RTV silicone was insoluble in common solvents.

Claims: 1. A linear or cross-linked polymer selected from polythioethers, polyethers, styrenic polymers, polyacrylates, and polyorganosiloxanes having a plurality of calixarene groups bound thereon, the calixarene groups having the formula where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H, hydrocarbyl, _CH₂C(=0)OR³, _CH₂C(=0)R³, or _C(=0)NHR³, R³ is hydrocarbyl or substituted hydrocarbyl; n is an integer of 1-8, m is an integer of 0-7 and n+m is 4-8. 2. A. polymer as in Claim 1 comprising the addition reaction product of a compound having at least two thiol groups per molecule and a calixarene compound as in formulas III or IV: where R⁴ is an ethylenically or acetylenically usaturated group. 3. A Polymer as in Claim 1 comprising the hydro­ silation reaction product of a compound having at least two silicon hydride groups per molecule and a calixarene compound as in formulas III or IV; where R⁴ is an ethylenically or acetylenically unsaturated group. 4. A polymer as in Claim 1 comprising the reaction product of a compound having at least two isocyanate groups per molecule and a calixarene compound as in formula V: 5. A polymer as in Claim 1 wherein at least one of said R² is _C(=0)-NH-C₂H₄-O-C(=0)-C(CH₃)=CH₂. 6. A polymer as in Claim 1 wherein at least two said R₂ groups are _CH₂C(=0)-OC₂H₅. 7. A polymer as in Claim 1 wherein the calixarene group has the formula I, R² is CH₂C(=0)OR³; and n and m are both equal to 2. 8. A polymer as in Claim 1 further comprising a plurality of diorganosiloxane repeat units. 9. A polymer as in Claim 1 wherein the polymer comprises a styrene copolymer at least some of which styrenic benzene groups include a p-methylene group to which said calixarene moiety is bound. 10. A calixarene compound of the formula: where R¹ is H or hydrocarbyl, R³ is hydrocarbyl or substituted hydrocarbyl and R⁴ is H or an ethyl­ enically or acetylenically unsaturated group. 11. A compound as in Claim 10 where R¹ and R³ are alkyl. 12. A compound as in Claim 11 where R⁴ is H. 13. A compound as in Claim 11 where R⁴ is selected from allyl and _CH₂C(=0)OCH₂CH=CH₂. 14. A calixarene compound of the formula: where R² is H, hydrocarbyl, CH₂C(=0)OR³, CH₂C (=0)R³ or C(=0)NHR³; R³ is hydrocarbyl or substituted hydrocarbyl; R⁵ is alkylene or )alkenylene; R⁶ is alkyl or aryl; and k is 4-8. 15. A calixarene compound of the formula: where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H, hydrocarbyl, _CH₂(=0)OR³ or _CH₂C(=0)R³;R³ is hydrocarbyl or substituted hydrocarbyl, R⁷ is an acrylate or methacrylate functional group, n is an integer of 1-8, m is an integer or 1-8, m is an integer or 0-7 and n+m is 4-8. 16. A compound as in Claim 15 where R⁷ is selected from C(=0)CH=CH₂ and C(=0)C(CH₃)=CH₂. 17. A compound as in Claim 15 where R⁷ is C(=0)NHC₂H₄O(0=)CCH=CH₂ or C(=0)NHC₂H₄O(0=)CC(CH₃)=CH₂. 18. A composition curable to a cross-linked polymer comprising a compound as in Claim 14, a SiOH functional polyorganosiloxane compound; and a condensation catalyt. 19. A composition curable to a cross-linked polymer comprising a compound as in Claim 15 and a free radical initiator. 20. A composition curable to a cross-linked polymer comprising a calixarene compound of the formula: where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H, hydrocarbyl, _CH₂C(=0)OR³, _CH₂C(=0)R³ or C(=0)NHR³; R³ is hydrocarbyl or substituted hydrocarbyl; R⁴ is an ethylenically or acetylenically unsaturated group and n is an integer of 2-8, m is an integer of 0-6 and n+m is 4-8; a polythiol and a free radical initiator. 21. A composition curable to a cross-linked polymer comprising (a) a calixarene compound of the formula: where the R¹ groups are the same or different H or hydrocarbyl groups; the R² groups are H, hydrocarbyl, _CH₂C(=0)OR³ _CH₂C(=0)R³ or C(=0)NHR³; R³ is hydrocarbyl or substituted hydrocarbyl R⁴ is an ethylenically or acetylenically unsaturated group and n is an integer of 2-8, m is an integer of 0-6, and n+m is 4-8; (b) a polyorganosiloxane having a plurality of SiH groups; and (c) a hydrosilation catalyst.

Inventors: HARRIS, STEPHEN J., ROONEY, JOHN M., WOODS, JOHN G.
Applicants: LOCTITE (IRELAND) LTD.
Application year: 1986
Main classification: C08G85
IPC codes: C07F7, C08G85, C08G18, C08F8, C08G77