Patent Application
20120226000
The present invention concerns multiarmed star copolymers containing polyvinyl chloride moieties.
The industrial scale synthesis of PVC involves conventional free-radical polymerization. This polymerization method is accompanied by secondary inter- and intramolecular chain transfer reactions, which lead to the formation of PVC with structural defects, such as tertiary chlorine, internal and terminal chloroallylic groups, and other irregularities such as chloromethyl and chloroethyl branches. See, Starnes, et al., J Polym Sci Part A: Polym Chem 2005, 43, 2451-2467; Asandei and Percec, J Polym Sci Part A: Polym Chem 2001, 39, 3392-3418; and Purmova, et al., Macromolecules 2005, 38, 6352-6366. The presence of these structural defects reduces the thermal stability of PVC and limits its technological applications.
Living polymerizations provide access to polymers of predetermined molecular weight, functional chain ends and narrow molecular weight distribution. Various approaches to living radical polymerization (LRP) have been elaborated for the synthesis of functional polymers with linear and more complex topologies. See, Otsu, Polym Sci Part A: Polym Chem 2000, 38, 2121-2136; Solomon, J Polym Sci Part A: Polym Chem 2005, 43, 5748-5764; Hawker, et al., Chem Rev 2001, 101, 3661-3688; Perrier and Takolpuckdee, Polym Sci Part A: Polym Chem. 2005, 43, 5347-5393; Barner-Kowollik and Perrier, J Polym Sci Part A: Polym Chem. 2008, 46, 5715-5723; Yamago, J Polym Sci Part A: Polym Chem 2006, 44, 1-12; Kamigaito and Satoh, J Polym Sci Part A: Polym Chem 2006, 44, 6147-6158; Kamigaito, et al, M. Chem Rev 2001, 101, 3689-3746; Braunecker and Matyjaszewski, Prog Polym Sci 2007, 32, 93-146; Percec, et al. J Am Chem Soc 2003, 125, 6503-6516; Percec, et al., J Polym Sci Part A: Polym Chem 2004, 42, 505-513; and Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 4894-4906. Until several years ago LRP methods were available only for activated monomers such as acrylates, methacrylates, acrylonitrile, styrene, etc. It was considered that VC would not be accessible by any living polymerization mechanism including LRP. See, Stockland, and Jordan, J Am Chem Soc 2000, 122, 6315-6316; Stockland, et al., J Am Chem Soc 2003, 125, 796-809; Foley, et al., J Am Chem Soc 2003, 125, 4350-4361; Queffelec, et al., Macromolecules, 2000, 33, 8629-8639. Recently, our laboratory discovered two closely related LRP methods which are compatible with vinyl chloride, namely Single Electron Transfer-Degenerative Chain Transfer Living Radical Polymerization (SET-DTLRP) and Single Electron Transfer-Living Radical Polymerization (SET-LRP). See, Percec, et al., J Am Chem Soc 2002, 124, 4940-4941; Percec, et al., J Polym Sci Part A: Polym Chem 2003, 41, 3283-3299; Percec, et al., J Polym Sci Part A: Polym Chem 2004, 42, 6267-6282; Percec, et al., J Polym Sci Part A: Polym Chem 2004, 42, 6364-6374; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 287-295; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 773-778; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 779-788; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 2185-2187; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 2276-2280; Coelho, et al., J Polym Sci Part A: Polym Chem 2006, 44, 3001-3008; Coelho, J et al., Mat Sci Forum 2006, 514-516, 975-979; Coelho, et al., Eur Polym J2006, 42, 2313-2319; Coelho, et al., J Vinyl Addit Technol 2006, 12, 156-165; Coelho, et al., J Appl Polym Sci 2008, 109, 2729-2736; Percec, et al., PCT Int Appl 2002 WO 0277043; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 1478-1486; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 1649-1659; Percec, et al., J Polym Sci Part A: Polym Chem 2005, 43, 1660-1669; Percec, et al., J Polym Sci Part A: Polym 29 Chem 2005, 43, 1948-1954; Coelho, et al., J Polym Sci Part A: Polym Chem 2006, 44, 2809-2825; Coelho, et al., Macromol Chem Phys 2007, 208, 1218-1227; Coelho, et al., J Polym Sci Part A: Polym Chem 2008, 46, 421-432; Coelho, J et al., J Polym Sci Part A: Polym Chem 2008, 46, 6542-6551; Percec, et al., J Am Chem Soc 2006, 128, 14156-14165; Guliashvili, T.; Percec, Polym Sci Part A: Polym Chem 2007, 45, 1607-1618; Monteiro, et al., J Polym Sci Part A: Polym Chem 2007, 45, 1835-1847; Lligadas and Percec, J Polym Sci Part A: Polym Chem 2007, 45, 4684-4695; Rosen, J Polym Sci Part A: Polym Chem 2007, 45, 4950-4964; Lligadas, et al., J Polym Sci Part A: Polym Chem 2008, 46, 278-288; Lligadas and Percec, J Polym Sci Part A: Polym Chem 2008, 46, 2745-2754; Lligadas and Percec, J Polym Sci Part A: Polym Chem 2008, 46, 3174-3181; Lligadas and Percec, V. J Polym Sci Part A: Polym Chem 2008, 46, 4917-4926; Lligadas and Percec, J Polym Sci Part A: Polym Chem 2008, 46, 6880-6895; and Rosen and Percec, J Polym Sci Part A: Polym Chem 2008, 46, 5663-5697.
SET-DTLRP is initiated with iodoform or other iodo-containing initiators including methylene iodide and catalyzed by Cu(0), Cu2O, Cu2S, Cu2Se, Cu2Te, CuCl, CuI in the presence of a ligand and solvent that mediates the disproportionation of Cu(I)X by Na2S2O4 and (NH2)2C═SO2 in water at ambient temperature. S2O42− dissociates in organic phase (VC) into the radical anion SO2−•which acts as an electron-donor that mediates the activation step of dormant propagating species via a SET mechanism. Both SET-LRP and SET-DTLRP processes proceed via a single-electron transfer (SET) mechanism at least in the activation step. When VC is polymerized with Na2S2O4, degenerative transfer (DT) is the dominant pathway for reversible deactivation.
In some aspects, the invention concerns processes for the production of multiarmed star copolymers comprising polymerizing vinyl chloride with a multifunctional initiator in the presence of Na2S2O4 and water. Certain multifunctional initiator are bifunctional or tetrafunctional initiators. In certain embodiments, the multifunctional initiators are iodo terminated. Certain of these initiators contain 2 or 4 terminal groups of formula I or formula II:
where R is a C1-C4 alkyl group or a C1-C4 alkoxy group. In some embodiments, R is methyl. Preferred multifunctional initiators include 1,2-bis(iodopropionyloxy)ethane, dimethyl 2,5-diiodohexanedioate, bis(2-methoxyethyl)-2,5-diiodohexanedioate, pentaerythritol tetrakis(2-iodopropionate), or [PBA-CH(CH3)—COO—CH2]4C where PBA is iodo terminated poly(n-butyl acrylate).
In certain embodiments, the terminal groups of formula I or II are attached to an alkyl, aryl, arylalkyl or alkylaryl core group.
In some embodiments, the molar ratio of Na2S2O4 to multifunctional initiator is 2:1 to 100:1. In certain embodiments, the molar ratio of vinyl chloride to multifunctional initiator is 500 to 10,000. Some contacting/reacting steps are performed at a temperature of 20 to 60° C. In certain embodiments, the molar ratio of Na2S2O4 to multifunctional initiator is 2:1 to 100:1, the molar ratio of vinyl chloride to multifunctional initiator is 500 to 10,000, and the contacting is performed at a temperature of 20 to 60° C.
Some polymer produced by the instant processes have each arm of the multiarmed star copolymer has a molecular weight (Mn) of 200 to 35,000.
In some embodiments, a chain of poly(n-butyl acrylate) can be attached at the iodo-substituted position of formula I or II. An iodo terminated poly(n-butyl acrylate) chain can be added, for example, via SET-DTLRP of n-butyl acrylate via techniques described herein.
In certain processes, the multiarmed star copolymer comprises [PVC-b-PBA-CH(CH3)—COO—CH2]4C where PVC is polyvinyl chloride and PBA is poly(n-butyl acrylate). In this construction, PVC is attached to the PBA section of the arm at the terminal end of the arm.
The invention also concerns the intermediate compound [PBA-CH(CH3)—COO—CH2]4C where PBA is iodo terminated poly(n-butyl acrylate).
The invention also concerns articles made from the compounds described herein. Certain preferred articles are substantially free of plasticizer. By substantially free of plasticizer is meant that the article contains less than 5% or 1% or 0.1% by weight of plasticizer. In some embodiments, the articles is substantially free of phthalates. As used herein “phthalates” means esters of phthalic acid. Some esters are C1-C15 esters. Other esters are C4-C15.
The invention also concerns multiarmed star copolymers comprising polyvinyl chloride polymer described herein. In another aspect the invention concerns processes for making an article comprising polyvinyl chloride comprising forming said article from a multiarmed star copolymer comprising polyvinyl chloride made by the process described herein, the performing occurring substantially in the absence of a plasticizer.
In one aspect, the invention concerns Na2S2O4 catalyzed Single-Electron Transfer-Degenerative Chain Transfer mediated Living Radical Polymerization (SET-DTLRP) of vinyl chloride (VC) initiated with multifunctional initiators such as bifunctional initiators 1,2-bis(iodopropionyloxy)ethane, dimethyl 2,5-diiodohexanedioate, and bis(2-methoxyethyl)-2,5-diiodohexanedioate as well as the tetrafunctional initiator pentaerythritol tetrakis(2-iodopropionate). This SET-DTLRP can be performed in water at ambient temperature in the presence of polyvinyl alcohol and hydroxypropyl methylcellulose surfactants. The invention provides methods for the synthesis of α,ω-di(iodo)PVC with two identical active chain ends and of the four-arm star PVC with four identical active chain ends. These difunctional and tetrafunctional derivatives of PVC are also macroinitiators for the synthesis of ABA triblock copolymers and four-arm star block copolymers.
In some embodiments, the synthesis by SET-DTLRP is catalyzed by Na2S2O4 in water in the presence of Celvol 540 and Methocel K100 of perfectly bifunctional and four-arm star tetrafunctional iodo-terminated PVC. The synthesis of bifunctional and tetrafunctional initiators employed in this process is also detailed herein.
The present invention also teaches use of a tetrafunctional initiator for the synthesis of the first example of four-arm star-block copolymer containing PVC and poly(n-butyl acrylate) (PBA) segments. This novel PVC based topology [PVC-b-PBA-CH(CH3)—CO—O—CH2]4C was accessed by the SET-DTLRP catalyzed by Na2S2O4 in water at ambient temperature initiated from a tetrafunctional initiator.
The PVC containing star block copolymer produced herein have industrial potential over flexible and structural PVCs currently based on 1) improved or new properties, 2) lower cost, and/or 3) reduction in the use of toxic or environmentally problematic plasticizers currently added to achieve flexibility. Currently these flexible PVCs may contain as much as 60% by weight of plasticizers.
One class of toxic plasticizer that has received attention is the phthalates. The Washington [State] Toxics Coalition reports that phthalates can be found in PVC wallpaper, flooring, shower curtains, raincoats, packaging, medical equipment and tubing, and toys. Phthalates are not chemically bound to PVC and therefore can leach out of products over time, and can be found in air inside buildings and in dust. Phthalates have been found in groundwater, surface water, and sediment. Phthalate syndrome can potentially lead to abnormal development of the male reproductive system because they are endocrine disruptors that either mimic or block the action of human hormones. The Washington Toxics Coalition has been particularly concerned with children's toys where up to 47% phthalates were found in common toys such as rubber ducks. Phthalates in toys and children's products have been banned by the European Union, but are allowed in most of the US except for California. A PVC block copolymer achieving flexibility without toxic plasticizers, has potential to revolutionize the manufacturing process.
Another potential advantage to the instant technology is PVC could be used in thermoplastic elastomers (TPEs) with a potential to reduce raw material costs. Most polymer costs directly relate to the cost of petroleum; however, because PVC is half composed of inexpensive chloride reacted from salt, only half of its raw material cost tracks with petroleum.
Potential applications of the star polymers disclosed herein include resin compounds; lubricants; colloidal stabilizers; binders; and pressure sensitive adhesives. The star structure, as opposed to a linear structure, has the ability to modify rheology, viscosity, and durability of copolymers formed. Biocompatible star copolymers also have potential as micelles for drug delivery.
As used herein, the term “alkyl”, whether used alone or as part of another group, refers to a substituted or unsubstituted aliphatic hydrocarbon chain and includes, but is not limited to, straight and branched chains containing from 1 to 12 carbon atoms. Examples of alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, i-butyl and t-butyl. Specifically included within the definition of “alkyl” are those aliphatic hydrocarbon chains that are optionally substituted.
The term “aryl”, as used herein, means an optionally substituted aromatic 5- to 13-membered mono- or bi-carbocyclic ring such as phenyl, naphthyl, or biphenyl. Preferably, groups containing aryl moieties are monocyclic having 5 to 7 carbon atoms in the ring. Phenyl is one preferred aryl.
The term “arylalkyl”, as used herein, refers to the group —Rc-Rd, where Rc is an alkyl group as defined above, substituted by Rd aryl group(s), as defined above.
The term “alkylaryl”, as used herein, refers to the group —Re-Rf, where Re is an aryl group as defined above, substituted by Rf alkyl group(s), as defined above.
The carbon number as used in the definitions herein refers to carbon backbone and carbon branching, but does not include carbon atoms of the substituents.
Optional substituents on the aforementioned groups include, for example, nitro, cyano, —N(Ra)(Rb), halo, hydroxy, carboxy, alkyl, alkenyl, alkynyl, cycloalkyl, aryl, heteroaryl, alkoxy, aryloxy, heteroaryloxy, alkylalkoxy, alkoxycarbonyl, alkoxyalkoxy, perfluoroalkyl, perfluoroalkoxy, arylalkyl, alkylaryl, hydroxyalkyl, alkoxyalkyl, alkylthio, —S(O)2—N(Ra)(Rb), —C(═O)—N(Ra)(Rb), (Ra)(Rb)N-alkyl, (Ra)(Rb)N-alkoxyalkyl, (Ra)(Rb)N-alkylaryloxyalkyl, —S(O)s— aryl (where s=0-2) or —S(O)s-heteroaryl (where s=0-2). Ra and Rb are optionally substituted alkyl or aryl.
The invention is illustrated by the following examples which are intended to be illustrative and not limiting.
Vinyl chloride (VC, 99%) was purchased from Aldrich. Sodium dithionite (85%) was purchased from Lancaster and stored under N2. The sodium salt of p-toluenesulfinic acid, hydrate (98+%) was purchased from Acros Organics. 2-Bromopropionyl bromide (97%, Aldrich), ethylene glycol (99+%, Acros), pentaerythritol (98%, Aldrich), pyridine (99.9%, Fisher), thionyl chloride (99.5%, Sigma), bromine (Acros Organics), adipic acid (98%, Acros Organics), sodium iodide (Fisher), methanol (Fisher), 2-methoxyethanol (99+%, Acros Organics), acetone (Fisher) were used as received. Celvol 540 and Methocel K100 were provided by COLORITE. Anhydrous THF (Fisher) was obtained by distillation from sodium benzophenone ketyl under an inert atmosphere of nitrogen.
1H 500 MHz NMR and HMQC spectra were recorded on Brucker DRX500 NMR and Brucker DMX600, respectively at 20° C. in CD2Cl2 (PVC). Gel Permeation Chromatographic (GPC) analysis of PVC samples was performed on Perkin-Elmer Series 10 high performance liquid chromatograph, equipped with LC-100 column oven (40 and 25° C.), Nelson Analytical 900 Series integration data station, Perkin-Elmer 785A UV-Vis detector (254 nm), Varian star 4090 refractive index (RI) detector, and two AM gel (500 Å, 5 μm and 104 Å, 5 μm for low molecular weight samples) columns. THF (Fisher) was used as an eluent at a flow rate of 1 mL/min. The number average molecular weight (Mn) and the weight average molecular weight (Mw) of PVC samples were determined with PS standards purchased from Pressure Chemical and were corrected with the Universal Calibration (Hutchinson, et al., DECHEMA Monogr 1995, 131, 467-492 using Mark-Houwink parameters for PVC: K=1.50×10−2 mL/g, a=0.77 (Kurata and Tsunashima, In Polymer Handbook; Brandrup, et al., Eds.; Wiley: New York, 1999, p 1-83).
To a 0° C. cooled solution of ethylene glycol (0.047 mol, 2.92 g, 2.62 mL) and pyridine (0.097 mol, 7.67 g, 7.84 mL) in dry THF (30 mL), a solution of 2-bromopropionyl bromide (0.97 mol, 21.02 g, 10.20 mL) in dry THF (10 mL) was added drop-wise under N2 over a period of 1.5 h. The reaction was allowed to warm up to room temperature overnight. The precipitated salt was filtered off and the solvent was evaporated. The crude product was dissolved in CH2Cl2 and the solution was washed with aqueous solution of NaHCO3, brine and water. The organic layer was separated and dried with Na2SO4. The solvent was evaporated and the crude BBPE was purified by column chromatography (silica gel) with hexane/ethyl acetate (9/1) as eluent to yield 11.71 g of colorless oil. Yield: 75%. 1H NMR (500 MHz, CDCl3, ppm): δ 1.84 (overlapped d, J=6.9 Hz, 6H, 2CH3), 4.38-4.46 (m, 6H, 2CH2 and 4CH). 13C NMR (125 MHz, CDCl3, ppm): 21.68 (2CH3), 39.74-39.75 (2CH), 63.18 (2CH2), 170.08 (2C═O).
To a solution of NaI (0.462 mol, 69.25 g) in acetone (150 mL) at 25° C., a solution of bis(2 bromopropionyloxy) ethane (BBPE, 0.077 mol, 25.57 g) in acetone (50 mL) was added rapidly. The precipitation of NaBr appeared after approximately 10-20 s. The reaction mixture was stirred until complete disappearance of BBPE on 1H NMR spectrum. The reaction was complete in 2 h. NaBr was filtered off, the reaction mixture was diluted with water and the product was extracted into CH2Cl2. The organic solution was washed with 2% aqueous solution Na2SO3 followed by brine and water. The organic layer was separated and dried with Na2SO4. The solvent was evaporated and the crude product was purified on silica gel plug with hexane/ethyl acetate (9/1) as eluent to yield 25.57 g of colorless oil which darkened quickly to orange. Yield: 78%. 1H NMR (500 MHz, CDCl3, ppm): δ 1.98 (overlapped d, J=7.0 Hz, 6H, 2CH3), 4.38 (unresolved t, J=1.01 Hz, 4H, CH2CH2), 4.51 (overlapped quartet, J=7.0 Hz, 2H, 2CH). 13C NMR (125 MHz, CDCl, 3, ppm): 12.51-12.54 (2 CH3), 23.40 (2 CH), 63.00 (2CH2), 171.76 (2C═O).
To a 0° C. cooled solution of pentaerythritol (0.075 mol, 10.21 g) and pyridine (0.303 mol, 24.96 g, 24.5 mL) in dry THF (220 mL), a solution of 2-bromopropionyl bromide (0.303 mol, 65.4 g, 32.06 mL) in dry THF (30 mL) was added drop-wise in the atmosphere of N2 over a period of 2 h. The reaction was allowed to warm up to room temperature overnight. The precipitated salt was filtered and the solvent was evaporated. The crude product was recrystallized from EtOH to yield 37.78 g of white solid. Yield: 75%. 1H NMR (500 MHz, CDCl3, ppm): δ 1.83 (d, J=6.9 Hz, 12H, 4CH3), 4.21-4.38 (m, 8H, 4CH2), 4.40 (quartet, J=6.9 Hz, 4H, 4CH). 13C NMR (125 MHz, CDCl3, ppm): 21.65 (4CH3), 39.51-39.58 (4CH), 43.40-44.43.42 (C(CH2)4), 63.18-63.21 (4CH2), 169.63-169.66 (4C═O).
To a solution of NaI (0.09 mol, 13.50 g) in acetone (150 mL) at 25° C., a solution of pentaerytritol tetrakis(2-bromopropionate) (4BrPr, 0.015 mol, 10.14 g) in acetone (100 mL) was added rapidly. The precipitation of NaBr appeared after approximately 10-20 s. The reaction mixture was stirred until complete disappearance of 4BrPr on 1H NMR. The reaction was complete in 6 h. NaBr was filtered off, the solvent was evaporated and the crude product was passed through a short silica gel plug with CH2Cl2 as eluent, followed by recrystallization from MeOH to yield 9.59 g of pale yellow solid. Yield: 74%. 1H NMR (500 MHz, CDCl3, ppm): δ 1.97 (overlapped d, J=7.0 Hz, 12H, 4CH3), 4.17-4.37 (m, 8H, (4CH2), 4.52 (overlapped quartet, J=6.1 Hz, 4H, (4-CH). 13C NMR (125 MHz, CDCl3, ppm): 12.06-12.15 (4CH3), 23.40 (4CH), 43.57-44.59 (C(CH2)4), 63.11-63.15 (4CH2), 171.28-171.33 (4C═O).
Adipic acid (0.050 mol, 7.31 g) and SOCl2 (0.125 mol, 14.87 g, 9.1 mL) were refluxed (80° C.) until the evolution of HCl and SO2 neutralized in 5 M aqueous solution of NaOH ceased (approximately after 2 h). The excess of SOCl2 was removed under reduced pressure. The temperature of the reaction was increased to 85° C. and bromine (0.125 mol, 19.98 g, 6.4 mL) was added drop-wise over a period of 6 h followed by additional stirring at 85° C. until the disappearance of intermediates on 1H NMR spectrum. The reaction was complete in 3 h. The hot bromide derivative was subsequently added drop-wise to 80 mL of MeOH cooled at 0° C. with an ice-bath. The solution was warmed to room temperature overnight and poured into ice-water. The crude product was extracted into CH2Cl2. The organic layer was washed with 2% aqueous solution of Na2SO3 followed by the aqueous solution of NaHCO3 and water. The organic layer was separated and dried with Na2SO4. The solvent was evaporated and the product was recrystallized from MeOH to yield 12.94 g of white solid. Yield: 78%. 1H NMR (500 MHz, CDCl3, ppm): 2.09-2.11 (m, 2H, CH2), 2.32-2.34 (m, 2H, CH2), 3.82 (s, 6H, 2CH3), 4.27-4.30 (m, 2CH). 13C NMR (125 MHz, CDCl3, ppm): 32.66 (CH2CH2), 44.44 (2CHI), 53.31 (2OCH3), 169.82 (2C═O).
Adipic acid (0.050 mol, 7.31 g) and SOCl2 (0.125 mol, 14.87 g, 19.1 mL) were refluxed (80° C.) until the evolution of HCl and SO2 neutralized in 5 M aqueous solution of NaOH ceased (approximately after 2 h). The excess of SOCl2 was removed under reduced pressure. The temperature of the reaction was increased to 85° C. and bromine (0.125 mol, 19.98 g, 6.4 mL) was added drop-wise over a period of 2 h followed by additional stirring at 85° C. until the disappearance of the intermediate product in the 1H NMR spectrum. The reaction was complete in 4 h. The hot bromide was subsequently added drop-wise to 80 mL of MeOH cooled at 0° C. in an ice-bath. The solution was warmed to room temperature overnight and poured into ice-water. The crude product was extracted into CH2Cl2. The organic layer was washed with 2% aqueous solution of Na2SO3 followed by an aqueous solution of NaHCO3 and water. The organic layer was separated and dried with Na2SO4. The solvent was evaporated and the product was recrystallized from MeOH to yield 17.04 g of white solid. Yield: 81%. 1H NMR (500 MHz, CDCl3, ppm): δ 2.08-2.32 (m, 4H, CH2CH2), 3.39 (m, 6H, 2OCH3), 3.61-3.63 (m, 4H, 2OCH2), 4.26-4.31 (m, 2H, 2CH), 4.32-4.35 (m, 4H, 2CH2COO). 13C NMR (125 MHz, CDCl3, ppm): 32.40-32.60 (CH2CH2), 44.47-44.52 (2CHI), 59.25 (2OCH3), 65.24-65.26 (2CH2COO), 70.24 (2OCH2), 169.25 (2C═O).
To a solution of NaI (0.0405 mol, 6.07 g) in acetone (100 mL) at 25° C., a solution of dimethyl 2,5-dibromohexanedioate (DMDBH, 0.0135 mol, 4.48 g) in acetone (50 mL) was added rapidly. The precipitation of NaBr appeared after approximately 10-20 s. The reaction mixture was stirred until complete disappearance of DMDBH in the 1H NMR spectrum. The reaction was complete in 4 h. NaBr was filtered off, the solvent was evaporated and the crude product was passed through a short silica gel plug with CH2Cl2 as eluent, followed by recrystallization from MeOH to yield 4.53 g of white crystals. Yield: 79%. 1H NMR (500 MHz, CDCl3, ppm): 1.92-2.01 (m, 2H, CH2), 2.13-2.20 (m, 2H, CH2), 3.76 (s, 6H, 2CH3), 4.29-4.36 (m, 2CH). 13C NMR (125 MHz, CDCl3, ppm): 18.05-18.35 (2CHI), 35.66-35.85 (CH2CH2), 53.20 (2OCH3), 171.45 (2C═O).
To a solution of NaI (0.0225 mol, 3.37 g) in acetone (70 mL) at 25° C., a solution of bis(2-methoxyethyl) 2,5-dibromohexanedioate (BMEDBH, 0.0075 mol, 3.15 g) in acetone (30 mL) was added rapidly. The precipitation of NaBr appeared after approximately 10-20 s. The reaction mixture was stirred until complete disappearance of BMEDBH in 1H NMR spectrum. The reaction was complete in 2 h. NaBr was filtered off, the filtrate was diluted with water and product was extracted into CH2Cl2. The organic layer was separated washed with 2% aqueous solution of Na2SO3 followed by brine and water. The organic layer was separated and dried with Na2SO4. The solvent was evaporated and the crude product was purified on silica gel plug with hexane/ethyl acetate (9/1) as eluent. No recrystallization was possible due to the very low melting point of the product. However, the product solidified upon standing to yield 3.59 g of pale yellow solid. Yield: 93%. 1H NMR (500 MHz, CDCl3, ppm): δ 1.99-2.18 (m, 4H, CH2CH2), 3.40-3.41 (m, 6H, 2OCH3), 3.58-3.65 (m, 4H, 2OCH2), 4.27-4.33 (m, 4H, 2CH2COO), 4.33-4.37 (m, 2H, 2CH). 13C NMR (125 MHz, CDCl3, ppm): 18.22-18.55 (2CHI), 35.57-35.75 (CH2CH2), 59.22 (2OCH3), 64.98-64.99 (2CH2COO), 70.15 (2OCH2), 171.05-171.08 (2C═O).
Celvol 540 (0.293 g in 1 mL water stock solution), Methocel K100 (0.110 g in 1 mL water stock solution) and water (7 mL) were placed in a 50 mL Ace Glass 8648 #15 Ace-thred pressure tube equipped with bushing and plunger valve. The content of the tube was degassed by six freeze-pump-thaw cycles in acetone/dry ice. The tube was filled with nitrogen and frozen. Initiator (BIPE, 42.6 mg, 17.2 μL, 0.1 mmol), catalyst (Na2S2O4, 34.8 mg, 0.2 mmol), buffer (NaHCO3, 18.5 mg, 0.22 mmol) and precondensed VC (3.3 mL) were added. The tube was closed and degassed through the plunger by applying reduced pressure and filling the tube with nitrogen 20 times at −78° C. in an acetone/dry ice bath. The exact amount of vinyl chloride (VC) (˜2.2 g, 35.2 mmol) was determined gravimetrically by weighing the tube before the addition of precondensed VC and after degassing. After the content was degassed the tube was closed and the reaction mixture was stirred at 25° C.±0.5° C. The polymerization experiments were carried out in a hood behind a protective shield. After 6 h, the tube was slowly opened. In the case of intensive VC release the tube was frozen and then slowly opened. The excess of VC was allowed to evaporate and the suspension was filtered. The polymer was washed with water followed by methanol and dried in a vacuum oven at 25° C. to yield 0.47 g (21%) of white PVC powder with Mn=9,385 (value calibrated with Universal Calibration for PVC) and Mw/Mn=2.01.
The synthesis of bromo-terminated bifunctional and tetrafunctional initiators bis(2-bromopropionyloxy)ethane (BBPE) and pentaerythritol tetrakis(2-bromopropionate) (4BrPr) is outlined in Scheme 1. Both bifunctional and tetrafunctional initiators were prepared via acylation of ethylene glycol and pentaerythritol, respectively, with a stoichiometric amount of 2-bromopropionyl bromide in dry THF in the presence of dry pyridine. Triethylamine (TEA) also can be used. However, TEA mediates the formation of secondary products. The iodo-terminated derivatives were generated from the brominated initiators bis(2-iodopropionlyloxy) ethane (BIPE) and pentaerythritol tetrakis(2-iodopropionate) (4IPr) (Scheme 1) by the Finkelstein halogen exchange reaction33 with NaI in acetone at 25° C. Over 74% yield was obtained in 2 to 6 h of reaction at 25° C.
Few additional bifunctional initiators were also synthesized. Scheme 2 shows the synthesis of these bifunctional initiators.
One of the least expensive precursors for the synthesis of bifunctional initiators is adipic acid. Two iodo-terminated bifunctional initiators, dimethyl 2,5-diiodohexanedioate (DMDIH) and bis(2-methoxyethyl)-2,5-diiodohexanedioate (BMEDIH) were synthesized according to a modified literature method starting from adipic acid. See, Guha and Sankaran, Org Synth 1955, Coll Vol 3, 623-627. BMEDIH was synthesized for structural investigations since its 1H NMR resonances do not overlap with those of the backbone of PVC.
Both DMDIH and BMEDIH initiators were synthesized in four-steps two pot reaction. DMDIH and BMEDIH were prepared from commercially available adipic acid, which was converted to the corresponding acid chloride via treatment with thionyl chloride at ˜80° C. in bulk. Without further purification the acid chloride was brominated via drop-wise addition of Br2 at 85-90° C. These two steps were performed in one pot. Without further purification the product of the bromination was esterified with methanol and 2-methoxyethanol, respectively. For the purpose of mechanistic and structural studies the choice of these two alcohols was based on their 1H NMR spectra, that revealed the presence of chemical shifts associated with —CH2—OCH3 and —OCH3 groups in a region, which do not overlap with the backbone of PVC. This allows for an accurate analysis of the polymer structure. Both bromo-terminated bifunctional initiators were isolated and converted into iodo-terminated bifunctional initiators by the Finkelstein iodine exchange reaction. Percec, et al., J. Polym Sci Part A: Polym Chem 2005, 43, 773-778; The complete exchange of Br to I based on 1H NMR analysis was achieved in 2 to 4 h in acetone at 25° C. The pure products were obtained in higher than 79% yield after recrystallization from MeOH.
SET-DTLRP of VC Initiated with BIPE and Catalyzed by Na2S2O4
All kinetic experiments were carried out in 50 mL glass Ace Glass 8648 #15 high pressure tubes equipped with bushing and a plunger valve. Each data point on the kinetic plots represents a single experiment. All polymerizations were performed in water in the presence of two surfactants: polyvinyl alcohol (4.99% in H2O Celvol 540) and hydroxypropylmethylcellulose (4.20% in H2O Methocel K100). The surfactant were used in the ratio Celvol 540/Methocel K100=0.7 parts per monomer/0.2 parts per monomer in respect to VC. Thus, for 1 g of VC 0.007 g of solid Celvol 540 and 0.2 g of solid Methocel K100 were used. In addition, each polymerization was performed in the presence of NaHCO3 as a buffer, which maintains a basic pH of the reaction to prevent the decomposition of Na2S2O4 as well as to consume SO2 produced after the oxidation of SO2−.radical anion. SET-DTLRP of VC does not proceed in the absence of NaHCO3. The synthesis of this PVC is shown in Scheme 1a.
The two slopes corresponding to liquid-liquid emulsion and solid-liquid suspension polymerizations on the ln([M]0/[M]) versus time plot (
The efficiency of both DMDIH and BMEDIH bifunctional initiators is 79% which is similar to the efficiency of BIPE in the corresponding polymerization carried out at 25° C.
The structure of PVC obtained by SET-DTLRP of VC and initiated by BIPE bifunctional initiator was elucidated by a combination of one-dimensional (1D) 1H and 13C NMR spectroscopy and two-dimensional (2D) Heteronuclear Multiple Quantum Coherence (HMQC) methods.
The ˜CH3 groups of the initiator were detected at 1.22 ppm. The ˜CH2CH(CH3)C(O)O˜ groups as part of the PVC backbone next to the initiator partially overlap with the signal corresponding to ˜CH2˜backbone of the PVC. Finally the two signals at 5.92 ppm and 6.04 ppm were assigned to the stereoisomers r and m of ˜CHClI chain ends. The two chain ends are identical. Finally the 1H NMR analysis of the sample showed only very small levels of structural defects, which were recorded at 4.08 ppm (trans-CH═CHCH2Cl). The multiplets at 3.68-3.87 belong to ˜CH2Cl groups. The very weak signal at 5.76-5.88 represents the ˜CH═CH˜ moiety.
As can be seen in the collection of 1H NMR spectra of PVC samples obtained by the SET-DTLRP of VC initiated with BIPE at 25° C. in water (
The general structural features observed in the 1H NMR spectrum of PVC prepared by SET-DTLRP in water and initiated with DMDIH and BMEDIH are identical to PVC obtained in the polymerization initiated by BIPE and CHI3. The only observable difference in all samples are peaks representing various parts of initiators. Both
One of the primary advantages of the SET-DTLRP methodology its flexibility in the design of experiments for the synthesis of polymers with different topologies. Various polymer topologies are accessible via the structure of the initiator. SET-DTLRP was used in the preparation of four-arm star PVC using 4IPr as a tetrafunctional initiator (Scheme 1, 4IPr).
The kinetic data for the polymerization of VC with [VC]0/[4IPr]0=500 performed in water in the presence of Celvol 540 and Methocel K100 surfactants in the amounts used previously for the polymerization with bifunctional initiators and using Na2S2O4/NaHCO3 catalytic system are presented in
The kinetic data presented in
The structure of PVC obtained by SET-DTLRP initiated with the tetrafunctional 4IPr initiator is very similar to the PVC structures from the previous polymerizations performed with bifunctional initiators. The only difference consists in the presence of resonances corresponding to the tetrafunctional part of the initiator. The assignments of all peaks are shown in
The SET-DTLRP of VC initiated with various multifunctional initiators BIPE, DMDIH, BMEDIH and 4IPr provides PVC with identical and active chloriodomethyl chain ends that are suitable for further functionalization and block copolymerization. PVC obtained by this methodology are free of structural defects or contain them at the level of the resolution of the 1H NMR analysis. These difunctional and tetrafunctional PVC represent the first examples reported in the literature and are precursors for the synthesis of unprecedented ABA block copolymers and four arm-star block copolymers based on PVC that previously were not accessible by any other synthetic method.
Pentaerythritol tetrakis(2-iodopropionate) (4IPr) was synthesized by the sequence of reactions outlined in Scheme 1. The tetrafunctional initiator 4IPr was obtained by the esterification of pentaerythritol, with a stoichiometric amount of 2-bromopropionyl bromide in dry THF in the presence of dry pyridine, followed by the Finkelstein halogen exchange reaction with NaI in acetone at 25° C. A 74% yield was obtained in 6 h at 25° C. This initiator slowly decomposes upon standing at room temperature changing color to yellow. Preferably it should be freshly recrystallized from MeOH before polymerization.
4IPr initiator was used for the synthesis of the four-arm star PBA macroinitiator [PBACH(CH3)—CO—O—CH2]4C by the SET-DTLRP of BA initiated with 4IPr in water at 25° C. and catalyzed by Na2S2O4 (Scheme 4). The initial [BA]0/[4IPr]0 ratio used in this polymerization was 100. The polymerization was interrupted at 97% conversion to yield a four-arm star PBA with Mn=14,864 and Mw/Mn=1.642. 1H NMR analysis of this four-arm star PBA macroinitiator is shown in
The [PBA-CH(CH3)—CO—O—CH2]4C synthesized as shown in Scheme 4 was used as a macroinitiator (PBA-4IPr) for the synthesis of the [PVC-b-PBA-CH(CH3)—CO—O—CH2]4C four-arm starblock copolymer. The synthesis of this block copolymer is illustrated in Scheme 5. Three experiments were performed.
In the first experiment the initial ratio [VC]0/[PBA-4IPr]0 was 1,000 while in the second experiment this ratio was 5,000. Kinetic experiments of the block copolymerization were carried out in both cases (
The kinetic of the second block-copolymerization experiment was performed at 25° C. and is shown in
In the third experiment a ratio [VC]0/[PBA-4IPr]0 of 10,000 was used and only two data points were collected for the kinetic experiment. These data are reported in Table 3.
The structure of the four-arm star [PVC-b-PBA-CH(CH3)—CO—O—CH2]4C obtained by SETDTLRP of VC initiated with the four-arm star [PBA-C(CH3)—CO—O—CH2]4C macroinitiator was elucidated by 1H NMR spectroscopy. Two samples of the four-arm star [PVC-b-PBA-CH(CH3)—CO—OCH2]4C obtained at 29% and 46% conversion were analyzed by NMR and their structure is shown in
Tables 1, 2 and 3 summarize the structure of the four-arm star-block copolymers synthesized. As it can be observed from these tables the theoretical Mn of the four-arm star-block copolymer is always lower than the experimental value obtained by GPC calibrated with polystyrene standards. This result is expected since the hydrodynamic volume of a four-arm star-block copolymer is lower than that of the corresponding linear block copolymer. The Mn of PBA per arm in the four arm-star macroinitiator and four-arm star-block copolymer is 3,627. The Mn of the PVC segment per arm from the four-arm starblock copolymer varies between 353 and 33,622.
Pentaerythritol tetrakis(2-iodopropionate) was used as a tetrafunctional initiator for the Na2S2O4 catalyzed SET-DTLRP of n-butyl acrylate in water at room temperature. The resulting tetrafunctional poly(n-butyl acrylate) macroinitiator with Mn=14,864 or Mn=3,627 per arm was used to initiate the SET-DTLRP of vinyl chloride and provide four-arm star-block copolymers [PVC-b-PBA-CH(CH3)—CO—OCH2]4C. The Mn of the PVC segment from each arm of the four-arm star-block copolymer varied between 353 and 33,622. These experiments provide the first examples of thermoplastic elastomers based on four-arm star-block copolymers containing PBA as soft segment and PVC as hard segment.
This application claims benefit of U.S. Patent Application No. 61/120,085, filed Dec. 5, 2008, the disclosure of which is incorporated by reference herein in its entirety.
This invention was made using government support from National Science Foundation Grants DMR-0548559 and DMR-0520020. Accordingly, the United States Government may have certain rights in the invention described herein.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/US2009/066693 | 12/4/2009 | WO | 00 | 4/18/2012 |
| Number | Date | Country | |
|---|---|---|---|
| 61120085 | Dec 2008 | US |
