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xqy2009金虫 (正式写手)
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[交流]
【求助】功能性PEG的合成
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我想合成一系列功能性修饰的PEG，如a-羟基-w-羧基聚乙二醇，在网上看了下报价，一克要1500元，哪位大哥能提供的合成思路呢 [ Last edited by zhangwj on 2009-3-29 at 12:19 ] |
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huquan0_0
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yusen_1982(金币+1,VIP+0):欢迎应助 4-2 11:53
薰衣草儿(金币+1,VIP+0):谢谢，辛苦了~ 6-11 11:02
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薰衣草儿(金币+1,VIP+0):谢谢，辛苦了~ 6-11 11:02
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Preparation of .alpha.-carboxylic-.omega.-hydroxyl polyethylene oxide HOOC--(CH.sub.2).sub.3--O-- (CH.sub.2CH.sub.2O).sub.n--CH.sub.2CH.sub.2OH Intitiator: 4-hydroxy butyric acid-sodium/potassium salt (K/NaOCO--CH2CH2CH2OK/Na) Synthesis of the polymer is involved three steps: (1) Initiation of ethylene oxide monomer (2) Propagation of ethyene oxide monomers and (3) termination of polymerization. Polymerization of ethylene oxide was carried out in a high pressure reactor (Par reactor) equipped with a magnetic driven mechanical stirrer. The reactor was bubbled with dried argon. Initiator was prepared separately in a three necked 1 L flask equipped with magnetic stirrer and a condenser with three way stopcock. 4-hydroxy butyric acid-sodium salt (5.7 g 0.045 mol) obtained from Fluka Chemical Co was used as received (it contain <0.5% water) added to the flask followed by addition of freshly cut potassium (1.8 g 0.046 mol). After addition of the solid content the flask was evacuated followed by pressurizing (30 psi) with argon. Dried tetrahydrofuran (THF) 400 ml was added and the solution was refluxed for 12 h. A heterogeneous solution is formed. This solution was transferred to high pressure Par reactor under a flow of argon using 12 gauge double tip stainless steel needle. The reactor temperature was lowered to -10.degree. C. Freshly distilled ethylene oxide (50 ml) (distilled over n-butyllithium) was added using stainless steel capillary. The solution was stirred at 50.degree. C. for 24 h. The reactor temperature cool to water bath temperature and the reactor content was poured into a glass beaker containing HCl (5 ml of 35% aqueous solution). A slight yellow color solution is formed with the precipitation of salt (KCl). Solution was filtered and the filtrate precipitated in cold 2-propanol containing 20% hexanes, giving the desired product as a light yellow precipitate which is dried in vacuo overnight. Yield 38 g (86.3%). In an Erlenmeyer flask equipped with a magnetic stir bar, obtained polymer from the preceding step was added to 500 ml distilled deionized water and stirred to dissolve followed by addition of dichloromethane to extract the polymer and to remove the unreacted initiator and residual amount of salt present. The solution was washed with deionized water two times than the dichloromethane solution was concentrated in rotavapor. The product finally reprecipitated in cold diethyl ether. The product was dried in vacuo overnight. Yield: g, 88%. .sup.1H-NMR (CDCl.sub.3) 2.35 ppm (m, --CH2 2H adjacent to COOH), 3.60 ppm (s, PEG backbone, 77H), 4.37 ppm (t, OH, 1H). .sup.1H NMR spectrum is reported in FIG. 1. Size exclusion chromatography (SEC) was carried out on a Varian liquid chromatograph equipped with a refractive detector. Three columns from Supelco (G6000-4000-2000 HXL) were used with THF as the eluent. The columns were calibrated with monodisperse polyethylene glycol standards. The molecular weight and the polydispersity indice were calculated. The SEC analysis of the product indicating Mn of 440 MwMn 1.16. The SEC trace is reported in FIG. 2. The value calculated from H NMR indicates Mn 1070. This indicating some interaction of the heterofunctional PEG with the packing materials of the column that resulting the retardation of the elution therefore underestimating the molecular weight of the polymer. |
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