Poly(ethylene oxide) functionalization
A simple procedure is provided by which the hydroxyl termini of poly(ethylene oxide) can be appended with functional groups to a useful extent by reaction and precipitation. The polymer is dissolved in warmed toluene, treated with an excess of organic base and somewhat less of an excess of a reactive acylating reagent, reacted for several hours, then precipitated in isopropanol so that the product can be isolated as a solid, and salt byproducts are washed away. This procedure enables functionalization of the polymer while not requiring laborious purification steps such as solvent-solvent extraction or dialysis to remove undesirable side products.
1. A method for preparing functionalized high molecular weight polyethylene oxide (HWPEO), comprising the steps of:
(a) dissolving the HWPEO in a first solvent and reacting the HWPEO with an organic base and an acylating reagent to form a mixture containing functionalized HWPEO, salt, unreacted organic base, and unreacted acylating reagent;
(b) combining the mixture with isopropanol or ethanol;
(c) allowing the functionalized HWPEO to precipitate while the salt, the unreacted organic base and the unreacted acylating reagent remain in a solution with the isopropanol or ethanol; and
(d) filtering the functionalized, salt-free HWPEO from the solution.
2. The method of claim 1 wherein the HWPEO has a molecular weight greater than 50 kDa.
3. The method of claim 1 wherein the HWPEO has a molecular weight greater than 100 kDa.
4. The method of claim 1 wherein the HWPEO has a molecular weight greater than 200 kDa.
5. The method of claim 1 wherein the HWPEO has a molecular weight greater than 500 kDa.
6. The method of claim 1 , further comprising, before step (a), an additional step of washing and then drying the HWPEO.
7. The method of claim 6 wherein the HWPEO is washed in one or more of ethyl acetate, acetone, and isopropanol.
8. The method of claim 1 wherein the first solvent is selected from the group consisting of isopropanol, benzene, anisole, acetonitrile, toluene, methylene chloride, chloroform, and xylene.
9. The method of claim 1 wherein the acylating reagent comprises a functional group selected from the group consisting of dyes, fluorescing groups, azido groups, acetylene groups, controlled radical polymerization initiators, reactive alkenes, aldehydes, and disulfide groups.
10. The method of claim 1 wherein the acylating reagent is selected from the group consisting of alkyl chloroformates, acyl chlorides, acyl bromides, acid anydrides, acyl nitriles, acyl cyanides, acyl azides, acyl imidazolates, acyl N-hydroxysuccinimidates, acyl 4-nitrophenolates, acyl pentafluorophenolates, sulfonyl chlorides, sulfonyl bromides, phosphoryl chlorides and phosphoryl bromides.
11. The method of claim 1 wherein the acylating reagent comprises 2-bromoisobutyryl bromide.
12. The method of claim 1 wherein the organic base is selected from the group consisting of triethylamine and tributylamine.
13. The method of claim 1 further comprising adding an esterification catalyst in step (a).
14. The method of claim 13 wherein the esterification catalyst comprises DMAP.
15. A method for preparing functionalized high molecular weight polyethylene oxide (HWPEO), comprising the steps of:
(a) dissolving the HWPEO in a solvent and reacting with 2-bromoisobutyryl bromide and triethylamine to form a mixture containing functionalized HWPEO, salt, unreacted 2-bromoisobutyryl bromide and unreacted triethylamine;
(b) combining the mixture with isopropanol;
(c) allowing the functionalized HWPEO to precipitate while the salt, unreacted 2-bromoisobutyryl bromide and unreacted triethylamine remain in a solution with the isopropanol; and
(d) filtering the functionalized, salt-free HWPEO from the solution.