Method for preparing multi-arm poly(ethylene glycol) chlorides

1. A method for making a composition comprising at least one multi-arm PEG chloride having from 3 to about 10 arms comprising the steps of:

a) reacting at a temperature of less than or equal to about 100° C., optionally in the presence of a solvent, thionyl chloride and at least one multi-arm PEG polyol having from 3 to about 10 arms, to form a multi-arm PEG chloride having at least about 95% of hydroxyl end groups of the multi-arm PEG polyol converted to chloride end groups; and

b) separating the multi-arm PEG chloride from unreacted thionyl chloride and the optional solvent.

2. A method according to claim 1 wherein the reacting of step (a) is at a temperature of about 0° C. to about 100° C.

3. A method according to claim 1 wherein the reacting of step (a) is at a temperature of about 20° C. to about 100° C.

4. A method according to claim 1 wherein the reacting of step (a) is done for a time of about 2 hours to about 24 hours.

5. A method according to claim 1 wherein the optional solvent is selected from the group consisting of toluene, benzene, xylene, chlorobenzene, dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethylene, trichloroethylene, perchloroethylene, 1,2-dichloroethane, 1,1,1-trichloroethane, diethyl ether, diisopropyl ether, tetrahydrofuran, dioxane, acetone, methyl ethyl ketone, methyl isobutyl ketone, N,N-dimethylformamide, N,N-dimethylacetamide, and mixtures thereof.

6. A method according to claim 1 wherein the separating of step (b) is done by removing the thionyl chloride and the optional solvent by evaporating under reduced pressure.

7. A method according to claim 1 wherein the multi-arm PEG polyol is selected from the group consisting of an 8-arm star PEG polyol, a 6-arm star PEG polyol, and a 4-arm star PEG polyol.

8. A method according to claim 1 wherein the reacting of step (a) is done in the presence of a catalyst.

9. A method according to claim 8 wherein the catalyst is selected from the group consisting of an N,N-dialkylformamide, an iron(III) salt and mixtures thereof.

10. A method according to claim 9 wherein the N,N-dialkylformamide is selected from the group consisting of N,N-dimethylformamide, N,N-diethylformamide, N-formylmorpholine, N-formylpiperidine, and N-formylpyrrolidine.

11. A method according to claim 9 wherein the iron (III) salt is selected from the group consisting of ferric chloride, ferric oxide, and ferric sulfate.