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

1. A method for making a composition comprising at least one multi-arm PEG amine 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;

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

c) forming a reaction mixture by reacting the multi-arm PEG chloride with either aqueous ammonia or anhydrous ammonia for a time and at a temperature to form a reaction product in which at least about 95% of the chloride end groups of the multi-arm PEG chloride are converted to amine end groups, thereby generating HCl, the aqueous ammonia or the anhydrous ammonia being in sufficient quantity to prevent gelation of the reaction mixture;

d) optionally, either removing HCl from the reaction product or converting the HCl to a salt by the addition of a base and removing said salt; and

e) optionally removing water from the reaction product of (c) or the product of step (d).

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 f 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.

12. A method according to claim 1 wherein the forming a reaction mixture of step (c) is done by reacting the multi-arm PEG chloride with aqueous ammonia at a temperature of about 60° C. to about 100° C. for a time of about 4 hours to about 48 hours.

13. A method according to claim 12 wherein the aqueous ammonia is concentrated aqueous ammonia having a concentration of about 28% by weight.

14. A method according to claim 1 wherein the forming a reaction mixture of step (c) is done by reacting the multi-arm PEG chloride with anhydrous ammonia at a temperature of about 60° C. to about 100° C. for a time of about 4 hours to about 48 hours.

15. A method according to claim 1 wherein the HCl is optionally removed from the reaction product using an ion exchange process with a strongly basic anion exchange resin in the hydroxide form.

16. A method according to claim 1 wherein the base used to convert the HCl to a salt in step (d) is selected from the group consisting of potassium carbonate, sodium carbonate, lithium carbonate, potassium hydroxide, sodium hydroxide, lithium hydroxide, potassium bicarbonate, sodium bicarbonate, and lithium bicarbonate.

17. A method according to claim 1 wherein the salt is optionally removed from the reaction product using a method selected from the group consisting of solvent extraction, precipitation, dialysis, and ultrafiltration.

18. A method according to claim 1 wherein the water is optionally removed from the reaction product of (c) or the product of step (d) using a method selected from the group consisting of lyophilization, ultrafiltration, and spray drying.