Highly pure amphiphilic copolymer comprising hydrophobic block from alpha-hydroxy acid and process for the preparation thereof

1. A method for preparing an amphiphilic block copolymer comprising a hydrophobic polymer block of a poly(α-hydroxy acid), the method comprising the steps of:

dissolving an amphiphilic block copolymer comprising a hydrophobic polymer block of a poly(α-hydroxy acid) into a water-miscible organic solvent;

mixing a resultant polymer solution with water or an aqueous solution containing an alkali metal salt for 10 minutes to 24 hours to hydrolyze unreacted monomers contained in the amphiphilic block copolymer, wherein the alkali metal salt is sodium bicarbonate, sodium carbonate, potassium bicarbonate, potassium carbonate or lithium carbonate; adding sodium chloride or potassium chloride to the resultant solution in order to separate the solution into an organic solvent layer and an aqueous layer via salting out; and collecting the organic solvent layer and removing the organic solvent therefrom to recover a polymer, wherein the steps are performed sequentially.

2. The method according to claim 1 , wherein the hydrophobic polymer block of a poly(α-hydroxy acid) is one or more of hydrophobic block selected from the group consisting of polylactide, polyglycolide, poly(mandelic acid), polycaprolactone or poly(dioxan-2-one), copolymers thereof, polyaminoacids, polyorthoesters, polyanhydrides and polycarbonates.

3. The method according to claim 1 , wherein the amphiphilic block copolymer is represented by Formula 1:

HO—[R 1 ] l —[R 2 ] m —[R 3 ] n —R 4   [Formula 1]

wherein

R 1 is —CHZ—C(═O)—O—;

R 2 is —CHY—C(═O)—O—, —CH 2 CH 2 CH 2 CH 2 CH 2 —C (═O)—O— or —CH 2 CH 2 OCH 2 —C(═O)—O—;

R 3 is —CH 2 CH 2 O—, —CH(OH)—CH 2 —, —CH(C(═O)—NH 2 )—CH 2 — or

R 4 is —CH 3 or —C(═O)—[R 1 ] l —[R 2 ] m —CHZ—OH;

each of Z and Y is —H, —CH 3 , —C 6 H 5 or C 6 H 5 —CH 2 —;

each of l and m is an integer of 0-300, with the proviso that both l and m are not 0 at the same time; and

n is an integer of 4-1,100.

4. The method according to claim 1 , wherein the amphiphilic block copolymer has a number average molecular weight of 1,000 Daltons to 50,000 Daltons.

5. The method according to claim 1 , wherein the amphiphilic block copolymer comprises 20 wt %-95 wt % of a hydrophilic polymer.

6. The method according to claim 1 , wherein the aqueous alkali metal solution or water is added in an amount corresponding to 0.5 to 5 times of the volume of the organic solvent.

7. The method according to claim 1 , wherein sodium chloride or potassium chloride is added in an amount of 0.1 wt %-50 wt % based on the total weight of the amphiphilic block copolymer.

8. The method according to claim 1 , which further comprises, after recovering the polymer:

dissolving the polymer recovered after removing the organic solvent into an anhydrous organic solvent, followed by filtering, to obtain a solution containing the polymer; and

removing the organic solvent from the solution containing the polymer.