Biodegradable graft polymers

A graft polymer comprising:

• (A) a block copolymer backbone as a graft base, wherein said block copolymer backbone (A) is obtainable by polymerization of at least two monomers selected from the group consisting of ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, 1,2-pentene oxide or 2,3-pentene oxide, wherein the number (x) of individual blocks within the block copolymer backbone (A) is an integer, wherein x is from 3 to 10, and
• (B) polymeric sidechains grafted onto the block copolymer backbone, wherein said polymeric sidechains (B) are obtainable by polymerization of at least one vinyl ester monomer (B1) and optionally N-vinylpyrrolidone as optional further monomer (B2);
• wherein the block copolymer backbone (A) has a structure according to formula (A2) with formula (A2) defined as follows:
• with
• o is an integer in the range of 2 to 100, and
• p is an integer in the range of 2 to 100.