The invention describes a composition containing a) a functionalized polymer (10) that comprises at least one polyester segment (13) and at least one, in particular at least two, polymer aggregating segment (11, 12) capable of forming non-covalent bonds based on a supramolecular interaction, b) an aggregating additive (20) that comprises at least one additive aggregating segment (21) capable of forming non-covalent bonds based on the same supramolecular interaction as the polymer aggregating segments (11, 12), wherein the polymer aggregating segments (11, 12) and the additive aggregating segment (21) are ditopic, wherein the polymer aggregating segments (11, 12) and the additive aggregating segment (21) are designed such that they can form aggregates (31) that contain polymer aggregating segments (11, 12) and additive aggregating segments 21, and wherein the polyester segment (13) has a number average molecular weight of from 10'000 g/mol to 50'000 g/mol. The invention also describes a functionalized polymer (10) that comprises at least one polyester segment (13) and at least two polymer aggregating segments (11, 12) capable of forming non-covalent bonds based on a supramolecular interaction, wherein the polymer aggregating segments (11, 12) are ditopic and designed such that they can form aggregates and wherein the polyester segment (13) has a number average molecular weight of from 10'000 g/mol to 50'000 g/mol. The invention also describes a method for the preparation of sheets, films, fibers, or molded parts from the composition or the functionalized polymer (10) according to the invention, sheets, films, fibers, or molded parts comprising a composition or a functionalized polymer (10) according to the invention, and the use of the composition according to the invention for the preparation of sheets, films, fibers, or molded parts.