(poly)ester and (poly)amide compositions, method for modifying (poly)esters or (poly)amides and catalyst therefor

A composition comprising

• A) at least one (poly)ester or (poly)amide or combinations thereof, and
• B) at least one polymer comprising a structural unit of formula (I)
• —(CH2—CR3Z)o— (I)
• wherein
• o is a positive integer of at least 1,
• R3 is selected from the group of hydrogen, halogen, C1-C18 alkyl or C1-C18 alkyl substituted with one or more substituents independently selected from the group of hydroxy, carboxy, acyloxy, OR′, O2CR′, and CO2R′,
• R′ is selected from the group of optionally substituted C1-C18 alkyl, optionally substituted C2-C18 alkenyl, optionally substituted aryl, substituted heterocyclyl, optionally substituted aralkyl, optionally substituted alkaryl, wherein said optional substituents are selected from the group consisting of epoxy, alkoxycarbonyl, aryloxycarbonyl, isocyanato, cyano, silyl, halo and dialkylamino,
• Z is a group -BG-Cat+ M,
• BG is a covalent bond or a divalent bridge group,
• Cat+ is a one-time positively charged cationic residue selected from the group of one-time positively charged heterocyclic residues having one, two or three ring nitrogen atoms and optionally one ring oxygen atom, one ring sulfur atom, one ring phosphorus atom, one ring arsenic atom or one ring antimony atom, ammonium cations, phosphonium cations, arsonium cations or antimonium cations covalently attached to BG,
• M is a negatively i-charged counter-ion of type Ani− which is selected from the group of organic or inorganic anions, wherein Ani− will interact with one or more cationic residues Cat+ for charge-compensation in polymer B), and
• i is an integer from 1 to 4.