Method for the preparation of copolymers of alkyl methacrylates and maleic anhydride

A method, comprising:

• adding a feed solution comprising one or more alkyl methacrylates and a second portion of a radical initiator to an initial reaction solution comprising maleic anhydride, a first portion of the radical initiator, and a solvent;
• solution polymerizing the one or more alkyl methacrylates and the maleic anhydride in the presence of the solvent and the first and second portions of the radical initiator;
• and
• adding a third portion of the radical initiator to the one or more alkyl methacrylates and the maleic anhydride being subjected to the solution polymerization in the presence of the solvent and the first and second portions of the radical initiator, to obtain a sulfur-free copolymer comprising alkyl methacrylate monomer units and maleic anhydride monomer units,
• wherein the sulfur-free copolymer has a number average molecular weight in the range of 4000 to 18000 g/mol and a polydispersity index in the range of 1 to 5, and
• wherein a molar ratio of the one or more alkyl methacrylates to the maleic anhydride in the sulfur-free copolymer is in a range of from 10:1 to 1:1, based on a total molar amount of the one or more alkyl methacrylates and the maleic anhydride employed to prepare the sulfur-free copolymer.