A copolymer based on olefinic sulphonic acids as monomer component a) and an organosilicone-containing compound as reactive component b) is proposed, for which in particular 2-acrylamido-2-methylpropanesulphonic acid (AMPS.RTM.) is suitable as component a) and vinyltrimethoxysilane, vinyltriethoxysilane and trichlorosilane as component b). This copolymer, which may have a molecular weight of from 5,000 to 5,000,000 g/mol, may also comprise further reaction components c) and d) in addition to the two main components for which further reaction components (meth)acrylamides or vinyl ethers are suitable. These copolymers, which are obtainable in particular by precipitation or gel polymerizations, are used in particular in applications in construction chemistry and here especially as water retention agents and fluid loss additives in drilling fluids and for well cementing. The novel copolymers are distinguished by pronounced thermal stability, which is displayed especially under difficult pressure conditions and at high salinities.

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