Polymeric products are disclosed that are suitable for application to fibrous substrates such as textiles, leather and paper, to impart oil (oleophobicity) and water repellent (hydrophobicity) properties to the treated material. The polymeric products comprise an amino-functional polysiloxane bonded through its amino groups to an addition copolymer of a fluoro-substituted alkyl ester of an olefinically unsaturated carboxylic acid and an olefinically unsaturated monomer having a functional group capable of reacting with the amino groups of polysiloxane and optionally one or more olefinically unsaturated comonomers.