Use, to chemically stabilise a polymer matrix and/or to increase its durability when said polymer matrix is subjected to an oxidising reaction, of a polysiloxane network consisting of a chain of units identical or different and having the formula: X 1 -[-Si(X 2)(X 3)-O-] n -X 4 wherein the two radicals X 2 of two -Si(X 2)(X 3)-O- units of the network can be identical or different; the two radicals X 3 of two -Si(X 2)(X 3)-O- units of the network can be identical or different; the radicals X 1, X 2 and X 3 are, independently of each other, selected from the group consisting of a hydrogen; a halogen; an amine; a diamine; an amide; an acyl; a vinyl; a hydroxyl; an epoxy; an isocyanate; a carboxyl; a glycidoxy; an acryloxy such as a methacryloxy; an optionally substituted (hetero)alkyl; an optionally substituted (hetero)aryl group; a group having the formula X 1 -[Si(X 2)(X 3)-O-] n - and an alkoxyl group having the formula -OX 5 with X 5 representing an optionally substituted (hetero)alkyl group; the radical X 4 is selected from the group consisting of a hydrogen; a halogen; an amine; a diamine; an amide; an acyl; a vinyl; an epoxy; an isocyanate; a carboxyl; a glycidoxy; an acryloxy such as a methacryloxy; an optionally substituted (hetero)alkyl, an optionally substituted (hetero)aryl group and the salts thereof; n represents a whole number between 2 and 100000; and at least one radical selected from the radicals X 1, X 2 and X 3 is a functionalising group comprising at least one thiol function, no covalent bond existing between said polymer matrix and said functionalised polysiloxane network, said polymer matrix and said functionalised polysiloxane network being semi-interpenetrating or interpenetrating, said functionalised polysiloxane network being oxidised faster than said polymer matrix and having a sacrificial role and between 0% and 50% of the thiol stabilising functions initially present in the membrane comprising said polymer matrix and said functionalised polysiloxane network having been converted, by an oxidising treatment, into sulphonic functions, said oxidising treatment consisting in an oxidation in a solution of hydrogen peroxide in which the concentration of hydrogen peroxide is between 0.05 and 3% by weight relative to the total weight of the solution, at a temperature between 30 and 90°C. the two radicals X 2 of two -Si(X 2)(X 3)-O- units of the network can be identical or different; the two radicals X 3 of two -Si(X 2)(X 3)-O- units of the network can be identical or different; the radicals X 1, X 2 and X 3 are, independently of each other, selected from the group consisting of a hydrogen; a halogen; an amine; a diamine; an amide; an acyl; a vinyl; a hydroxyl; an epoxy; an isocyanate; a carboxyl; a glycidoxy; an acryloxy such as a methacryloxy; an optionally substituted (hetero)alkyl; an optionally substituted (hetero)aryl group; a group having the formula X 1 -[Si(X 2)(X 3)-O-] n - and an alkoxyl group having the formula -OX 5 with X 5 representing an optionally substituted (hetero)alkyl group; the radical X 4 is selected from the group consisting of a hydrogen; a halogen; an amine; a diamine; an amide; an acyl; a vinyl; an epoxy; an isocyanate; a carboxyl; a glycidoxy; an acryloxy such as a methacryloxy; an optionally substituted (hetero)alkyl, an optionally substituted (hetero)aryl group and the salts thereof; n represents a whole number between 2 and 100000; and at least one radical selected from the radicals X 1, X 2 and X 3 is a functionalising group comprising at least one thiol function, no covalent bond existing between said polymer matrix and said functionalised polysiloxane network, said polymer matrix and said functionalised polysiloxane network being semi-interpenetrating or interpenetrating, said functionalised polysiloxane network being oxidised faster than said polymer matrix and having a sacrificial role and between 0% and 50% of the thiol stabilising functions initially present in the membrane comprising said polymer matrix and said functionalised polysiloxane network having been converted, by an oxidising treatment, into sulphonic functions, said oxidising treatment consisting in an oxidation in a solution of hydrogen peroxide in which the concentration of hydrogen peroxide is between 0.05 and 3% by weight relative to the total weight of the solution, at a temperature between 30 and 90°C.