Abstract: The present invention relates to a stable storable composition for the chemical grafting of at least one filler comprising a hydroxyl group, onto a polymer. The composition according to the invention comprises at least one organic carboxylic acid comprising a carbon/carbon double bond that forms a resonance structure with the carbon/oxygen double bond of the carboxyl group, said composition being characterized in that it comprises a dispersing agent of the polyethylene oxide-based block polymer or copolymer type. The invention also relates to a process for chemical grafting of an organic acid onto a filler comprising at least one hydroxyl group, using said composition, so as to obtain a polymerizable liquid mixture.