A chemical reaction system suitable for forming a polymeric biomaterial, a chemical reaction system comprising a first biomaterial precursor component and a second biomaterial precursor component, and means for mixing at least the first and second biomaterial precursor components, where in a reaction site, the first precursor component reacts much faster with the second precursor component than with other components in the mixture and the second precursor component reacts much faster with the first precursor component than with other components in the mixture, the first precursor component it comprises at least two nucleophiles which are more nucleophiles than H2O at physiological pH, the nucleophiles being selected from the group of thiols, thiol containing groups, amines and amine containing groups, the second precursor component comprises at least two conjugated unsaturated bonds or unsaturated groups conjugates, where said in conjugated laces or unsaturated groups are not maleimide or vinyl sulfones, and also in which the biomaterial is a material that is suitable for contact with the body of an animal, either on the surface of the animal or implanted within it, and that does not include raw albumin.Sistema de reacción química adecuado para formar un biomaterial polimérico, sistema de reacción química que comprende un primer componente precursor de biomaterial y un segundo componente precursor de biomaterial, y medios para mezclar al menos el primer y el segundo componentes precursores de biomateriales, donde en un sitio de reacción, el primer componente precursor reacciona mucho más rápido con el segundo componente precursor que con otros componentes en la mezcla y el segundo componente precursor reacciona mucho más rápido con el primer componente precursor que con otros componentes en la mezcla, el primer componente precursor comprende al menos dos nucleófilos que son más nucleófilos que H2O a pH fisiológico, siendo los nucleófilos seleccionados del grupo de t
