a composition , prepolymer and method to produce a polymer based on biodegradable or essentially renewable crude materials , which can be crosslinked by free radicals . the composition is based on polyesters that are functionalized with unsaturated monomer units , in a way that unsaturated groups can be located along the polymer main chain as well as at the ends of the prepolymer . in connection to the product production , the prepolymer is exposed to free radicals that leads to network formation . the composition of the crosslinked biopolymer can be adjusted from a stiff engineering material to an elastic rubbery material . the new biopolymer can be used in composite materials , dispersions , barrier materials , rubbery materials , biomedical applications , and the like .