The invention is related to the preparation of an ionic polymer composite material comprising a protein and carbohydrate-containing vegetable material component that serves as a reinforcement agent for the composite. In preferred embodiments of the invention, the vegetable seed component is selected from the group of soy spent flakes, defatted soy flour, or soy protein concentrate with ionic polymers and the ionic polymer is carboxylated poly(styrene-butadiene). The composites have a significantly higher elastic modulus when compared with base polymer.