Dimethyl maleate is acts as a dienophile involved in ultrasonic irradiation promoted Diels-Alder reaction with substituted furans. It is widely used as an intermediate and additive for pharmaceuticals, copolymers, pigments, plastics, paints, adhesives and agrochemicals. As an internal modifier, it increases the glass transition temperature of styrene or vinyl chloride polymer. It plays a vital role to improve the hardness and toughness of polymer films such as copolymers of vinyl acetate.