Abstract: A B stageable thermosettable composition containing at least one polyepoxide and at least one linear anhydride monomer capable of forming a cyclopolymer in situ and processes for the formation of the B stage intermediate and final thermoset having a high service temperature is provided. The composition is useful in a two stage process; first to form a storage stable, flowable thermoplastic B stage intermediate by the free radical initiated vinyl polymerization of the linear anhydride in the liquid composition to a cyclic polymer and secondly to react the cyclic polymer with the poly epoxide to form a crosslinked high service temperature thermoset useful in the preparation of laminates, such as printed circuit boards, adhesives and encapsulants.