monomer such as butadiene, isoprene, cyclopentadiene, or dicyclopentadiene,--(a), (b) and (c) each being free radical polymerizable; and (d) a C.sub.5 -C.sub.20 cycloalkene like cyclopentene, cycloheptene, bicyclo(2.2.1)-hept-2-ene, namely NB, which may