Simultaneous separating template polymerizations of copolymers 4a and 4b obtained from 4-methylene-2-phenyl-2-(4-vinylphenyl)-1,3-dioxolanes with styrene were carried out. Polymerizable functional groups on the side chain of 4 underwent chain reaction with a free radical initiator to afford poly(oxotrimethylene) as a newborn polymer 7N accompanying release of copoly(vinylbenzophenone/styrene) as a template polymer 7T. The postpolymers 7N and 7T were divided by fractional precipitation without postchemical treatment. The efficiency of separation was estimated by the composition of polo(oxotrimethylene) as K % in the fraction. All K % values on this paper were higher than the K % value of the template polymerization employing the homopolymer of 4-methylene-2-phenyl-2-(4-vinylphenyl)-1,3-dioxolane. It was attributed to dilution of the local concentration by the comonomer segment, which excluded the ring-intact addition to afford a grafting point between the newborn and template polymers. The prepolymer 4b containing a methyl group on the dioxolane ring gave the most excellent K % value. GPC elution curves of the newborn polymer obtained from 4b indicated that the newborn polymer was given by complete separation from the template polymer simultaneously.