A method for preparing a copolymer that involves polymerizing at least one branched alkene monomer and at least one olefin monomer having a pendant benzocyclobutene (BCB) group to form a copolymer comprising a random distribution of a plurality of constitutional units corresponding to the at least one branched alkene monomer and the at least one olefin monomer. The polymerizing includes a carbocationic polymerization reaction involving sequential addition of a plurality of mixtures without terminating the carbocationic polymerization reaction, wherein the plurality of mixtures includes a mixture that includes the at least one branched alkene monomer and does not include the at least one olefin monomer having a pendant BCB group and a mixture that includes both the at least one branched alkene monomer and the at least one olefin monomer having a pendant BCB group. The copolymer composition can undergo crosslinking at elevated temperatures (preferably above 180° C.).