Copolymerization of ethylene and cycloolefin isomerized from endo-form to exo-form

A cycloolefinic random copolymer:

• (1) which is a copolymer formed from ethylene and an isomer mixture of up to 80 mol % of a cycloolefin having an endo form with at least 20 mol % of the cycloolefin having an exo form, the cycloolefin having the following formula (I) ##STR34## wherein R.sup.1 to R.sup.14 are independently a hydrogen atom, a halogen atom or a hydrocarbon group, R.sup.15 to R.sup.18 are independently a hydrogen atom, a halogen atom or a hydrocarbon group, or R.sup.15 or R.sup.16 and R.sup.17 or R.sup.18 may be bonded to each other to form a monocyclic or polycyclic group, or R.sup.15 and R.sup.16 or R.sup.17 and R.sup.18 may together form an alkylidene group only when n is 1, n is 0 or 1, and m is 0 or a positive integer, provided that m and n cannot be simultaneously zero,
• (2) which has, based on a total of polymer units derived from the cycloolefin and polymer units derived from the ethylene, 10 to 90 mol % of the polymer units derived from the cycloolefin and 90 to 10 mol % of the polymer units derived from the ethylene,
• (3) wherein the polymer units derived from the cycloolefin have the following formula (II) ##STR35## wherein R.sup.1 to R.sup.18, n and m are as defined as above, and (4) which has an intrinsic viscosity (.eta.), measured in decahydronaphthalene at 135.degree. C., of 0.05 to 10 dl/g.