Ring-opened polynorbornenes

The invention provides a ring-opened polynorbornene that is relatively low in birefringence, has specific wavelength dependency about birefringence and is excellent in transparency and heat resistance. [Solving means] The polymer of the present invention has a structural unit (I) of the general formula (I): [Chemical formula 1 ] wherein in the general formula (I), m and n are integers of 0 to 2, X1 is an ethylene or vinylene group, R1 and R2 are individually a hydrogen atom or a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms, and R3 is a group of the general formula (I-1) or (I-2), in which in the general formulae (I-1) and (I-2), R11 to R27 are individually a hydrogen atom; a halogen atom; a substituted or unsubstituted hydrocarbon group having 1 to 30 carbon atoms, which may have a linkage containing or not containing oxygen, sulfur, nitrogen and/or silicon atom(s); or a polar group, p and q in the general formula (I-1) are individually 0 or a positive integer, with the proviso that when both p and q are 0, R12 and R15, or R19 and R15 may be bonded to each other to form a carbon ring or heterocyclic ring, and the carbon ring or heterocyclic ring may be either a monocyclic structure or a polycyclic structure, and s in the general formula (I-2) is 0 or a positive integer.