A polymer composition comprises (a) greater than 50 wt % (based upon the weight of the composition) of a cyclic olefin copolymer comprising at least one acyclic olefin and at least 20 weight % of one or more cyclic olefins (based upon the weight of the cyclic olefin copolymer), wherein at least a portion of the cyclic olefin copolymer has a glass transition temperature of greater than 150° C.; and (b) less than 50 wt % (based upon the weight of the composition) of an acyclic olefin polymer modifier, at least a portion of the modifier having a glass transition temperature of less than −30° C.; and no portion of the modifier having a softening point greater than +30° C., wherein the Bicerano solubility parameter of the modifier being no more than 0.6 J0.5/cm1.5 less than the Bicerano solubility parameter of the cyclic olefin copolymer. The polymer composition has a notched Izod impact resistance measured at 23° C. of greater than 500 J/m and a heat distortion temperature measured using a 0.46 MPa load of greater than 135° C.