Embodiments in accordance with the present invention encompass copolymers and terpolymers of a variety of polycycloolefinic monomers at least one of which monomer contains an additional unpolymerized ethylenic bond. In further aspect of this invention there is provided an embodiment encompassing compositions containing the polymers of this invention, a crosslinker, a free radical initiator, a tackifier and one or more suitable additives. The compositions of this invention can be formed into a variety of three-dimensional insulating articles upon exposure to suitable high temperature, such as for example films. The objects formed from the compositions of this invention exhibit hitherto unattainable low dielectric constant and low-loss properties, and very high thermal properties. The compositions of this invention may additionally contain one or more organic or inorganic filler materials, which provide improved thermo-mechanical properties in addition to very low dielectric properties. The compositions of this invention are useful in various applications, including as insulating materials in millimeter wave radar antennas, among others.