Poly(4-methyl-1-pentene) (P4MP) was characterized to evaluate its viability as a high-temperature dielectric film for capacitors. Detailed investigation of thermal, mechanical, rheological, and dielectric properties was carried out to assess its high-temperature performance and processability. P4MP was melt-processable below 270 degrees C without degradation and application temperatures as high as 160-190 degrees C can be achieved. The dielectric constant and loss of melt-processed P4MP films was comparable to biaxially oriented polypropylene (BOPP) capacitor films, although the dielectric strength was lower. Enhancements in dielectric strength up to 250-300% were achieved via solution-processing P4MP films, which could be easily scaled up on a roll-to-roll platform to yield isotropic, free-standing films as thin as 3-5m. The influence of crystal structure, crystallinity, and surface morphology of these films on the dielectric properties was examined. The dielectric strength was further increased by 450% through biaxial stretching of solution-cast films, and a Weibull breakdown field of 514V/m was obtained. The dielectric constant was very stable as a function of frequency and temperature and the dielectric loss was restricted to <1-2%. Overall, these results suggest that BOP4MP is a promising candidate to obtain similar energy density as a BOPP capacitor film but at much higher operating temperatures. (c) 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1497-1515