Abstract
We experimentally observe a significant improvements in polariton lifetime through isotopic enrichment of hexagonal boron nitride (hBN). Commensurate increases in the polariton propagation length are demonstrated via direct imaging of polaritonic standing waves by means of infrared nano-optics, with resolution greater than \lambda/125 observed in a preliminary hyperlens design. Our results provide the foundation for a materials-growth-directed approach aimed at realizing the loss control necessary for the development of next generation PhP-based nanophotonic devices.