On the way to the design of a new molecule for possible ambipolar organic field effect transistors, we discovered a crystal-­to-­crystal, essentially quantitative, monomer to polymer transformation. The crystalline polymer had the further interesting property of full exfoliation making it possible to isolate and observe a single polymer molecule. We further discovered preparation and X-­ray crystallographic characterization of the first crystalline homoatomic polymer chain as part of a semiconducting pyrroloperylene-­iodine complex. The crystal structure contains infinite polyiodideI I∞δ-­‐ and close similarities in the low-­wavenumber Raman spectra of the title compound and starch-­iodine complex suggest such infinite chains of polyiodide in the latter as well. The structure of iodine within the insoluble, blue starch-­iodine complex has remained elusive since the phenomenon was first observed over two centuries ago, and has since generated much speculation as to how iodine arranges within this complex. This includes suggestions of infinite polymeric iodine chains stabilized by amylose sugars.