Crystalline-crystalline poly(3-hexylthiophene)-polyethylene diblock copolymers: Solidification from the melt

We report on the development of the solid-state structure from the melt of crystalline-crystalline diblock copolymers consisting of the semiconducting poly(3-hexylthiophene) (P3HT) and insulating polyethylene (PE) - a material combination that previously was shown to feature promising characteristics for applications in flexible organic electronics. The nature of the structures obtained from the melt was found to generally be dictated by crystallization of the PE block, which solidified after the P3HT sequence. This resulted in the formation of classical spherulitic structures for diblock copolymers of low P3HT content. At P3HT contents exceeding 10-20 wt%, the semiconductor block increasingly hampered crystallization of the PE moiety, with the P3HT entity arranging into columnar and at higher content into lamellar micelle-type domains. Unlike the rate of crystal growth of the two moieties, interestingly, the dimensionality of both entities of the diblock copolymers was found to be unaffected by the presence of the dissimilar block.