Molecular structure of stretch oriented poly(3-hexylthiophene) studied by an extended X-ray diffraction mapping

Abstract

Detailed x-ray diffraction intensity mapping of the reciprocal space of stretched poly(3-hexylthiophene) films enabled us for the first time to reveal reflections associated with the stretch direction ( l = 1−7). The reflections are located at finite angles to the stretch axis and can therefore only be indexed on a monoclinic (or triclinic) unit cell. The monoclinic cell parameters are a=16.90 A ̊ , b=4.85 A ̊ , c=7.84 A ̊ , α=50.6° , ( a=4.85 A ̊ , b=16.90 A ̊ , c=7.84 A ̊ and β=129.4° by crystallographic conventions) and with two monomer units per cell. The values of a and c are directly measured whereas b and α are refined from structure factor calculations. Existence of h00 but absence of hk0, h0l and hkl reflections indicate layer disorder between oblique bc planes, whereas structure factor calculations indicate side chain disorder.