Structural Anisotropy of Poly(alkylthiophene) Films

Abstract

The structural anisotropy of various poly(alkylthiophene) films have been studied by X-ray diffraction, using both conventional methods and synchrotron radiation at grazing incidence. Solutioncast films orient with the side chains preferably normal to the film surface, whereas spin-cast films of nonstereoregular material orient with both the main and the side chains in the film plane. For thick (10-50 µm) solution-cast films, the degree of orientation depends strongly on the solvent used for casting, and on the stereoregularity of the polymer, films of stereoregular materials being more oriented than those of nonregular materials. The most oriented nonregular films are those cast from mixtures of chloroform and tetrahydrofuran. Thin (50-500 nm) solution-cast films are more oriented than the thicker ones, and the effects of different stereoregularity or different casting solvents are small. For spin-cast films, the degree of orientation is independent of substrate and solvent. Spin-cast films of stereoregular material have two different phases: One with the side chains normal to the substrate, and another where they are parallel to the substrate. The diffraction peaks of spin-cast poly(octylthiophene) narrow considerably upon heating.

Diffraction analysis of highly ordered smectic supramolecules of conjugated rodlike polymers

“…Therefore, the reflection broadening is principally due to lattice parameter fluctuations (microstrains) and the actual crystallite size may be far higher. This order is better than that of PAT:s, such as poly(3-hexylthiophene) (P3HT) (Aasmundtveit et al, 2000), or P3DT (Prosa et al, 1999), or rodlike poly(oxy-1,4-phenyleneoxy-1,4-phenylenecarbonyl-1,4-phenylene) oligomers (Dupont et al, 2000).…”

“…Self-assembly, particularly in polyalkylthiophenes, (PAT), results in local order (Tashiro et al, 1991;Prosa et al, 1999;Aasmundtveit et al, 2000) related to improved electronic characteristics, such as high photoluminescence quantum yield (PLQY) (Theander et al, 1999) or charge carrier mobility (Sirringhaus et al, 1999). However, the coiling of PAT resists liquid crystal (LC) and high overall order, and the covalently bonded side chains are permanent.…”

Molecular-weight dependence of interchain polaron delocalization and exciton bandwidth in high-mobility conjugated polymers

“…Similar effects have previously been reported for differences in stereoregularity, spin/drop casting, and choice of solvent. [30][31][32] The polymers spin cast from chloroform tend to have a bimodal orientation distribution with a significant fraction of microcrystalline grains oriented with the a axis in plane. 31 This is also evidenced by rocking scans of the 100 reflection ͓Fig.…”

“…[30][31][32] The polymers spin cast from chloroform tend to have a bimodal orientation distribution with a significant fraction of microcrystalline grains oriented with the a axis in plane. 31 This is also evidenced by rocking scans of the 100 reflection ͓Fig. 4͑b͔͒ which show that the crystallites exhibit a doublepeaked texture with side chains preferentially oriented either perpendicular or parallel to the substrate, but less preferrably at intermediate angles.…”

An experimental study on the molecular organization and exciton diffusion in a bilayer of a porphyrin and poly(3-hexylthiophene)

“…[23][24][25][26][27] The organization of polyalkylthiophene backbones has been observed to strongly affect charge transport 22,24 and may also influence the extent of exciton diffusion. In this work, the photophysical and morphological properties of a combination of the visible-light absorbing electron-accepting porphyrin derivative meso-tetrakis ͑n-methyl-4-pyridyl͒ porphyrin tetrachloride ͑H 2 TMPyP͒ and regioregular poly͑3-hexylthiophene͒ ͑P3HT͒ are presented.…”