Blend Morphology in Polythiophene–Polystyrene Composites from Neutron and X-ray Scattering

Abstract

In this work, contrast-variation small-angle and ultra-small-angle neutron scattering are used together with wide-angle X-ray scattering (WAXS) to characterize the bulk molecular conformation and self-assembly of polythiophene-based conjugated polymers (CPs) in bulk blends with deuterated polystyrene (PS-d 8) as the matrix component. A significant and sharp transition from small to large globular domains is observed in the phase-separated morphology of all blends as a function of CP concentration. Evidence of self-assembly into nanofiber networks is also observed in regio-regular poly­(3-hexylthiophene) (RRe-P3HT) blends and found to be promoted by the use of solvents of moderate quality (i.e., toluene) during the film formation process and by higher CP loadings when using solvents of good quality (i.e., chloroform). Finally, WAXS and conductivity measurements demonstrate a strong correlation between the degree of crystallinity of the CP in the π-stacking direction (nanofiber formation) and the electronic conductivity across the bulk of the film. In addition to RRe-P3HT, PS-d 8 blends with semi-crystalline poly­(3-dodecylthiophene) (P3DDT) or poly­(3,3‴-didodecyl­[2,2′:5′,2″:5″,2‴-quaterthiophene]-5,5‴-diyl) (PQT-12) and blends with amorphous regio-random poly­(3-hexylthiophene) (RRa-P3HT) were investigated over concentrations ranging from 0.1 to 50 wt % of CP. This work highlights the importance of understanding the factors that influence the phase morphology in blends of CPs and commodity polymers, as this directly alters charge transport pathways and performance of the organic electronic devices that rely on these materials.

Strategies for the Development of Conjugated Polymer Molecular Dynamics Force Fields Validated with Neutron and X-ray Scattering

“…The differing interactions of X-rays and neutrons can be particularly advantageous during an experiment to highlight structural or dynamic features of interest. In neutron scattering, the large difference in cross section between hydrogen and its isotope deuterium can be used to generate contrast between two phases that may otherwise be difficult to differentiate with microscopy techniques, such as two blended polymer phases demonstrated in our previous work . The technique of tuning the SLD of materials in a complex sample to generate contrast is called contrast variation.…”

Gaining control over conjugated polymer morphology to improve the performance of organic electronics

“…Hence, Wolf et al applied contrast-variation small-angle and ultra-small-angle neutron scattering along with wide-angle X-ray scattering (WAXS) to examine the self-assembly and polymer chain conformation of polythiophene-based CPs in bulk blends with deuterated polystyrene (PS-d8). 77 Firstly, phase-separated blend morphology was found to be dependent on CP concentration, forming larger globular domains with the concentration increase. Secondly, polymer regioregularity was demonstrated to affect the shape of the aggregates: while RR-P3HT blends were found to form both nanofibers and semi-crystalline globular regions, regiorandom RRa-P3HT blend was observed to form amorphous globular phase separated morphology.…”

“…This work underlines the importance of examining the CP blend morphology-charge transport relationships, to choose pertinent processing conditions and improve the device performance. 77…”

“…Hence, Wolf et al applied contrast-variation small-angle and ultra-small-angle neutron scattering along with wide-angle X-ray scattering (WAXS) to examine the selfassembly and polymer chain conformation of polythiophenebased CPs in bulk blends with deuterated polystyrene (PS-d8). 77 Fig. 3 (a) Proposed P3HT nanowire structures with (A) complete or (B) partial defect expulsion, where the darker grey area corresponds to the higher crystallinity region.…”

Multifunctional silver nanowire coated fabric capable of electrothermal, resistance temperature-sensitivity, electromagnetic interference shielding, and strain sensing

“…Smart wearable textiles have attracted widespread attention due to their flexibility, high sensitivity, stretchability, and light weight. Generally, conductive polymers (polyaniline, 1,2 polypyrrole, and 3,4 polythiophene 5,6 ), carbon materials, 7 metal particles 8 and piezoelectric yarns, 9 nanowires, 10 nanotube, 11 PVDF and ZnO nanofibrous composites, 12 photovoltaic energy textile, 13 copper, 14 nonmonotonic piezoresistive fibers, 15 and other nanomaterials can all make textiles conductive. However, conductive polymer as a conductive fill gives a relatively high conductivity, 16 but poor hand feeling and air permeability.…”