Crack propagation and electronic properties of semiconducting polymer and siloxane-urea copolymer blends

Abstract

A persistent challenge in the field of organic electronics is balancing the optoelectronic properties of π-conjugated semiconducting polymers with their thermomechanical properties. A popular and effective approach to resolve this dichotomy is to blend π-conjugated polymers with amorphous, stretchy elastomers. In this work, poly(diketopyrrolopyrrole-co-thienovinylthiophene) was blended with an easily-prepared poly(dimethylsiloxane)-based phenylurea copolymer (PDMS-PU) to further explore this approach. Interestingly, the differing surface energy and polarity of this soft amorphous copolymer in comparison to other common siloxane-based polymers blended with conjugated polymers showed little impact on the solid-state morphology. Various techniques were used to evaluate the properties of the polymer blends, including atomic force microscopy, UV–vis spectroscopy, and x-ray diffraction. An in-depth morphological evaluation was performed on the blend at varying strain, elucidating the formation of cracks at the nanoscale. The results show a significant decrease in crystallinity and increase in crack onset with increased PDMS-PU content. Fabrication of organic field-effect transistors (OFETs) utilizing the new polymer blends exhibited charge mobility up to 8.2 × 10−2 cm2 V−1 s−1, and charge transfer characteristics up to 75 wt.% PDMS-PU content. The study shows the promise of PDMS-PU/conjugated polymer blends for use in OFETs, and towards the large-scale preparation of mechanically robust and stretchable electronic devices.