Trade-off of mechanical and electrical properties in stretchable P3HT/PDMS blending films driven by interpenetrating double networks formation

The balance of electrical and mechanical properties of conjugated polymers is extremely significant toward extending applications in wearable and implantable devices. Blending conjugated polymers with organic elastomers is a straightforward and facile way to improve the deformability of the materials. In this work, poly(3-hexylthiophene) (P3HT) nanowires were blended with a polydimethylsiloxane (PDMS) elastomer via spin-coating on two kinds of substrates, SiO2/Si and PDMS. Organic field-effect transistors based on P3HT/PDMS blending films were tested to evaluate the electronic properties of the films. The phase separation structures, surface morphologies, and the deformation under stretching were characterized by x-ray photoelectron spectroscopy, atomic force microscopy, and optical microscopy, respectively. A stratified structure with P3HT nanowires condensed at the interface formed on SiO2/Si, while an interpenetrating double networks structure yielded on the PDMS substrate. The double networks structure affords P3HT/PDMS blending films not only similar field-effect mobility in a wide range of P3HT content (≥5 wt. %) but also much enhanced stretching performance with respect to the net P3HT film. This double networks structure induced by polarity selection of the substrate might provide an efficient route to prepare flexible blending films with balanced mechanical and electrical behaviors.