Effects of ultrasonication on the interfacial interactions between poly(3-hexylthiophene) and graphene oxide.

The interactions between poly(3-hexylthiophene) (P3HT) and graphene oxide (GO) have endowed the P3HT/GO composite with excellent properties. Controlling these interactions is important to improve the performance of P3HT-based devices. In this work, ultrasonication was used to regulate the nanostructures of P3HTs (high Mw and low Mw), and further strongly affected the interactions between P3HTs and GO. Atomic force microscopy (AFM), UV-vis absorption spectroscopy, Raman spectroscopy, and grazing incidence X-ray diffraction (GIXRD) were used to study the effects of ultrasonication on the interfacial interactions between P3HTs and GO. With prolonged ultrasonication time, the molecular order of high Mw P3HT nanofibers increased, but that of low Mw P3HT nanofibers decreased. Molecular order is a crucial factor affecting the interfacial interactions between P3HTs and GO, and the amounts of P3HT nanofibers absorbed onto the GO surface increased with the decreased molecular order of the nanofibers. After absorption, the overall molecular order of P3HT/GO composite nanofibers was determined by the nanofibers absorbed onto the GO surface and the nanofibers nucleated by GO. Compared with the molecular order of the nanofibers before absorption, the overall molecular order of the composites with high Mw P3HT increased, but that of composites with low Mw P3HT decreased. These findings can help to understand and modulate the interactions between P3HT nanofibers and GO to provide more information in the field of interfacial engineering of conjugated polymers in polymer-based devices.