Microscopic and Spectroscopic Investigation of Poly(3-hexylthiophene) Interaction with Carbon Nanotubes

Michele Giulianini,John M Bell,Manuela Scarselli,Maurizio De Crescenzi,Paola Castrucci,Nunzio Motta,Eric R Waclawik

doi:10.3390/polym3031433

Abstract

The inclusion of carbon nanotubes in polymer matrix has been proposed to enhance the polymer’s physical and electrical properties. In this study, microscopic and spectroscopic techniques are used to investigate the interaction between poly(3-hexylthiophene) (P3HT) and nanotubes and the reciprocal modification of physical properties. The presence of P3HT-covered nanotubes dispersed in the polymer matrix has been observed by atomic force microscopy and transmission electron microscopy. Then, the modification of P3HT optical properties due to nanotube inclusion has been evidenced with spectroscopic techniques like absorption and Raman spectroscopy. The study is completed with detailed nanoscale analysis by scanning probe techniques. The ordered self assembly of polymer adhering on the nanotube is unveiled by showing an example of helical wrapping of P3HT. Scanning tunneling spectroscopy study provides information on the electronic structure of nanotube-polymer assembly, revealing the charge transfer from P3HT to the nanotube.

Highlights

The discovery of charge conduction in polymers by Bolto et al in 1963 [1] and the synthesis of a conductive polymer by Shirikawa et al in 1977 [2], demonstrated the possibility of employing new organic materials in electronic applications
Due to the limited resolution of the instruments used, the microscopic analysis has been conducted on P3HT/multi-wall carbon nanotubes (MWNTs) compounds
Underneath the film surface, rod-like structures can be individuated and correspond to the MWNTs introduced in the polymer matrix

Summary

Introduction

The discovery of charge conduction in polymers by Bolto et al in 1963 [1] and the synthesis of a conductive polymer by Shirikawa et al in 1977 [2], demonstrated the possibility of employing new organic materials in electronic applications. Conductive polymers or organic semiconductors rapidly conquered several fields of electronic application, being employed since 1990s as active materials for. To further improve organic semiconductor properties, compounds based on the inclusion of carbon nanotubes (CNTs) in the polymer matrix have been proposed, evidencing an enhancement of electrical [11,12] and mechanical properties [13] of the resultant composite. The expectation was to improve electron transport through the percolating network of highly conducting carbon nanotubes in the polymer matrix. In these mixtures, once the photon is absorbed in the polymer, the high electric field at the carbon nanotubes surface is expected to separate the photo-generated carriers. Vacuum conditions (UHV-STM), in order to unveil the self assembled P3HT structure on the nanotube surface and the modification of its electronic and mechanical properties

Composite Preparation

Experimental Techniques

Microscopy Investigation

Spectroscopic Characterisation

Nanoscale Investigation

Conclusion