Due to the conductive nature and great tuning ability from the perspective of material design, conjugated polymers serve as excellent candidates for flexible and large scale electronic devices processing. However, there is still a large room to further improve the performance by engineering and optimizing their nano-scale structure. In this work, the effect of applying electric and acoustic (pressure) fields on conjugated polymers in solutions have been investigated.<br/>It was shown that conjugated polymers can be uni-directionally aligned over nanometer and micrometer scales by an external AC electric field. Optimum amplitude and frequency are identified for alignment by utilizing optical microscopy, small angle neutron scattering (SANS) and atomic force microscopy (AFM). Other affecting parameters, including concentration, solvent quality, and details of the molecular structure of the polymers were systematically studied. It was found by x-ray diffraction (XRD) that, in general, the p-p stacking direction was along the fiber growth axis. The leading alignment mechanism was proposed to be dielectrophoresis occurring during the polymer crystallization process. Both the electrical and mechanical properties were enhanced, as probed by dielectric spectroscopy and rheology.<br/>External application of acoustic waves is yet another powerful way to effectively modify and accelerate the assembly of conjugated polymers into nanowires and sheets. SANS and UV-vis spectroscopy were utilized to explore the conformation of conjugated polymers after ultrasound application in solution. Good solvents, such as chloroform (CF), chlorobenzene (CB), and 1,2-dichlorobenzene (DCB), were used. It has been found that the concentration, sonication time, polymer side chain and backbone units all played a role and affected the polymer structure.<br/>These results demonstrate that external fields are effective mechanisms to direct conjugated polymers into forming desired structures. These approaches also have strong potential to be economically integrated into large scale processing of organic electronics.

Directed structure manipulation of conjugated polymers with external fields

253rd National Meeting (2017)

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