Deuteration as a Means to Tune Crystallinity of Conducting Polymers

5 years ago

Deuteration as a Means to Tune Crystallinity of Conducting Polymers

Bobby G. Sumpter, Jacek Jakowski, Jingsong Huang, Sophya Garashchuk, Jong Keum, Kunlun Hong, Yingdong Luo

The effects of deuterium isotope substitution on conjugated polymer chain stacking of poly(3-hexylthiophene) is studied experimentally by X-ray diffraction (XRD) in combination with gel permeation chromatography and theoretically using density functional theory and quantum molecular dynamics. For four P3HT materials with different levels of deuteration (pristine, main-chain deuterated, side-chain deuterated, and fully deuterated), the XRD measurements show that main-chain thiophene deuteration significantly reduces crystallinity, regardless of the side-chain deuteration. The reduction of crystallinity due to the main-chain deuteration is a quantum nuclear effect resulting from a static zero-point vibrational energy combined with a dynamic correlation of the dipole fluctuations. The quantum molecular dynamics simulations confirm the interchain correlation of the proton–proton and deuteron–deuteron motions but not of the proton–deuteron motion. Thus, isotopic purity is an important factor affecting stability and properties of conjugated polymer crystals, which should be considered in the design of electronic and spintronic devices.

Publisher URL: http://dx.doi.org/10.1021/acs.jpclett.7b01803

DOI: 10.1021/acs.jpclett.7b01803