Tuning Conducting Polymer Crystallinity with Deuteration
Computational model of the 4-chain P3HT [poly(3-hexylthiophene)] system highlighting the hybrid theoretical approach (left). Contours of the actual potential energy for D (red ball) are shown superimposed on the purple grid (middle) along side the 3D isosurface for the corresponding wave function (right). (MM: molecular dynamics; DFT: Density Functional Theory; DVR: Discrete Variable Representation) (hi-res image)
Isotopic substitution (deuteration) is shown to reduce crystal stability in conducting polymers due to zero-point energy and dipole-dipole interactions.
Significance and Impact
Because the crystallinity of polymers effectively tunes their properties, deuteration provides a new way to achieve finer control.
- X-Ray Diffraction measurements determine crystallinity as a function of deuteration.
- Gel permeation chromatography equipped with a triple-detector characterizes polymer chain length.
- Nuclear-quantum effects (zero-point energy) are quantified using first-principles calculations.
- Quantum molecular dynamics calculations show a 30% increase in dynamic polarizability for H versus D.
Jacek Jakowski, Jingsong Huang, Sophya Garashuchuk, Yingdong Luo, Kunlun Hong, Jong Keum, and Bobby G. Sumpter, "Deuteration as a Means to Tune Crystallinity of Conducting Polymers," J. Chem. Phys. Lett. 8, 4333−4340 (2017). DOI: 10.1021/acs.jpclett.7b01803