Abstract
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.
Original language | English |
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Pages (from-to) | 4333-4340 |
Number of pages | 8 |
Journal | Journal of Physical Chemistry Letters |
Volume | 8 |
Issue number | 18 |
DOIs | |
State | Published - Sep 21 2017 |
Funding
This research was sponsored by the Laboratory Directed Research and Development (LDRD) Program of Oak Ridge National Laboratory. The work was conducted at the Center for Nanophase Materials Sciences and the Spallation Neutron Source, which are U.S. Department of Energy Office of Science User Facilities. S.G. acknowledges support by the National Science Foundation under Grant No. CHE-1565985. The XSEDE allocation TG-DMR110037 and use of the USC HPC cluster funded by the National Science Foundation under Grant No. CHE-1048629 are also acknowledged.