Deuteration Effects on Thermal, Crystallization, and Optoelectronic Properties of Donor-Acceptor Conjugated Polymers

Deuteration is a popular method in spectroscopic and scattering techniques such as NMR and neutron scattering to control signal contrast. The abundant hydrogen of the polymers has significant differences in scattering cross section compared to deuterium, which alters scattering length density and promotes contrasts. As contrast fundamentally governs neutron scattering, the deuteration of parts of the polymer allows for understanding the structure and dynamics of a given polymer at a molecular level. However, despite the efforts in the past, there are few works on deuteration influences on electronically active conjugated polymers (CPs). Hence, this work investigated high-performing donor-acceptor (D-A) CPs with deuterated sidechains to study their influences on thermal, crystal ordering, and optoelectronic properties. The polymers, such as polyalkylthiophene (P3ATs) and diketopyrrolopyrrole (DPP) based polymers, were explored. Thermal measurements showed that P3AT had lower melting and crystallization after deuteration, whereas DPP polymers had the opposite trend. However, the morphology and optoelectronic properties had no changes upon deuteration, as confirmed by microscopic and scattering studies and thin-film transistor measurements. Hence, the deuteration studies popular in neutron scattering should be performed carefully, especially for dynamics studies.