Decoupling conjugated polymer’s backbone and sidechain conformation by selective deuteration and neutron scattering*

Conjugated polymers (CPs) with high optoelectronic performance are of paramount interest to industrial applications. Specifically, experimental characterization of conjugated polymer backbone conformations remains underexplored due to limited techniques that can distinguish the backbone and sidechain structures. Thus, relating the electronically functional backbone conformation to the material’s macroscopic optoelectronic property is an ongoing challenge. Here, small-angle neutron scattering techniques (SANS) with contrast variation (CV) experiments are employed on CPs (poly(3-alkylthiophenes) (P3ATs) and diketopyrrolopyrrole (DPP) based polymers). We obtained the form factor of P3ATs’ backbone, sidechains, and cross scattering term by deconvoluting their respective scattering signals. The strong scattering signal from long and flexible alkyl sidechains leads to a seemingly more rigid conjugated polymer. This work offers a methodology to decouple the scattering contribution from the CPs’ backbone and sidechains, thus elucidating the inherent conformation of the electronically active conjugated backbone.