Circular Intensity Differential Scattering Reveals the Internal Structure of Polymer Fibrils

Abstract

The optical and electronic properties of π-conjugated polymers in organic electronic devices depend on their intra and inter-chain interactions, dictated by the internal arrangement of the polymer chains in an amorphous or semi-crystalline aggregated state. Here, we discuss the utility of circular intensity differential scattering (CIDS) of circularly polarized light as a sensitive probe to identify the internal arrangement of the polymer chains in helical polymer aggregates. We advance existing theoretical models to utilize the CIDS response and extract structural properties such as the size, orientation and periodicity of a polymer aggregate. As an example, we analyze the CIDS signatures of helically assembled fibrillar aggregates of a chiral polymer poly[(9,9-di-n-octylfluorenyl-2,7-diyl)-alt-(benzothiadiazole)](PFBT) in solution and reveal that PFBT fibrils incorporate at least 5 intertwined polymer chains. We anticipate our approach can be extended more generally to investigate the internal arrangement of supramolecular assemblies of wide range of fibrillar aggregates of π-conjugated polymers.