Robust Aggregations Formed in Conjugated Ladder Polymers Solution Due to Rigid Backbone and Low Dissolve Entropy

Conjugated polymers have been widely investigated where the conjugated ladder polymers (cLPs) get more attention due to its rigid planar backbone and extraordinary electronical properties. However, the polymer chain conformation is less concerned due to its low solubility. Here we investigated the solution properties of carbazole-type cLP and non-ladder control polymer by light scattering, neutron scattering and UV-Vis absorption combined with theoretical simulation. We found that LP solution contains amorphous polymer aggregates that are robust and temperature insensitive. By using Brownian dynamics simulation, we revealed that during solution process the entropy change of cLP is significantly smaller than that of non-ladder control polymer as a consequence of much rigid double-stranded backbone. These results suggest that improving the solubility of the ladder conjugated polymers is necessary for solution processing, like incorporating dense bulky sidechains. This systematic work is beneficial to the design and application of next generation of high-performance devices with conjugated ladder polymers.