Synthesis of isotope-substituted conjugated ladder polymers

Abstract

Conjugated ladder polymers (cLPs) represent an intriguing class of macromolecules, characterized by their multi-stranded structure, with continuous fused π-conjugated rings forming the backbone. Isotope substitution, such as deuteration and carbon-13 labeling, offers unique approaches to address the significant challenges associated with elucidating the structure and solution phase dynamics of these polymers. For instance, selective deuteration can highlight parts of the polymer by controlling the scattering length density of specific molecular sections, thereby enhancing the contrast for neutron scattering experiments. In this context, deuteration of side-chains in cLPs represents a promising approach to uncover the elusive polymer physics properties of their backbone. The synthesis of two distinct types of cLPs with perdeuterated side-chains are reported here. During the synthesis, ¹³C isotope labeling was also employed to verify the low levels of defects in the synthesized polymers. Demonstrating these synthetic successes lays the foundation for rigorous characterization of the defects, conformation, and dynamics of cLPs.