Improved Hierarchical Ordering in Supramolecules via Symmetrically Bifunctionalized Organic Semiconductor

Abstract

Block copolymer (BCP)-based supramolecular systems provide a versatile approach to manipulate functional structures spanning several nanometers to macroscopic length scales. Most studies to date focused on supramolecules containing asymmetrically end-functionalized small molecules, and it remains challenging to obtain molecular control over small molecule ordering within the BCP microdomain. Here we designed symmetrically end-functionalized bis-phenol quarterthiophene (BP4T) small molecules and systematically investigated how the end-group chemistry of the small molecules affects the supramolecular assembly process and the resulting morphology. Bifunctionalized small molecules can bridge two adjacent polymer blocks and lead to macroscopically aligned hierarchical assemblies at much higher degree of ordering than previously observed for asymmetrically functionalized small molecule analogues. The supramolecular morphology is very sensitive to the stoichiometry between the BP4T and polymer repeat unit because of the specific molecular organization within BCP microdomain. Furthermore, similar thermoresponsiveness of supramolecule, i.e., ∼40% change in the supramolecular periodicity during the heating and cooling cycles, can be obtained at BP4T loading stoichiometry of 0.5, much smaller than that of asymmetrically functionalized small molecule. These results clearly demonstrate that supramolecular assemblies can be readily manipulated by engineering the small molecule chemistry. Present studies provide basic design principles and an effective route to fabricate well-defined hierarchical assemblies for functional and stimuli-responsive nanomaterials.