Role of Multivalent Interactions in Dynamic-Template-Directed Assembly of Conjugated Polymers

Abstract

Dynamic-template-directed assembly is a promising method to enhance molecular ordering and electronic properties of solution-coated polymer semiconductor thin films over large area. In this work, we establish that multicomponent dynamic templates of complimentary chemistries can promote polymer crystallization through cooperative multivalent interactions. We investigate this phenomenon using a combination of templating substrates including a fluoropolymer, a hydrogen-bonded liquid and an ionic liquid. Template-dependent multiscale morphology is studied by a comprehensive set of characterization techniques to understand how introducing diverse chemical moieties modulates polymer assembly. Our results clearly confirm synergistic effect between components of complimentary chemistries constituting the dynamic template. The relative degree of crystallinity is improved by 50-150% for films deposited on multicomponent dynamic templates compared to their neat constituents. In addition, macroscopic alignment is increased significantly (2 to 5 times) compared to single-component templates. As a result, highly anisotropic charge transport is observed with apparent hole mobilities up to 3.6 cm2V-1s-1. In contrast, such synergistic effect is not observed when using multicomponent dynamic template of comparable chemistries (i.e. ionic liquid and polymerized ionic liquid). We elucidate the origin of this synergistic effect through a combination of attenuated total reflectance Fourier transform infrared spectroscopy and isothermal titration calorimetry. When the dynamic template is comprised of two or more components interacting with complementary binding sites on the conjugated polymer (esp. backbone vs. side chain), the template-polymer interactions is significantly enhanced compared to the sum of single component contributions. These results provide valuable insights on surface-directed conjugated polymer crystallization during large-area solution coating. Template dynamics is rarely studied, and represents a new opportunity for guiding assembly of soft functional matter.