MODELING THE CONDENSED-PHASE BEHAVIOR OF Π-CONJUGATED POLYMERS

• Main Author: Mask, Walker
• Format: Others
• Published: UKnowledge 2019
• Subjects: Conjugated Polymers; Organic Semiconductors; Computational Chemistry; Molecular Dynamics; Polymer Morphology; Polymer Folding; Materials Chemistry; Organic Chemistry; Polymer Chemistry
• Online Access: https://uknowledge.uky.edu/chemistry_etds/120; https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=1129&context=chemistry_etds

It is well established that the morphology and physical properties of an organic semiconducting (OSC) material regulate its electronic properties. However, structure-function relationships remain difficult to describe in polymer-based OSC, which are of particular interest due to their robust mechanical properties. If relationships among the molecular and bulk levels of structure can be found, they can aid in the design of improved materials. To explore and detail important structure-function relationships in polymer-based OSC, this work employs molecular dynamics (MD) simulations to study various π-conjugated polymers in different environments. Two independent investigations are discussed in this work. One investigation examines how the purposeful disruption of the π-conjugated backbone to increase the chain flexibility impacts the chain structure and packing in the condensed phase. This is done by adding a conjugation break spacer (CBS) unit of one to ten carbons in length into the monomer structure of diketopyrrolopyrrole-based polymers. It is found that trends in the folding and glass structure follow the increase and the parity (odd versus even) of the CBS length. The second investigation analyzes a variety of polymers and small molecule acceptor (SMA) blends to observe the effects of changing the shape of either component and the physical properties of the material, as well as the structure of the polymer chains. It is found that the conjugated core, the side chains, and the planarity or sphericity each influence the density and diffusion of the materials made.