Faithin Omaha eBook Collection

Download or read book EHANCEMENT OF CONJUGATED POLYMER CHARACTERIZATION METHODS; FROM THE INDIVIDUAL CHAIN TO MORPHOLOGICAL FEATURES. written by Ryan Fair and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Conjugated polymers are a subset of polymers which act as electrical semiconductors, enabling the design of electronic devices such as field effect transistors, photovoltaics, and biomedical sensors without the use of inorganic compounds to form the active layer. This subset of semiconductor materials has many unique advantages over their inorganic counterparts: they can be lightweight, solution processable, flexible, stretchable, and biocompatible. However, these distinct properties are not true for all conjugated polymers. Creating devices with the desired properties requires an understanding of the structure-property relationships of these materials. This work will provide novel tools for predicting and characterizing conjugated polymer properties. Doing so will aid the development of design principles for future researchers who wish to customize material properties based on the intended application. First, we will outline methods for accurately characterizing conjugated polymer molecular weight and explore possible sources of error when using gel permeation chromatography. Molecular weight is a critical polymer property which can vary for any given sample. A universal calibration is necessary for obtaining accurate measurements of semiflexible polymers but doing so still does not ensure accurate results. We shall demonstrate the importance of monitoring outlet concentration for molecular weight measurements, which is necessary due to the poorer solubilities of conjugated polymers relative to their flexible synthetic counterparts. Additionally, we will provide discussion of polymer swelling and shrinking effects in solution and how these may influence solution measurement accuracy. Next, we will demonstrate the utility of computational tools for predicting polymer backbone stiffness, or persistence length. This parameter is known to correlate with macroscale device properties, such as mechanical rigidity and electrical conductivity. In this work we will establish the efficacy of a computationally simple tool for predicting persistence lengths of conjugated polymers based on the freely rotating chain model. The predictive model will be compared with measurements from small angle neutron scattering and static light scattering to demonstrate the accuracy of the tool. Finally, we will provide an investigation of novel concepts for electron microscopy of conjugated polymer thin films. We will demonstrate the utility of contemporary techniques for automated acquisition and computational analysis of electron microscopy datasets. This approach will take what is traditionally a qualitative measurement of material morphology and transform it into a quantitative technique. Additionally, we will provide an exploration of some practical limitations of measuring conjugated polymers using electron microscopy, with emphasis on the effects of beam damage at cryogenic conditions. This work will demonstrate an inverse correlation between observed beam damage and probe size at nanoscale probe sizes. Through these works, we will establish characterization methods and predictive models for future researchers who wish to explore structure property relationships of conjugated polymers. Methods will probe properties at scales ranging from the individual polymer chain all the way up to micron-scale morphology. In doing so, we will accelerate the pace of discovery for this exciting class of materials.