Ferroelectric Polymers For Organic Electronic Applications

Author : Konstantinos Kallitsis
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (114 download)

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Download or read book Chemical Modification of Fluorinated Electroactive Polymers written by Konstantinos Kallitsis and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic electronics are a low cost alternative to silicon based electronics that nable the fabrication of flexible devices, broadening the scope of electronics beyond the limitations imposed by silicon. For organic electronics to find wider real world applications, three classes of materials have to be optimized. Those classes are conductors, semiconductors and insulators, which are the three building blocks for any electronic device. While organic conductors and semiconductors have attracted significant attention during the past 40 years, research in high dielectric constant and thus high performance insulators is lagging far behind. The class of organic insulating materials with the highest dielectric constant are the Fluorinated Electroactive Polymers (FEPs). FEPs can be categorized in two different groups with vastly different electronic properties. Those groups are the ferroelectrics and the relaxor-ferroelectrics. The ferroelectric polymers, with main representative the copolymer P(VDF-TrFE) find application in electronic devices such as sensors, actuators, non volatile memories and energy generators. On the other hand, relaxorferroelectric polymers, with main representative the P(VDF-TrFE-CTFE) terpolymer are high performance insulating materials and find application in electronics as dielectric layers, in devices such as capacitors, organic field effect transistors, flexible displays and electrocaloric cooling devices amongst others. Although the polymers mentioned above are compatible with a large variety of printing techniques, their limited compatibility with photolithography, which is the method of choice for large throughput electronics production limits their potential of realization. One of the main aims of this thesis was to alter the chemistry of such polymers, in a way that would make them directly compatible with photolithography, while maintaining their desirable electronic properties. To do so, a method allowing the introduction of additional functional groups on FEPs had to be developed. However, due to the excellent chemical stability of fluorinated polymers, developing such a method was a challenging task. The methods developed, use nucleophilic substitution to attach different functional groups on commercially available FEPs by leveraging the existence of groups prone to substitution on the polymer backbone, bypassing the innate chemical stability of such polymers. First, azido groups, known to cross-link upon irradiation with UV light were attached on relaxor ferroelectric P(VDF-TrFE-CTFE) terpolymers. The terpolymers bearing azido groups were directly used as negative photoresists in conventional photolithography process while maintaining a very high dielectric constant. Second, due to safety and stability issues, a more general approach was followed, consisting in grafting type II photoinitiators (based on aryl ketones) on the relaxorferroelectric P(VDF-TrFE-CTFE) and the ferroelectric P(VDF-TrFE) polymers. In those cases exceptionally stable polymers were obtained, with in some cases improved electroactive properties as compared to the pristine materials. These chemistries led us to an extraordinary case study, where FEPs bearing unsaturation were showing remarkable enchancement in electroactive properties. his very simple method of functionalizing FEPS paves the way to many more advances in the field.