Author ORCID Identifier

https://orcid.org/0000-0002-6444-9531

Year of Publication

2020

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department

Chemical and Materials Engineering

First Advisor

Dr. Matthew Weisenberger

Second Advisor

Dr. Rodney Andrews

Abstract

Smart electronic textiles cross conventional uses to include functionalities such as light emission, health monitoring, climate control, sensing, storage and conversion of energy, etc. New fibers and yarns that are electrically conductive and mechanically robust are needed as fundamental building blocks for these next generation textiles.

Conjugated polymers are promising candidates in the field of electronic textiles because they are made of earth-abundant, inexpensive elements, have good mechanical properties and flexibility, and can be processed using low-cost large-scale solution processing methods. Currently, the main method to fabricate electrically conductive fibers or yarns from conjugated polymers is the deposition of the conducting polymer onto an inert fiber support by using different techniques. However, the volume occupied by the electrically active coating is generally very small relative to the volume of insulating fiber acting as support. Therefore, when considering the total volume, the bulk electrical conductivity of these coated textiles is usually small, often lower than 10 S/cm, which limits their applications.

An interesting alternate approach would be to fabricate fibers directly from the electrically conductive material avoiding the need for an inert-fiber support. Therefore, in this work, a wet-spinning process for the fabrication of PEDOT:PSS fibers with high electrical conductivity and robust mechanical properties is described. The process includes a coagulating step, a drawing step in a dimethyl sulfoxide bath and two drying steps. The effect that drawing the fibers in the DMSO bath has on the electrical, thermoelectric and mechanical properties of the fibers is studied and correlated to the changes observed in the fibers’ structure. In general, the fibers with the highest state of preferential orientation of crystal planes are also the most conductive and stiffest.

In order to further improve the electrical properties of the fibers, substituting the DMSO drawing step by a sulfuric acid drawing step in the fabrication process is investigated. The sulfuric acid drawn fibers have higher electrical conductivities and better mechanical properties than the DMSO drawn fibers. In fact, electrical conductivities as high as 4039 S/cm and break stresses around 550 MPa are obtained which, to the best of our knowledge, are the highest reported for a PEDOT:PSS fiber. The mechanism by which sulfuric acid enhances the electrical and mechanical properties of the fibers is also investigated. It is found that the sulfuric acid treatment is very efficient removing PSS from the fibers while also promoting substitution of PSS by sulfates as counterions. The removal of PSS and substitution of counterions leads to a reorganization of the crystal structure of the fibers that is more favorable for charge transport.

The last part of this work focuses on the application of the fibers. The mechanical properties of the fibers are compared to traditional textile fibers. Additionally, the time stability of the electrical conductivity of the fibers is also studied. Moreover, the maximum current carrying capacity or ampacity of the fibers is investigated together with some Joule heating-based applications such as thermochromic textiles. A thermoelectric textile device is also demonstrated using the fibers as the p-type legs. Finally, electrochemical applications of the fibers are discussed and demonstrated.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2020.134

Funding Information

Fall 2017 - Spring 2019: DOE EERE Award DE-EE0008095. "Precursor Processing Development for Low Cost, High Strength Carbon Fiber for Composite Overwrapped Pressure Vessels"

Fall 2019 - Spring 2020: NSF Cooperative Agreement No. 18492133. "NSF EPSCoR: RII Track-1: Kentucky Advanced Manufacturing Partnership for Enhanced Robotics and Structures (KAMPERS)"

Share

COinS