Link to the University of Pittsburgh Homepage
Link to the University Library System Homepage Link to the Contact Us Form

Design of High-Capacitance Polymers: Side Chain Length and Polarity Effects on Permittivity

Schmidt, Anneliese (2024) Design of High-Capacitance Polymers: Side Chain Length and Polarity Effects on Permittivity. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

This is the latest version of this item.

Primary Text

Download (13MB) | Preview


Dielectric polymers (DPs) are attracting attention for applications in energy storage devices and potential as greener materials. This work serves to expand and explore a variation of side chain (SC) DPs, which addresses one major challenge, inherently low permittivity. This design of SCDPs combines a long aliphatic backbone, having low permittivity and loss, with conjugated SCs, having high permittivity and loss, and is expected to demonstrate these characteristics. Cast films, subjected to a dipole-aligning external field, achieved high permittivities. Effective dipole orientation, facilitated by backbone flexibility and SC conjugation for electron mobility, increased the induced dipole.
A series of polymers with an alkyl backbone and variable length phenylene ethynylene (PhE) SCs were prepared. Diolefin macromonomers, containing a halogenated phenyl, were polymerized via ADMET. Sonogashira coupling of PhE units gave SCs that were 1, 2, and 3 units long, and post-polymerization coupling gave polymers termed: poly-dimer, with two phenyls; poly-trimer, with three phenyls; poly-tetramer, with four phenyls. PhE units were of 2 types: a 2,5-alkoxy functionalized phenyl, for improved solubility, and a 4-nitrile functionalized phenyl, to enhance polarity.
The effects of conjugation length, polarity, and poling the polymers’ permittivities were studied. Sample films, prepared by solution deposition between brass electrodes, were characterized by broadband dielectric spectroscopy at 20 °C and 1 kHz. The type of solvent used showed little effect, whereas the amount of solvent present changed the materials’ response significantly. All unpoled polymers exhibited high permittivities: backbone and poly-tetramer ~4.3; poly-dimer ~4.6; poly-trimer ~4.9. Poling at a 15-volt potential increased their permittivities: backbone ~4.9; poly-dimer ~12.4; poly-trimer ~7.1; poly-tetramer ~5.9. This increase over the unpoled samples demonstrated their potential as high-performance DPs. After poling, the backbone’s small increase, Δε'=0.6, was expected. Surprisingly, as the SC length increased, the Δε' decreased, showing a maximum of: poly-dimer Δε'=7.8; poly-trimer Δε'=2.2; poly-tetramer Δε'=1.6. Alignment of increasingly longer SCs was expected to yield incrementally higher permittivities. One explanation, since permittivities were highly dependent on mobility, longer SCs may remain partially hindered to rotation, despite plasticization. The correlation between SC length and poled permittivity indicates hinderance may increase with SC length and prevent maximum alignment.


Social Networking:
Share |


Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Schmidt, AnnelieseAnneliese.Schmidt@pitt.eduans290
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee CoChairMeyer,
Committee CoChairHutchison, Geoffreygeoffh@pitt.eduGEOFFH0000-0002-1757-1980
Committee MemberLiu, Pengpengliu@pitt.edupengliu
Committee MemberNoonan," <
Date: 8 May 2024
Date Type: Publication
Defense Date: 8 December 2023
Approval Date: 8 May 2024
Submission Date: 5 January 2024
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 211
Institution: University of Pittsburgh
Schools and Programs: Dietrich School of Arts and Sciences > Chemistry
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: dielectric polymers broadband dielectric spectroscopy
Date Deposited: 08 May 2024 17:42
Last Modified: 08 May 2024 17:42

Available Versions of this Item

  • Design of High-Capacitance Polymers: Side Chain Length and Polarity Effects on Permittivity. (deposited 08 May 2024 17:42) [Currently Displayed]


Monthly Views for the past 3 years

Plum Analytics

Actions (login required)

View Item View Item