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Effects of Polymer Chemistry on the Properties of Polyelectrolyte Complex Coacervates

Huang, Jun (2023) Effects of Polymer Chemistry on the Properties of Polyelectrolyte Complex Coacervates. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Polyelectrolyte complexes (PECs) are prepared via mixing of oppositely charged polymers in aqueous solutions. Because they can exhibit a broad range of material properties under different conditions, they have found use in a number of applications, including as drug carriers and separation membranes for environmental pollutants. While polymer composition should be a critical variable shaping the physical properties of these materials, chemical features of the polymers have to date received significantly less attention than simple solution parameters such as pH and salt concentration. In this thesis, we addressed this knowledge gap by systematically exploring the polymer composition dependence of the properties of complex coacervates. Using post-polymerization functionalization, we first prepared polyelectrolytes varying charge densities and either acrylamide or butyl acrylamide comonomers, and compared their salt responses and viscoelastic properties. This work demonstrated that decreasing charge density reduces the stability of coacervates and speeds their relaxation dynamics. We then prepared a library of polymers containing a wider range of charge densities and nonionic sidechain lengths, and systematically explored the charge density and hydrophobicity dependence of the coacervate phase behavior. From this work, we discovered that the salt response is divided into distinct regimes dominated by either charge density or hydrophobicity. Isothermal titration calorimetry studies revealed that this behavior results from differences in the enthalpic driving force for the complexation interactions, and provide insight into the influence of polymer composition on the thermodynamics of polyelectrolyte complexation. Finally, we investigated the role of cation-pi interactions by incorporating aromatic functionalities into the polymer chains. The dependence of the salt responses and enthalpies of complexation on both the aromatic content and the cation of the salt present in solution observed in this work demonstrate the important role of cation-pi interactions in polyelectrolyte complexation. Together, this work provides valuable insight into the fundamental role of non-ionic functional groups in moderating inter-chain interactions in polyelectrolyte complexes, and suggests that control of polymer composition should be a powerful tool in designing polyelectrolyte complexes and coacervates with targeted properties for practical applications.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Huang, Junjuh68@pitt.edujuh68
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairLaaser,
Committee MemberHorne,
Committee MemberMeyer,
Committee MemberVelankar,
Date: 25 January 2023
Date Type: Publication
Defense Date: 26 August 2022
Approval Date: 25 January 2023
Submission Date: 21 November 2022
Access Restriction: 2 year -- Restrict access to University of Pittsburgh for a period of 2 years.
Number of Pages: 180
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: Polyelectrolyte complexes, coacervates
Date Deposited: 25 Jan 2023 20:08
Last Modified: 25 Jan 2023 20:08


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