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Phase Behavior of Oppositely Charged Strong and Weak Polyelectrolytes, and Properties of Corresponding Complexes

Zhou, Yi
http://rave.ohiolink.edu/etdc/view?acc_num=akron1555517232053683

Abstract Details

2019, Master of Science in Polymer Engineering, University of Akron, Polymer Engineering.
Complex coacervation and precipitation are two different types of phase separation in a polyelectrolyte complex system composed of two oppositely charged polyelectrolytes. Complex coacervate and precipitate refer to a dense soluble and insoluble polymer-rich phase respectively. Many experimental studies have investigated the effect of solution and environmental conditions on the formation of polyelectrolyte complexes (PECs), including pH values, the added salts and temperature, etc. The formation of PECs is believed to be entropically driven, resulting from the release of small counter ions from the polymer backbone chains. The addition of salts is expected to influence the ionic strength of the polyelectrolyte system, which further influences the complexation process and the physicochemical properties of the complexes, including phase boundaries of coacervation and precipitation, hydrophobicity and water content within complexes. To better understand the polyelectrolyte complexation process and the difference between strong polyelectrolyte vs. weak polyelectrolyte complexation, phase behavior of polyelectrolyte complex systems containing oppositely charged polyelectrolytes, including poly(diallyldimethylammonium chloride) (PDAC), poly(sodium 4-styrene sulfonate) (SPS), poly(allylamine hydrochloride) (PAH), poly (acrylic acid) (PAA), poly(methacrylic acid) (PMAA) were investigated in the presence of four different salts (KCl, KNO3, KBr, KI) based on Hofmeister series to study the effect of salts on water content of different salt-added PEC systems. The additional methyl groups on PMAA backbones can offer a structural difference between PMAA-PAH and PAA-PAH complex systems. In addition, the hydrophobicity and water content of the salt-free or salt-added complexes on the phase boundaries were also studied to help us conversely understand phase behavior. Turbidity was carried out to qualitatively show the phase boundaries of coacervation and precipitation and the effect of added salts on the phase behavior of PECs, providing information of phase behavior changing with different salt-added complex systems. From phase diagrams, two opposite effects of added salts on phase behavior were observed. Thermal gravimetric analysis (TGA) was employed to study the water content of PECs and water content results indicated dual effects of salt on water content of PECs. UV-vis spectroscopy was used to verify the sequestration of ANS into the complexes. Fluorescence spectroscopy was utilized to measure the relative hydrophobicity within the complex coacervate and precipitate on the phase boundaries respectively, using ANS as a probe. The hydrophobicity date was observed to be consistent with water content data and offered some possible explanations for higher water content of PMAA-PAH systems. Modulated Differential Scanning Calorimetry (MDSC) was used to determine the glass transition temperature of complexes, indicating PAA-PAH is softer and added KCl will significantly increase the Tg values while barely change that of PMAA-PAH. Dissolving experiments were taken to study the stability of ionic bonds between oppositely charged polymer chains, showing PAA-PAH complexes are more easily broken by added salts. NMR and FTIR were used to quantitatively determine the intrinsic ion pairs for PAA-PAH and PMAA-PAH complex systems. The intrinsic ion pair density indicated a denser PAA-PAH pairs in the complex system than that of PMAA-PAH which explains the higher water content for PMAA-PAH.
Nicole Zacharia (Advisor)
Kevin Cavicchi (Committee Member)
Bryan Vogt (Committee Member)
Yu Zhu (Committee Member)
69 p.
Polymers
Strong polyelectrolytes; weak polyelectrolytes; polyelectrolyte complexes; phase behavior; water content; hydrophobicity

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Citations

  • Zhou, Y. (2019). Phase Behavior of Oppositely Charged Strong and Weak Polyelectrolytes, and Properties of Corresponding Complexes [Master's thesis, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555517232053683

    APA Style (7th edition)

  • Zhou, Yi. Phase Behavior of Oppositely Charged Strong and Weak Polyelectrolytes, and Properties of Corresponding Complexes. 2019. University of Akron, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron1555517232053683.

    MLA Style (8th edition)

  • Zhou, Yi. "Phase Behavior of Oppositely Charged Strong and Weak Polyelectrolytes, and Properties of Corresponding Complexes." Master's thesis, University of Akron, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555517232053683

    Chicago Manual of Style (17th edition)

akron1555517232053683
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This open access ETD is published by University of Akron and OhioLINK.