Viscometry of polyelectrolyte solutions: Star-like versus linear poly[[2-(methacryloyloxy)ethyl] trimethylammonium iodide] and specific salt effects. (August 2017)

• Record Type: Journal Article
• Authors: Bercea, Maria; Wolf, Bernhard A.
• Is Part Of: European polymer journal. Volume 93(2017)
• Page Start: 148
• Page End: 157
• Publication Date: 2017-08
• Subjects: Polymers -- Periodicals; Polymerization -- Periodicals; Polymères -- Périodiques; Polymérisation -- Périodiques; Polymerization; Polymers; Periodicals; Electronic journals; 547.705
• DOI: 10.1016/j.eurpolymj.2017.05.040
• Languages: English
• ISSNs: 0014-3057

Abstract

Graphical abstract: Degree of coil overlap, Ω, for the star shaped (full lines) and for the linear polyelectrolyte (broken lines) as a function of the reduced polymer concentration in aqueous and 0.1 M salted solutions. Black curves: CaCl2 . Highlights: The intrinsic viscosity of the 3-arm star polymer in water is lower than of corresponding linear chains. Extra salt addition presents a smaller effect for star shape macromolecules. Boltzmann sigmoid models the viscosity from pure water to saturated salted solutions. The chemical nature of the salt influences the viscosity-concentration dependences. Abstract: The intrinsic viscosities, [ η ], of the 3-arm star polyelectrolyte in pure water are for a given molar mass considerably lower than for the linear product because of the higher monomer concentration and charge density in isolated coils. These effects are much more pronounced than in the case of uncharged macromolecules. Extra salt (NaCl, NaI, CaCl2 ) reduces the solution viscosities of the 3-arm star polymer less than of the linear product. The transition of [ η ] from the value in pure water to the minimum saturation value at high salt concentrations follows a Boltzmann sigmoid. In saline solvents the changes of the viscosities with rising polymer concentration depend strongly on the chemical nature of the salt and on the molecular architecture of the solute. The present findings demonstrate the necessity to account for thermodynamic interactions between all components of the mixture, in addition to the usual electrostatic considerations. These considerations should turn out helpful for a better understanding of salt induced topological transitions of charged biopolymers.