Viscosity–temperature relationships for dilute solutions of poly(cyclohexyl methacrylate) in methyl isobutyl ketone

Abstract

Usually, the temperature dependence of the absolute viscosity q can be written as where RTis the thermal energy and Q is the apparent activation energy of viscous flow which is constant over a limited temperature range. The meaning of the preexponential term A is related to a n activation entropy. This expression is of the Arrhenius form and has been called the Guzman-Andrade equation, which was theoretically derived by Eyring.' Thus, the absolute viscosity of a liquid is given by where N a n d h are, respectively, the Avogadro number and the Planck's constant, V is the molar volume of the liquid, and S is the entropy of activation of viscous flow.From eqs.(1) and (2) we obtainMeasurements of absolute viscosities of dilute polymer solutions and their thermal variation are often employed as a way to characterize properties of macromolecules in solution.',2Moore et a1.4-6 have related the A and Q parameters of the Guzman-Andrade equation to the polymer flexibility and thermodynamic properties of polymer-solvent systems.In this article, we have used eq. (1) to study the behavior of the poly(cyclohexy1 methacrylate) (PCHM) in methyl isobutyl ketone on the temperature range 283-313 K. EXPERIMENTALCyclohexyl methacrylate (Fluka purum) was washed three times with sodium hydroxide followed by distilled water; it was dried over anhydrous NazSO, and distilled ( < 25 mm Hg) in pure dried nitrogen.A sample of poly(cyclohexy1 methacrylate) was obtained by radical polymerization using 1,2-azobisisobutyronitrile (Fluka puriss) as initiator in benzene, at 328 K. The polymer obtained was fractionated by solubility in the system pdioxanelmethanol. All fractions were purified by dissolving in benzene and reprecipitation with methanol. They were freeze-dried.All solvents were analytical grade froE Fluka.Number average molecular weights M, and weight average molecular weights z,, were determined by membrane osmometry and laser light scattering, respectively. In Table I, it can be seen the molecular weights and polydispersity index of the five fractions employed in this work. Viscosities of both pure solvent and polymer solutions were measured, at several temperatures (283-313 K), by means of an modified Ubbelohde viscometer. The kinetic energy corrections were less than 0.2%. The bath temperature was regulated to k0.02 K. Intrinsic viscosities were obtained by graphical extrapolation of both q,,/c and In q,/c to zero concentration of polymer.

Temperature Dependence of Protein Solution Viscosity and Protein–Protein Interactions: Insights into the Origins of High-Viscosity Protein Solutions

“…16,20,22 In eq 4, E a,η is the apparent activation energy of viscous flow, while the pre-exponential term (A) is related to an activation entropy. 54 Typical E a,η values range from 25−30 kJ/mol for linear polymers and can be greater than 60 kJ/mol for polymers with long chain branching. 16,19 By taking the natural log of each side of eq 4, a linear relationship between ln η and 1/T can be used to calculate E a,η and ln A as a function of concentration and formulation conditions.…”

“…The effect of temperature on solution viscosity can be modeled using the Andrade-Eyring equation, an empirical Arrhenius-type model. The Andrade-Eyring equation was derived based on the hypothesis that small molecules move by jumping into unoccupied sites or holes. ,, In eq , E a,η is the apparent activation energy of viscous flow, while the pre-exponential term ( A ) is related to an activation entropy . Typical E a,η values range from 25–30 kJ/mol for linear polymers and can be greater than 60 kJ/mol for polymers with long chain branching. , By taking the natural log of each side of eq , a linear relationship between ln η and 1/ T can be used to calculate E a,η and ln A as a function of concentration and formulation conditions.…”

Polymer Conformation near the Critical Point of a Binary Mixture

“…However, if the solvent is a binary mixture, one of the components (presumably the better solvent) may be preferentially adsorbed to the polymer [2]. de Gennes [3] pointed out that such a preferential wetting layer will contribute an indirect attraction among the monomers within the polymer chain, and the indirect attraction will reduce the size of the macromolecule.…”

Tuning the pH‐responsiveness capability of poly(acrylic acid‐co‐itaconic acid)/NaOH hydrogel: Design, swelling, and rust removal evaluation

“…Furthermore, it has shown 18 that water absorbency of hydrogels linearly rises when increasing the initiator concentration while the molecular weight in polymerization by free radicals decreases. It is important to notice that in our work, the concentration range of initiator and crosslinking [19][20][21][22][23][24] selected for the study (0.2-0.4%) did not allow us to observe dramatic changes in the hydrogel swelling after their modification (when maintaining constant the pH:ASS, monomers ratio, and neutralizing percentage). The combined effect of these two parameters on hydrogel swelling behavior is shown in the three-dimensional response surface plots obtained at pH:ASS 4.0, 7.5, and 11.0 ( Figure S3 of Supporting Information).…”