Surface Tension, Density and Viscosity Studies on the Associative Behaviour of Oxyethylene-Oxybutylene Diblock Copolymers in Water at Different Temperatures

Abbas Khan, Iram Bibi, Seemab Pervaiz, Khalid Mahmood, Mohammad Siddiq, Mohammad Siddiq

Department of Chemistry, Hazara University, Mansehra, Pakistan.
Department of Chemistry, Quaid-I-Azam University, Islamabad, Pakistan.

DOI: 10.4236/ijoc.2012.21014                

Abstract

The associative properties of methoxy (CH₃O-) ended E₅₈B₁₁ and hydroxyl (-OH) ended E56B19 oxyethylene-oxybuty- lene diblock copolymers in aqueous solution at different temperature are reported in this paper. For both copolymers, E represents an oxyethylene (-[CH₂CH₂O]-) unit and B an oxybutylene (-[CH(C₂H₅)CH₂O]-) unit while the subscripts denote the number average block length. Surface tension measurements were used to find out surface excess concentrations (Γ_m), area per molecule (α^s₁ ) at air/water interface and Gibbs free energy for adsorption (△G⁰_ads ) for the pre-micellar region at four temperatures. Likewise thermodynamic parameters of micellization such as, critical micelle concentrations (CMC), enthalpy of micellization (△H⁰_mic ), standard free energy of micellization (△G⁰_mic) and entropy of micellization (△S⁰_mic ), were also obtained using surface tension measurements. Solution densities were used to deter-mine the partial specific volume of micelle ( V_mic) and micellar density (ρ_mic). Dilute solution viscosities have been used to estimate the intrinsic viscosities [η], solute-solvent interaction parameter (K_H) and hydration value of micelle (W_h) at various temperatures. The effect of temperature on the micelle properties is also discussed.

Keywords

Block Copolymers; Adsorption; Micellization; Surface Tension; Density; Viscosity

Conflicts of Interest

The authors declare no conflicts of interest.

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