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P. K. Singh ¹, J. C. Ahluwalia ¹

Affiliations
1 Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi-110 016, IN

Abstract

For surfactants SDDS, HTAB, HPB.H₂O and HPC.H₂O the thermo chemical parameters (̅H₂-H⁰₂) and heat capacities (̅C_p2-C⁰_p2) relative to the pure state, in the pre c.m.c. region at infinite dilution in the monomeric state and at concentrations a little above the c.m.c. for the micellar state have been determined. From these, the enthalpies (ΔH_m) and heat capacities (ΔC_pm) of micellization have been calculated. Results indicate significant hydration of alkyl parts in the micellar state.

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Rameshwarjha ¹, J. C. Ahluwalia ¹

Affiliations
1 Department of Chemistry, Indian Institute of Technology, Hauz Khas, New Delhi 110016, IN

Abstract

The enthalpies of solution (̅H₂-H⁰₂) of some nonionic surfactants polyoxyethylene alkyl ethers (C₁₀E₄C₁₀E₅, C₁₀E₆, C₁₀E₈, C₁₂E₈) and Triton X-100, in water have been measured calorimetrically in pre-CMC and post-CMC regions in the temperature range 283.15 to 328.15 K. From the enthalpies of solution data have been derived the enthalpy of micellization, ΔH_m, the heat capacities of monomeric ΔC_Pmono and micellar forms ΔC_Pmic as well as the heat capacities of micellization ΔC_Pm. The effect of temperature and size of the polar head and non-polar groups of the surfactants has been discussed in terms of the contributions of hydrophobic, hydrophilic and hydrogen bonding interactions. The ΔC_Pm values indicate that there is an appreciable water penetration into the micellar core.

Keywords

Thermodynamics, Micellization, Enthalpy, Heat Capacity, Surfactants, Polyoxyethylene Alkyl Ethers.

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