Evaluation the thermodynamic behavior of nonionic polyoxyethylene surfactants against temperature changes

Area of Science:

• Physical Chemistry
• Colloid and Surface Chemistry

Background:

• Surfactants are crucial in pharmaceuticals, cosmetics, and industry.
• Micellization, the formation of surfactant aggregates, is key to their functionality.
• Understanding micellization parameters ensures stable pharmaceutical product manufacturing.

Purpose of the Study:

• To investigate the effect of temperature on the Critical Micelle Concentration (CMC) of nonionic surfactants.
• To analyze the thermodynamic parameters of micellization for Polyoxyethylene lauryl ether (C12E23), Polyoxyethylene (10) cetyl ether (C16E10), and Polyoxyethylene (20) cetyl ether (C16E20).

Main Methods:

• Surface tension measurements using the Du Nöuys ring method.
• Determination of CMC from surface tension versus surfactant concentration curves.
• Calculation and analysis of thermodynamic parameters (δG(°)m, ΔH(°)m, ΔS°m) and compensation temperature (Tc).

Main Results:

• CMC initially decreased and then increased with increasing temperature (10-80°C) for all surfactants.
• Surface tension at CMC (γCMC) decreased monotonically with temperature.
• Thermodynamic analysis indicated entropy-driven micellization at lower temperatures, shifting to enthalpy-driven at higher temperatures.

Conclusions:

• Temperature significantly influences surfactant micellization behavior and thermodynamic driving forces.
• The observed CMC trend is attributed to temperature-dependent hydrogen bond formation.
• The study provides critical insights for optimizing surfactant use in pharmaceutical formulations.