Understanding Molecular-Level Interactions Between the Soluplus-Bile Salts Mixed Micellar System

Area of Science:

• Polymer Science
• Colloid and Surface Chemistry
• Materials Science

Background:

• Soluplus, a graft copolymer, exhibits amphiphilic properties suitable for micelle formation.
• Its low cloud point (CP) limits applications in temperature-sensitive formulations.
• Bile salts are biologically relevant surfactants with potential to modify micellar properties.

Purpose of the Study:

• To investigate the micellization behavior of Soluplus in the presence of sodium cholate (NaC) and sodium deoxycholate (NaDC).
• To enhance the cloud point (CP) of Soluplus for broader formulation applications.
• To elucidate the molecular interactions and stability of Soluplus-bile salt mixed micelles.

Main Methods:

• Cloud point (CP) measurements.
• Dynamic Light Scattering (DLS) for micelle size and transitions.
• Small-Angle Neutron Scattering (SANS) for micellar morphology.
• Density Functional Theory (DFT) and Quantum Mechanical (QM) calculations.
• Fourier Transform Infrared (FTIR) spectroscopy.

Main Results:

• NaC and NaDC significantly increase the CP of Soluplus, with NaDC showing a greater effect.
• Mixed micelles exhibit concentration-dependent transitions and defined morphologies.
• DFT and QM analyses reveal weak intermolecular interactions and assess compatibility.
• Soluplus forms micelles with CMC ~7.6 mg/L, hydrodynamic diameter ~70-90 nm.

Conclusions:

• Bile salts effectively enhance the thermal stability of Soluplus micelles.
• Mixed Soluplus-bile salt systems offer tunable properties for advanced formulations.
• The study provides insights into the self-assembly and interactions of amphiphilic copolymers with biological surfactants.