Hydroxypropyl cellulose as a green polymer for thermo-responsive aqueous foams

Area of Science:

• Polymer Science
• Materials Science
• Physical Chemistry

Background:

• Hydroxypropyl cellulose (HPC) is a temperature-sensitive polymer.
• Responsive materials offer tunable properties for on-demand applications.
• Foam stability is crucial for many industrial processes.

Purpose of the Study:

• To investigate the temperature-dependent behavior of aqueous hydroxypropyl cellulose (HPC) foams.
• To correlate foam properties with the polymer's solution behavior.
• To elucidate the mechanism behind HPC foam's temperature responsiveness.

Main Methods:

• Foam stability analysis (half-life time measurements) at varying temperatures.
• Dynamic light scattering (DLS) to study polymer aggregation.
• Shear rheology and surface tensiometry to characterize bulk and interfacial properties.

Main Results:

• HPC foams showed a moderate decrease in stability with increasing temperature.
• A dramatic, reversible decrease in foam half-life (<120 s) was observed near HPC's lower critical solution temperatures (LCST).
• LCSTs were identified at 43 °C (no salt) and 31 °C (0.7 M NaCl), correlating with polymer aggregation and significant changes in solution viscosity and surface pressure.

Conclusions:

• The lower critical solution temperature (LCST) of HPC dictates its foam's drastic temperature-responsive behavior.
• Changes in solvent viscosity at the LCST are the primary drivers of foam drainage and stability.
• HPC's tunable LCST offers potential for designing advanced responsive foam systems.