Film drainage and interfacial instabilities in polymeric systems with diffuse interfaces.

Area of Science:

• Polymer Science
• Fluid Dynamics
• Surface Science

Background:

• Film drainage is crucial in various industrial processes.
• Understanding the role of interfacial properties is key to controlling fluid behavior.
• Existing models often assume sharp interfaces, neglecting diffusion effects.

Purpose of the Study:

• To experimentally investigate the effect of mutual diffusion in polymeric systems on film drainage.
• To determine the influence of diffuse interfaces on the stability and rate of film drainage.
• To compare experimental findings with current theoretical models.

Main Methods:

• Utilizing material combinations with varying interfacial properties.
• Employing interferometric visualization to observe the thin film between two captive drops.
• Analyzing the dynamics of film formation and drainage at the micrometer scale.

Main Results:

• Highly diffusive systems exhibit non-axisymmetric and unstable film drainage.
• Marangoni convection, driven by diffusion, can either enhance or delay drainage.
• Enhanced drainage was observed to be up to 100 times faster than predicted, while delayed drainage showed agreement with models assuming partially mobile interfaces.

Conclusions:

• Diffuse interfaces in polymeric systems introduce complex dynamics not captured by current models.
• Marangoni convection plays a significant role in modulating film drainage rates.
• This research highlights the importance of considering interfacial diffusion in fluid dynamics studies.