Frontal polymerization in thin layers: Hydrodynamic effects and asymptotic dynamics.

Area of Science:

• Chemical Engineering
• Fluid Dynamics
• Polymer Science

Background:

• Buoyancy-driven convection arises from temperature gradients in thermal frontal polymerization (FP).
• The polymerization reaction front moves perpendicular to the gravity field.
• Reactant viscosity can increase with the degree of polymerization.

Purpose of the Study:

• To theoretically study the dynamics of buoyancy-driven convection in thermal frontal polymerization under adiabatic conditions.
• To investigate the transition between passive and active chemo-hydrodynamic regimes.
• To explain how hydrodynamic currents affect polymerization wave velocity.

Main Methods:

• Theoretical modeling of system dynamics.
• Analysis of reaction-diffusion and hydrodynamic interactions.
• Scaling analysis to explain the influence of convection on front speed.

Main Results:

• The reaction zone propagates as a hot spot with broken symmetry.
• A steady-state asymptotic dynamics is reached, characterized by a propagating front and a surrounding vortex.
• A transition occurs from a passive regime to an active chemo-hydrodynamic regime as vortex strength increases.
• In the active regime, increased convection intensifies and decreases the front speed.
• Increased polymer viscosity shifts flow ahead of the reaction zone, enhancing symmetry.

Conclusions:

• Buoyancy-driven convection significantly alters frontal polymerization dynamics.
• Hydrodynamic effects can lead to a decrease in polymerization wave velocity.
• The study provides insights into the interplay between reaction kinetics and fluid dynamics in FP systems.