Period-doubling behavior in frontal polymerization of multifunctional acrylates

Area of Science:

• Polymer Chemistry
• Chemical Engineering
• Nonlinear Dynamics

Background:

• Frontal polymerization typically exhibits planar front propagation.
• Nonplanar fronts can display complex dynamics like spin modes and pulsations.
• Understanding these dynamics is crucial for controlling polymerization processes.

Purpose of the Study:

• Investigate the origins of periodic and aperiodic modes in frontal polymerization.
• Explore the influence of diluents on front dynamics.
• Examine the role of cross-linking and activation energy in bifurcation phenomena.

Main Methods:

• Studied frontal polymerization of 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane ethoxylate triacrylate (TMPTA) with Lupersol 231 initiator.
• Used reactant solutions of HDDA with diethyl phthalate (DEP) and TMPTA with dimethyl sulfoxide (DMSO).
• Introduced benzyl acrylate (BzAc) to maintain invariant front temperature for activation energy studies.

Main Results:

• Observed period-doubling behavior leading to chaotic modes and pulsating symmetric modes.
• Demonstrated that diluents significantly influence dynamical behavior, similar to self-propagating high-temperature synthesis (SHS).
• Identified the degree of cross-linking as a bifurcation parameter and observed period-doubling bifurcations via activation energy changes.

Conclusions:

• Diluents can induce rich dynamical behavior in frontal polymerization.
• Frontal polymerization dynamics exhibit complex bifurcations analogous to those in SHS.
• Activation energy is sensitive to polymerization degree and can be a pathway to observe bifurcations.