The effect of confinement on thermal frontal polymerization†

In thermal frontal polymerization, the interplay between heat diffusion and Arrhenius type reaction kinetics gives rise to a propagating reactive front that is effectively sustained through a system positive feedback mechanism. We seek to understand how spatial confinement affects the system dynamics and overall polymerization kinetics. We find that with increasing confinement of the system, the front propagation velocity decreases and the nearly ‘‘parabolic’’ front profile flattens out. While in bulk or unconfined systems the convective heat and mass transfer effects are responsible for higher heat generation rates and higher temperature gradients, leading to faster front propagation, the convection is significantly suppressed in highly confined systems. Consequently, a smaller number of radicals are generated, resulting in a slower propagation step and long polymer chains.