Simulation of Free-radical Polymerization in Microflow Systems

5 Simulation of Free-radical Polymerization in Microflow Systems  

Numerical simulations of styrene free-radical polymerization in micro-flow systems have been reported. The simulations were carried out for three model devices, namely, an interdigital multilamination micromixer, a Superfocus interdigital micromixer, and a simple T-junction. The simulation method used allows the simultaneous solving of partial differential equations resulting from the hydrodynamics, and thermal and mass transfer (convection, diffusion and chemical reaction). 

It is interesting that the simulations indicate that the thermal transfer in such microdevices is high enough to ensure isothermal conditions in spite of the heat released by the polymerization reaction. Moreover, the 

Superfocus interdigital multilamination micromixer can achieve better control than a macrobatch reactor, and the PDI obtained is very close to the theoretical limiting value of 1.5. As the characteristic dimension of the microdevice increases the reactive medium cannot be fully homogenized by diffusion transport before leaving the system, resulting in a high PDI and a loss in control of the polymerization. 

The concept of flash chemistry can be applied to polymer synthesis. Cationic polymerization can be conducted in a highly controlled manner by virtue of the inherent advantage of extremely fast micromixing and fast heat transfer. An excellent level of molecular weight control and molecular-weight distribution control can be attained without deceleration caused by equilibrium between active species and dormant species. The polymerization is complete within a second or so. The microflow system-controlled cationic polymerization seems to be close to ideal living polymerization within a short residence time. 

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