Modeling the Kinetics of Enhanced Photo-Polymerization under a Collimated and a Reflecting Focused UV Laser

This study explored the kinetics of ultraviolet (UV) laser photoinitiated polymerization in thick polymer systems to achieve improved polymerization efficiency and uniformity. The modeling system comprised an incident UV laser and its reflecting beam, which was focused by a concave mirror to compensate for the exponential decay in the absorbing medium. The polymerization kinetic equation was numerically solved for the initiator concentration. The crossover time was calculated and compared among single beam, two collimated beam and collimated plus reflecting focused-beam systems. For the single beam case, analytic formulas for the time dependent incident beam is derived and demonstrated by measured data. A theoretical crossover time is defined to analyze the measured data based on the dynamic moduli. Lastly, the polymerization boundary dynamics are illustrated, showing the advantage of the combined two beam system. The numerical results provide useful guidance and a novel means for accelerated uniform photo-polymerization, which cannot be achieved by other means.