Competition Between Phase Separation and Photopolymerization Kinetics During Polymeric Network Development

The competition between phase separation and photopolymerization kinetics during photopolymerization-induced phase separation (photo-PIPS), can easily be studied using a multiscale method to visualize the extent of phase separation and its overall effect on the cured material. Our main characterization method for phase separation detection is a UV transmittance experiment performed using a custom-built UV light transmission apparatus. Real time-Fourier transform infrared spectroscopy and scanning electron microscopy are also used as further characterization methods. In the UV transmittance experiment, rapid reductions in transmittance indicate the onset of phase separation due to light scattering. Ultimately, the transmittance reaches a minimum point, at which phase separation is at a maximum, and then recovers. This recovery could be due to photoinitiator consumption; however, the recovery is too large to rely solely on this theory. Our phase separating resin is irradiated with varying durations of UV light, at which point the light is turned off and only turned back on intermittently to probe the system and obtain a transmittance value. This enables the system to be frozen in various states of phase separation and network development. By probing the system, it is seen if the transmittance recovery still occurs without further photoinitiator consumption. This study aims to verify whether photoinitiator consumption is the sole reasoning behind the transmittance recovery.