Making Light of Shadow Cure: Using Central Composite Design to Predict Cationic Active Center Mobility

The mobility of long-lived active centers in cationic ring-opening photopolymerization facilitates polymer formation in areas never exposed to light (shadow cure); however, current understanding of active center mobility is limited. Using a central composite design of experiments, four key experimental parameters (effective irradiance, sample depth, exposure area, and exposure time) were explored to predict movement of these active centers in a commercially available epoxide by measuring shadow cure length, polymer mass, and apparent conversion. Shadow cure length was found to be the best predictive measure, and additional experiments are underway to refine the accuracy of the model.