Photopolymerization kinetics and gelation time of acrylate/liquid crystal syrups were characterized by photo-differential scanning calorimetry (P-DSC) and photo-rheology technology (P-Rheology)
respectively.The effects of chemical structure and composition of acrylate monomers
and photopolymerization temperature on the kinetics of these syrups were discussed on the basis of the correlation between gelation time and temperature
as well as the polymerization rate constant and activation energy which were calculated from the autocatalysis model.Furthermore
the effects of photopolymerization kinetics on the electro-optical properties and phase-separated structure of the polymer dispersed liquid crystals (PDLCs) were studied.The results indicated that the polymerization rate constant increased and the gelation time decreased with increasing the photopolymerization temperature
the monomer reactivity
and the average functionality of monomers.In addition
the photopolymerization activation energy decreases with increasing the reactivity and average functionality of monomers.Meanwhile
the activation energy before gelation is lower than the global one.When the LC content is 50 wt%
the PDLCs show a bicontinuous phase structure at a submicron scale.Also
the gelation time is significantly shortened with increasing the photopolyemerization rate and temperature
leading to smaller LC domains and denser polymer networks in PDLCs.Consequently
the turn-off time is prolonged and the saturation voltage of the PDLCs lowers
whilst their turn-on time and threshold voltage show little variation.