UV-Induced Frontal Polymerization of Multifunctional (Meth)acrylates

Photoinduced frontal polymerization was performed on a variety of multifunctional (meth)acrylates, and evaluation of the effect of monomer structure on the ability to sustain a traveling front was made. Photo-DSC was used to measure the photopolymerization rate of each monomer at 25 °C. The results were correlated with their ability to initiate and sustain a traveling front polymerization. The start time and the front velocity of each (meth)acrylate that could initiate/sustain a front photolytically were measured. The results clearly demonstrate that the molecular weight per double bond is directly related to the front velocity. Trimethylolpropane triacrylate (TMPTA), which exhibited the fastest front velocity, was evaluated in depth to determine the effect of varying the photoinitiator and thermal initiator on the frontal polymerization rate. When a multifunctional thiol was added to TMPTA, the start time was dramatically reduced and the velocity increased for low thiol concentrations. However, the velocity decreased when higher concentrations of thiol were added.