Utilizing a Novel Acrylate Chemistry for Application in Controllable Polymer Networks

In this study, a novel chemical reaction which reveals latent acrylates in situ was applied to a multistage network of polymer films. A thiol-ene polymerization forms a low modulus material with epoxides covalently incorporated. A small molecule study confirmed that under heat, the electrophilic carbon in the epoxide ring is susceptible for attack by the nucleophilic thioether group, which produces an acrylate in situ. Upon photoinitiation, these acrylates will react to form a higher modulus material. It was noted in this study that it is effective to use two distinct light stimuli to initiate the polymerization reactions separately, so TPO was used to initiate the thiol-ene reaction using 405nm light and DMPA was used to initiate the acrylate polymerization using 365nm light

Several different monomers can be used to form this multistage network. Vinyl ethers heavily favor the polymerized initial stage of this system than allyl ethers do. Allyl glycidyl ether was used to add epoxides to the system. When a higher ratio of epoxide groups to thiol-ene functional groups was used, there were larger differences in modulus and Tg. However, when there were too many epoxide groups in the mixture of monomers, the gel point would not be reached to form a film because there were not enough crosslinking monomers.