Monomer Functionality and Polymer Network Formation

In free radical polymerizations multivinyl monomers are used to create cross-linked polymeric materials. By utilizing a kinetic model, the relative effectiveness of divinyl and trivinyl cross-linking agents was investigated in copolymerizations with monovinyl monomers where the cross-linking potential was equivalent. The trivinyl cross-linking agent was found to yield more cross-links and less cycles than the divinyl cross-linking agent. Interestingly, prior to complete reaction, increased cross-linking as a function of conversion is also observed when no cyclization occurs. Here, the trivinyl cross-linking agent produced more elastically active cross-links than the divinyl cross-linking agent as a function of conversion until 100% conversion when the number of cross-links is the same, because cyclization is not present. Differences between divinyl and trivinyl cross-linkers are also observed experimentally in the reaction kinetics of these copolymerizations. With equal cross-linking potential, the trivinyl copolymerization reacted more rapidly than the divinyl copolymerization because the increased cross-linking led to more dramatic autoacceleration.