Anomalous polymerization of multifunctional monomers

Monomers containing several double bonds in the molecule follow specific polymerization courses (revealing incomplete conversion of functional groups, shrinkage delayed with respect to equilibrium, monomolecular termination at early polymerization stages, differentiated group reactivity resulting in heterogeneous networks, etc.), different from those shown by the monomers containing one double bond only. A most specific anomaly involves the autoacceleration that appears at the onset of the reaction, and subsequent autodeceleration; therefore, a typical polymerization rate (R(p)) vs. polymerization time (t) relationship first produces a steep maximum (R(p)(max)) past which there is a slow-down until the reaction ceases to proceed. Another anomaly found in this study is a kinetic anomaly observed in the photopolymerization of a series of dimethacrylate monomers. Past the autoacceleration R(p)(max), the R(p) vs. t plot reveals another maximum related in height and position to the operating conditions and to the structure of the reacting monomer (diethylene (DEGDM), triethylene (TEGDM), and tetraethylene (TETGDM) glycol dimethacrylates). The major factors enabling, or facilitating, the other maximum to occur, include the low polymerization rate, a high share of the chain transfer reaction (chain transfer agent present), and an appropriately long spacer between the double bonds in the polymerizing monomer.