Kinetic behavior of atom transfer radical polymerization of dimethacrylates

The reaction behavior and kinetics of the atom transfer radical polymerization (ATRP) of poly(ethylene I glycol) dimethacrylates (PEGDMA) were studied with respect to polymerization rate, vinyl conversion and the development of a crosslinked network. The polymerization rates were much slower than the corresponding conventional free radical polymerizations with the ATRP systems exhibiting milder autoacceleration. The linear relationship of the semilogarithmic kinetic plot of ln([M-o/[M]) vs. time did not provide good evidence for any living nature of the system because of the combined effects of diffusion controlled radical deactivation and diffusion controlled monomer propagation. The influence of the spacer length (CH2CH2O)(x) between the vinyl moieties of the dimethacrylates on the polymerization kinetics was examined. The polymerization rate and final vinyl conversion increased as value of x decreased from 14 to 9 to 4. These increases in rate and conversion were caused by a more rigid network structure with shorter spacer lengths, and thus more restricted diffusion of the catalyst/ ligand complexes that impeded the radical deactivation. The effect of temperature on the polymerization rate and final vinyl conversion were also investigated.