Summary: The reaction behavior and kinetics of the atom transfer radical polymerization (ATRP) of poly(ethylene 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 semi‐logarithmic kinetic plot of ln([M]0/[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.Apparent rate constants versus vinyl conversions for the ATRP of PEGDMA with the different spacer lengths at 100 °C.magnified imageApparent rate constants versus vinyl conversions for the ATRP of PEGDMA with the different spacer lengths at 100 °C.

Cover: The radical deactivation readily becomes diffusion controlled and causes an acceleration in the atom transfer radical polymerization of poly(ethylene glycol) dimethacrylate. The rate increases with a decrease in the spacer length (CH 2 CH 2 O) x between the vinyl moieties of the dimethacrylate due to a more rigid network structure. Further details can be found in the article on page 287.

With Lewis Acids as catalysts in melt system, the influence of kinds of Lewis Acids, dosages of catalysts on the behaviors of crosslinking and grafting of ethylenepropylene-diene rubber (EPDM) were investigated. The Lewis Acids, such as anhydrous AlCl 3 , FeCl 3 , SnCl 4 , could initiate the crosslinking of EPDM and the grafting between EPDM and polystyrene (PS). The carbon-carbon double bonds existing on EPDM chain were favorable to the formation of the initial carbocation in the presence of Lewis Acids. The carbocation initiated carbonium ion polymerization between the unsaturated bonds, or substituted for a proton from the phenyl in the presence of PS forming EPDM-g-PS copolymer. Anhydrous aluminum chloride was found to be an efficient catalyst and its initiating temperatures for crosslinking or grafting were about 110 C. The amounts of gel and the data of torques showed that there was a competition between the crosslinking-grafting reaction and the degradation of blending components in the presence of AlCl 3 . The EPDM-g-PS copolymer served as a compatibilizer in the EPDM/PS blends and enhanced the mechanical properties.