Kinetics of alternating copolymerization of carbon monoxide with styrene or p-ethylstyrene

Alternating copolymerization of carbon monoxide (CO) with styrene (ST) or p-ethylstyrene (EST), catalyzed by the transition metal Pd (II) complexes, was carried out. The kinetics of alternating copolymerization of ST and EST with CO was investigated. The results show that the copolymerization temperature has a sensitive effect on the copolymerization rate and the catalytic activity in the ST and CO copolymerization system. The copolymerization rate increases with the increase of reaction temperature from 55 to 67 degrees C, and then decreases with further increasing the reaction temperature up to 70 degrees C. The variation of the copolymerization rate with the initial CO pressure were also studied, and the results indicate that initial copolymerization rate increases with decreasing the CO pressure in gas phase. Moreover, the semi-continuous experiments performed at different reaction conditions further confirm that lower CO pressure benefits the copolymerization rate. The structure of EST/CO copolymer was verified by means of Fourier transform infrared (FTIR), elemental analysis (EA), H-1 NMR, and C-13 NMR methods. The characteristic results indicate that the EST/CO copolymer prepared from p-ethylstyrene and carbon monoxide in the presence of palladium (II)/2,2'-bipyridyl catalyst is an alternating copolymer. It is interesting to note that there is a higher initial copolymerization rate under proper lower CO pressure in the EST/CO system, which is similar to that in the ST/CO system. In addition, comparing with two systems, there are higher catalytic activity and shorter catalytic life in the EST/CO system than those in the ST/CO system. The different copolymerization rates between EST/CO and ST/CO systems are attributed to the different nature of alpha-olefins.