Chloro(5

10

15

20-tetraphenyl-porphyrinato)-aluminum (TPPAlCl) in combination with bis(triphenylphosphine) iminium chloride (PPNCl) was used as binary catalyst for the copolymerization of cyclohexene oxide and CO2. After 9 h reaction at 80℃

poly(1

2-cyclohexylene carbonate) (PCHC) with narrow molecular weight distribution ( Mw / Mn =1.12)was obtained and the yield was as high as 97.2%.However

the number average molecular weight was only 6.8 103. Its found that the concentration and polarity of solvents have little effect on the chain transfer reaction

whereas a decrease in monomer concentration leads to a remarkable reduction in the chain transfer reactions

indicating that there exists obvious chain transfer to monomers.Furthermore

the structure of PCHC was analyzed by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF/MS) technique

upon which the mechanism of chain growth and chain transfer reaction in the polymerization process was proposed:during the copolymerization of cyclohexene oxide and CO2 catalyzed by TPPAlCl/PPNCl system

besides the added initiator

newly active centers were generated by chain transfer

thereby the number of the polymer molecules exceeded the number of the added aluminium porphyrin molecules.Furthermore

the narrow molecular weight distribution of the obtained polymer indicates that the rate of chain exchange is much faster than that of chain propagation.The reversibility of the rapid exchange reaction is the key of alternation of chain termination and chain propagation.