Cationic polymerizations of endo-dicyclopentadiene (DCPD) were initiatd by different initiating systems in toluene, n-hexane and methylene chloride and the pollymers (PDCPD) of low molecular weight were obtained. The microstructure of PDCPD was determined by IR and 1H NMR methods. The results show that both norbornenic (NB) and cyclopentenic (CP) double bonds are involved in the polymerization. The propagation on the NB double bond generates structural unit I by direct addition and unit II by carbocation rearrangement, respectively. Similarly, the propagation on the CP double bond produces structural unit III by direct addition and unit IV by transannular rearrangement, respectively. The chain of PDCPD synthesized in toluene and n-hexane consists of all four structural units and shows the content order I

Key words: DICHLOROMETHANE, INFRARED SPECTROPHOTOMETRY, METHYLBENZENE, CYCLOPENTADIENE P, REARRANGEMENT REACTION, PROTON MAGNETIC RESONANCE SPECTROMETRY, POLYMERIZATION, CHAIN STRUCTURE, HEXANE