pure dimer were prepared by GPC from the products of selective dimerization of α-pinene

then with HPLC the number and the relative content ofdimeric isomers in the dimers were measured. And the effect of catalysts and polymerization conditions on the mumber and the relative content of dimeric isomer inthe dimers was investigated. Generally

four peaks of dimeric isomer were observed

but the relative ratio of these peaks changed with the catalysts and reaction conditions. Besides the regular dimers with molecular weight(MW)272

several dimeric isomers with 270 and 274 of a-pinene were observed for the first time by GC-MS combine analysis. On the bases of the datas of the 1H-NMR

13C-NMR

UV and the fragment ions of MS. main molecular structures of these dimeric isomers were proposed.