The polystyrene oligomers(PS) with M w =1

500～15

000

Mw/Mn≈2 were prepared by free radical oligomerization with α methylstyrene dimer ( α MSD

2

4 diphenyl 4 methyl 1 pentene) as chain transfer agent.The relationship between α MSD and the molecular weight of the oligomers was studied through thermal oligomerization and BPO initiated oligomerization.It is shown that the molecular weight of PS obviously decreases with the increase of [α MSD] but keeps in almost constant when [α MSD] becomes larger than 10% tither in thermal or BPO initiated oligomerization.The molecular weight of PS was determined based on intrinsic viscosity

1H-NMR

13C-NMR and GPC.It is confirmed that there is a active -C=C- terminal unit in PS by 1H and 13C-NMR spectrometries.