In this paper, the effects of temperature from 60 ℃ to 80 ℃ and the molar ratios in monomer feed on the copolymerization of α-methylstyrene （AMS） and styrene （St） were studied. The resulting copolymers, designated as PAS, were characterized by FTIR, GPC, NMR and TGA. When the reaction temperature was below 75 ℃, the molecular weights increased almost linearly as the evolution of the copolymerization. The phenomenon revealed that AMS could mediate the conventional free radical polymerization having some features of a controlled system. As the AMS/St = 50/50 （molar） in feed, the overall fraction of the AMS unit incorporated into the copolymer was as high as 42 mol%, the monomer conversion could be more than 90 wt% and the molecular weights could reach as high as 4400. However, since the styrene is more reactive than AMS, the AMS fraction in copolymer increased with the overall monomer conversion. The 13C-NMR revealed the products were random copolymers which had triads, such as -AMS-AMS-AMS-, -St-AMS-AMS- （-AMS-AMS-St-） and -St-AMS-St-. TGA curves demonstrated that the degradation temperature of the resulting copolymers went down from about 356.9 ℃ （0 mol% AMS） to 250.2 ℃ （42 tool% AMS）. This behavior demonstrated that there exist weak bonds in the AMS- containing sequences which could be used as potential free radical generators.
