The adiabatic calorimetry is a very simple and precise means to measure the rate of polymerization.In this work the method was used to aquire the temperature-time curves of the copolymerization of styrene (St) and methyl methacrylate (MMA) in toluene initiated by 2

2′-azobis (2

4-dimethylvaleronitrile).The sums of crossed chain propagation enthaipy(-Δ H R12 )+(-Δ H R21 )were simulated based on terminal model and penultimate model of Fukuda and Inagaki. The reactor was a 1.5 litre Dewar-reactor equipped with temperature sensors (Pt-100)and a computer

with the system and surrounding temperatures being recorded and calculated on line.At 70—90 ℃ and in the atmosphere of helium

St and MMA were copolymerized and a series of temperature-time curves were obtained by varing the initial concentrations of initiator from 0.02 to 0.03 mol·L -1 with a constant total monomer concentration of 3.5 mol·L -1

and mole concentration ratio of St to MMA ranging from 2/8 to 8/2.The sums of crossed chain propagation enthalpy (-Δ H R12 ) +(-Δ H R21 ) were simulated as 151.03 kJ· mol -1 and 76.57 kJ· mol -1 respectively based on the terminal model and penultimate model of Fukuda and Inagaki. The results show that the value simulated based on the terminal model is coincident with the published datum (136.95 kJ·mol -1 )

but the value simulated according to penultimate model of Fukuda and Inagaki is much less.Besides

the great difference between (-Δ H R12 ) and (-Δ H R21 ) in the penultimate model of Fukuda and Inagaki implies that there remain some problems to be studied further.However

it is still insufficient to prove that the terminal model is better than the penulthmate model of Fukuda and Inagaki for simulating the copolymerization system.