用绝热量热法研究自由基聚合动力学

该文用Dewar聚合釜研究均相自由基聚合动力学 ,并测定动力学和热力学有关参数 .先用动力学机理已知的甲基丙烯酸甲酯 (MMA)或苯乙烯 (St) / 2 ,2′ 偶氮二 ( 2 ,4 二甲基戊腈 ) (DAVN) /甲苯系统验证绝热量热法的可靠性 ,再用该法研究了动力学机理未知的系统 ,氯化二烯丙基二甲基铵 (DADMAC) / 2 ,2′ 偶氮双(氯化 2 丙基铵 ) /水体系 .用所测动力学和热力学参数计算而得的结果与实验值吻合良好 ,且所测MMA和St的有关参数与文献值也能吻合 .

STUDY ON FREE-RADICAL POLYMERIZATION KINETICS BY ADIABATIC CALORIMETRY

The aqueous solution polymerization of diallyl dimethyl ammonium chloride (DADMAC) with 2,2′ azobis(2 aminopropane) dihydrochloride as initiator was studied by means of adiabatic calorimetry in a well adiabatic 1 5L Dewar reactor equipped with an anchor stirrer.The temperature of the polymerization medium and the surroundings of the reactor was measured by temperature sensors (Pt\|100) and online transmitted to a computer for further data processing.At first, a series of experiments were designed to prove the reliability of adiabatic calorimetry.The homopolymerization of methylmethacrylate(MMA) or styrene(St) initiated by dimethyl 2,2′\|azobis(isobutyrate) in toluene was chosen because the polymerization mechanism of this system has been thoroughly studied and all data are already well known (the reaction order of monomers, MMA or St,was considered as m=1, and the reaction order of AZO initiator used in this study was considered as n=0\^5, its decomposition was a first order reaction without any by reaction, so that p=1,γ=0). At 40～60℃ and in the atmosphere of helium, the monomer was polymerized, and the curves of fluid temperature versus time were obtained online, from which E\-\{ef\}, the overall activation energy of the reaction, can be simulated by the adiabatic calorimeter, then the kinetic and thermodynamic parameters A\-\{ef\} and (-ΔH-R) can be calculated by numerical method with the help of the experimental parameters. The comparison between the simulated values and the published data proved that the method was easy and reliable.Thereafter, the polymerization of DADMAC system was further investigated, a series of temperature versus time curves were experimentally obtained by changing the initial concentrations of monomer(\\-0=2.06～ 2.46mol/L) and the initial temperatures (T\-0=50～60℃). According to the adiabatic calorimetry the kinetic parameters were easily simulated:\%m\%, the order of monomer polymerization was 2 05,and E\-\{ef\} was 108.83 kJ/mol,other parameters A\-\{ef\} and (-ΔH\-R) were obtained in the same way above. The results showed that the calculated values depending on the simulated kinetic and thermodynamic parameters were coincident with the experimental data.