用PS-SnCl_4-CH_3COC_2H_5固载引发剂引发异丁基乙烯基醚聚合及其动力学

用PS-SnCl_4-CH_3COC_2H_5固载引发剂引发了异丁基乙烯基醚(IBVE)的聚合反应,研究了诸因素对IBVE聚合反应的影响。结果表明,在大气环境和常温下,IBVE本体聚合的动力学方程为R_p=KI]~(2/3)。对不同的助剂,R_p的递减顺序为CH_2ClCH_2Cl,CCl_4,CHCl_3。聚合反应初期和中期的反应活化能分别为-26.48kJ/mol和45.63kJ/mol。聚合物的(?)_n随反应时间或单体转化率的增加而增大。在适宜的温度下,当固载引发剂用量较少,助剂用量较大时,该反应为易控制的匀速反应。

POLYMERIZATION OF ISOBUTYL VINYL ETHER USING POLYSTYRENE-SUPPORTED PS-SnCl_4-CH_3COC_2H_5 INITIATION SYSTEM AND ITS KINETICS

A polystyrene (PS) -supported Lewis acid initiation system (PS- SnCl4 - CH3COC2H5) was applied for cationic polymerization of isobutyl vinyl ether (IBVE).Investigations were carried out on several aspects concerned with the kinetics of the polymerization process including the quantity of catalyst and additives used . the type of additive selected and temperature effects .The polymerization process initiated by the PS-SnCl4-CH3COC2H5 system was proved having a cationic coordination mechanism . It propagates gradually with time . In the early stage , polymerization rate is controlled by the active centers available on the surface of PS substrate with an activation energy of -2648 kJ/mol . In the mid stage , the polymerization rate is controlled by the diffusion rate of monomers and the viscosity of polymer solution ,with an activation energy of 45.63 kJ/mol .The molecular weight of polymers produced increases with concentration and conversion of monomers (Figure 1). Kinetic studies showed that the rate of polymerization was raised by the addition of more catalyst (Figure 2).The kinetic equation of polymerization is written asRp=KI]2/3.Temperature also has its own effect on polymerization process . In the early stage , the lower the temperature , the faster the polymerization proceeds . In the mid stage , Rp increases with rising of temperature .The type and quantity of additives selected have a signif-icant effect on the capability of active centers to form coordination complexes , and consequently cause changes of the polymerization rate . The polymerization rate of IBVE in different additive media follows the order : CH2ClCH2Cl>CCl4>CHCl3 . Rp exhibits an increase trend when additive is used in a large amount .The experiments showed that ,at an adequate temperature , when the amount of catalyst used is reduced and additive increased ,polymerization of IBVE using spherical PS-SnCl4-CH3COC2H5 catalyst is carried out at a uniform speed with an easy access of control .