论文部分内容阅读
用阴离子活性聚合的方法合成了不同分子量的聚苯乙烯大单体。测定了大单体(M_1)-MMA(M_2)在AIBN引发下溶液共聚时的表观竞聚率,发现它们与大单体的分子量无关,但温度对r_(2,app)有很大影响、(r_(1,app)=0.70℃时r_(2,app)=0.32±0.07,75℃时r_(2,app)=0.53±0.13),这一现象与链增长过程中的扩散因素有关。进一步测定了两种单体的共聚速率、表观活化能与共聚物的分子量,测得了末端为甲基丙烯酸申酯的增长链与大单体的交叉增长反应速率。实验发现在较宽的转化率范围内,大单体的共聚速率与其在体系中的浓度无关,我们认为这种反常的动力学行为是由于大单体在溶液中的形态以及大分子链之间相互缔合所致。通过不同的方法测定了同样条件下台成的大单体与聚苯乙烯的分子量,间接证实大单体在稀溶液中以弱的缔合体形式存在。
Polystyrene macromonomers with different molecular weights were synthesized by anionic living polymerization. The apparent reactivity ratios of the macromonomer (M_1) -MMA (M_2) to AIBN-initiated solution copolymerization were determined and found to be independent of the molecular weight of the macromonomer, but the temperature had a significant effect on r_ (2, app) (2, app) = 0.32 ± 0.07 at r_ (1, app) = 0.70 ℃, r_ (2, app) = 0.53 ± 0.13 at 75 ℃). This phenomenon is related to the diffusion factor in the process of chain growth . The copolymerization rate, the apparent activation energy and the molecular weight of the copolymers were further measured. The cross-reaction rate of the growth chain with the macromonomer at the terminal was measured. It has been found that the copolymerization rate of macromonomers has nothing to do with its concentration in the system over a wide range of conversion. We think this abnormal kinetic behavior is due to the morphology of macromonomers in solution and the interaction between macromolecular chains Associated due to each other. The molecular weight of macromonomer and polystyrene under the same conditions was determined by different methods, which indirectly confirmed that the macromonomer exists as weak association in dilute solution.