Kinetics of polymerization of vinylene carbonate
Kinetics of polymerization of vinylene carbonate
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碳酸亚乙烯酯聚合动力学
DOI：
10.1002/pol.1958.1202911919
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发表时间：
1958
影响因子：
3.4
通讯作者：
K. Hayashi
中科院分区：
文献类型：
--
作者：
G. Smets;K. Hayashi
研究了碳酸亚乙烯酯聚合动力学与引发剂浓度、单体浓度和温度的关系。在丙酮溶液中，反应级数相对于引发剂浓度等于0.5，与单体浓度无关（（M）= 4.15和14.7摩尔/升）;此外，在70 ℃下不存在任何热聚合。在苯甲酸乙酯中相反（（M）= 3.41摩尔/升。在77°C下）相对于引发剂的表观级数为0.77;与Scanlan在乙酸乙烯酯情况下的结果一致。这种行为被解释的基础上的效率因子q，对应于溶剂自由基的分数能够重新启动增长链。在苯甲酸乙酯溶液中，对于碳酸亚乙烯酯和乙酸乙烯酯，该因子q分别等于0.45和0.80。关于单体浓度，在碳酸亚乙酯作为溶剂的存在下，在整个浓度范围内反应级数为1。该溶剂的转移常数可以忽略不计，因为它是在恒定引发剂浓度下测定分子量的结果。在丙酮和苯中，反应的表观级数为1，仅在稀溶液中;在浓溶液中，少量溶剂会导致反应速率大幅下降。这种行为已被解释的基础上的一般动力学方案，其中交叉终止速率常数Φ和链转移常数与溶剂是主导因素。在苯甲酸乙酯中，反应的特征在于部分降解链转移。碳酸亚乙烯酯聚合的总活化能为22.2千卡/升。摩尔，阿耳忒弥斯方程的系数A等于3.0 × 10−9。
The kinetics of polymerization of vinylene carbonate have been studied as a function of the concentration of initiator, the concentration of monomer, and the temperature. In acetone solution, the order of reaction with respect to the concentration of initiator is equal to 0.5, independent of the monomer concentration ((M) = 4.15 and 14.7 mole/l.); moreover any thermal polymerization is absent at 70°C. Contrary in ethylbenzoate ((M) = 3.41 mole/l. at 77°C.) the apparent order with respect to the initiator is 0.77; in agreement with the results of Scanlan in the case of vinylacetate. This behavior is interpreted on the basis of an efficiency factorq, corresponding to the fraction of solvent radicals able to reinitiate a growing chain. In ethylbenzoate solution this factor q is equal to 0.45 and 0.80 for vinylene carbonate and vinylacetate, respectively. With respect to the monomer concentration, the order of the reaction is 1 in the presence of ethylene carbonate as solvent over the total range of concentrations. The transfer constant with this solvent is negligible because it results from molecular weight determinations at constant initiator concentration. In acetone and in benzene the apparent order of reaction is 1, only in dilute solutions; in concentrated solutions small amounts of solvent cause a strong decrease of the rates of reactions. This behavior has been interpreted on the basis of a general kinetic scheme, in which the cross‐termination rate constant Φ and the chain transfer constant with the solvent are the predominant factors. In ethylbenzoate the reaction is characterized by a partial degradative chain transfer. The overall activation energy of the polymerization of vinylene carbonate is 22.2 kcal./mole and the coefficient A of the Arrhenius equation is equal to 3.0 × 10−9.