Polymerization kinetics in highly viscous media
Polymerization kinetics in highly viscous media
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高粘度介质中的聚合动力学
DOI：
10.1002/pol.1966.150040914
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发表时间：
1966
期刊：
影响因子：
--
通讯作者：
G. Smets
中科院分区：
文献类型：
--
作者：
F. Schrijver;G. Smets
通过向纯单体及其在苯中的溶液中加入不同量的惰性聚苯乙烯，考察了反应介质粘度对苯乙烯聚合速率的影响。偶氮二异丁腈在25℃和70℃下进行光化学（λ = 365 μ）分解；紫外光谱法测定其分解速率。红外光谱（2020cm .−1）测定了二甲基- N -氰异丙基烯丙胺（DKI）的生成速率。用a14标记引发剂，用闪烁法测定了引发效率。用扩张法测定聚合速率。粘度的增加不影响引发剂的分解速率；相反，在光化学分解过程中，DKI浓度增加，效率明显下降（从0.51下降到0.30）。从光聚合速率的角度来看，粘度的增加导致反应的顺序相对于引发剂（从0.5到0.3）降低，相对于单体从1.5到2增加。这些结果是基于两个生长链之间终止速率常数的降低，有利于生长链和初级自由基之间的终止反应。由于溶液粘度的增加，这些对起始反应和终止反应的影响在相反方向上影响聚合速率，并相互补偿约25%。
The influence of the viscosity of the reaction medium on the rate of polymerization of styrene has been examined by adding different amounts of inert polystyrene to pure monomer and its solutions in benzene. Azobisisobutyronitrile was decomposed photochemically (λ = 365 mμ) at 25°C. or thermally at 70°C.; its rate of decomposition was followed by ultraviolet spectrometry. The rate of formation of dimethyl‐N‐cyanoisopropylketenimine (DKI) was followed by infrared spectrometry (2020 cm.−1). The initiation efficiency was determined by the scintillation method with the use of a14Clabeled initiator. The rate of polymerization was followed dilatometrically. An increase of viscosity does not affect the rate of decomposition of the initiator; on the contrary, during the photochemical decomposition, it causes an increase of DKI concentration and an appreciable decrease of efficiency (from 0.51 to 0.30). From the point of view of the rate of photopolymerization, an increase of viscosity causes a decrease in the order of the reaction with respect to the initiator (from 0.5 to 0.3) and an increase with respect to monomer from 1.5 to 2. These results are interpreted on the basis of a decrease of termination rate constant between two growing chains in favor of a termination reaction between a growing chain and a primary radical. These effects, due to an increase of the viscosity of the solution, on the initiation and termination reactions influence the rate of polymerization in opposite direction and compensate each other to approximatively 25%.