MECHANISM AND KINETICS OF THE PERSULFATE-INITIATED POLYMERIZATION OF ACRYLAMIDE
MECHANISM AND KINETICS OF THE PERSULFATE-INITIATED POLYMERIZATION OF ACRYLAMIDE
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DOI：
10.1021/ma00009a004
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发表时间：
1991-04-29
期刊：
影响因子：
5.5
通讯作者：
HUNKELER, D
中科院分区：
文献类型：
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作者：
HUNKELER, D
丙烯酰胺在高单体浓度（25-50重量%）下在40 - 60 ° C的温度下用过硫酸钾作为引发剂聚合。 聚合反应的速率被认为是成比例的单体浓度的5/4次方，广泛报道的依赖性在低和中等水平，这表明该速率顺序是不变的丙烯酰胺浓度高达其在水中的溶解度极限。 还观察到有限的转化率，并且与初始单体浓度无关。 高速率顺序和限制转化率被认为是同一现象的表现：单体增强过硫酸钾的分解。 一个“混合笼复合物”的机制，其中单体和引发剂之间的氢键导致的协会，已经得到。 这假定单体-引发剂缔合导致酰胺和过硫酸盐之间的供体-受体相互作用。 这种电荷转移复合物的分解导致二次引发反应，该反应与过氧化物的热键断裂竞争并且通常优先于过氧化物的热键断裂进行。 它将被证明给聚合速率顺序，单体和引发剂的消耗，和分子量的良好的定量预测。 此外，该机制避免了自由能不一致的特点，现有的理论和推广到其他非离子和离子型丙烯酸类水溶性单体在极性溶剂中。
Acrylamide was polymerized at high monomer concentrations (25-50 wt %) at temperatures between 40 and 60-degrees-C with potassium persulfate as the initiator. The rate of polymerization was found to be proportional to the monomer concentration to the 5/4th power, a dependence extensively reported at low and moderate levels, suggesting that the rate order is invariant to the acrylamide concentration up to its solubility limit in water. Limiting conversions have also been observed and are reciprocally related to the initial monomer concentration. Both the high rate orders and limiting conversion are found to be manifestations of the same phenomena: the monomer-enhanced decomposition of potassium persulfate. A "hybrid cage-complex" mechanism, in which hydrogen bonding between the monomer and initiator lead to association, has been derived. This postulates that the monomer-initiator associate leads to donor-acceptor interactions between the amide and the persulfate. The decomposition of this charge-transfer complex leads to a secondary initiation reaction, which proceeds in competition with and often in preference to the thermal bond rupture of the peroxide. It will be shown to give good quantitative prediction of the polymerization rate order, monomer and initiator consumption, and molecular weight. Furthermore, the mechanism avoids the free-energy inconsistencies characteristic of prior theories and is generalizable to other nonionic and ionogenic acrylic water-soluble monomers in polar solvents.