Semicontinuous Monomer-Starved Emulsion Polymerization as a Means to Produce Nanolatexes: Analysis of Nucleation Stage
Semicontinuous Monomer-Starved Emulsion Polymerization as a Means to Produce Nanolatexes: Analysis of Nucleation Stage
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DOI：
10.1021/la4000654
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发表时间：
2013-05-14
期刊：
影响因子：
3.9
通讯作者：
Sajjadi, Shahriar
中科院分区：
文献类型：
--
作者：
Chen, Yan;Jahanzad, Fatemeh;Sajjadi, Shahriar
在本研究中，通过对成核结束的密切监测，在单体饥饿的苯乙烯连续（微）乳液聚合中，颗粒成核与颗粒生长解耦。这使我们能够排除颗粒生长对成核的影响，因此解开在这个过程中的成核的固有特征。获得了平均粒径小至15 nm的纳米胶乳。成核结束时粒子的平均尺寸几乎与表面活性剂浓度（[S]）无关，而与单体加入速率（R-a）的1/3次方有关。成核时间几乎与[S]（1.0）成正比。在所用的最低单体进料速率下获得最尖锐的粒度分布。所生产的聚合物的重均分子量（（M）/bar（w））随着R-a的降低而降低。开发了一个简单的相关性，其表明数均分子量（（M）除以bar（n））与R-a（1.0）成比例。但与[S]无关（即，[S]（0.0）），这是在公平的协议与实验结果。还表明聚合物分子量与颗粒的平均体积成比例;颗粒越小，分子量越低。
In this research, particle nucleation was decoupled from particle growth in the monomer-starved semicontinuous (micro)emulsion polymerization of styrene by close monitoring of the end of nucleation. This enabled us to exclude the effects of particle growth on nucleation and therefore unravel inherent features of nucleation in this process. Nanolatexes with average particle sizes as small as 15 run were obtained. The average size of particles at the end of nucleation was found to be almost independent of surfactant concentration ([S]) but varied with the rate of monomer addition (R-a) to the 1/3 power. Nucleation time varied almost proportionally with [S](1.0). The sharpest particle size distribution was obtained at the lowest monomer feed rate used. The weight-average molecular weights ((M) over bar (w)) of the polymer produced decreased with decreasing R-a. A simple correlation was developed which shows that the number-average molecular weight ((M) over bar (n)) is proportional to R-a(1.0). but independent of [S] (i.e., [S](0.0)), which was in fair agreement with the experimental results. It is also shown that the polymer molecular weight is proportional to the average volume of particles; the smaller the particle, the lower the molecular weight.