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首页> 外文期刊>Journal of Colloid and Interface Science >CONTROL OF SURFACTANT LEVEL IN STARVE FED EMULSION POLYMERIZATION .3. LANGMUIR SITE ADSORPTION MODEL FOR COMPETITIVE ADSORPTION OF IN SITU AND ADDED SURFACTANTS IN THE PRESENCE OF ANCHORED GROUPS
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CONTROL OF SURFACTANT LEVEL IN STARVE FED EMULSION POLYMERIZATION .3. LANGMUIR SITE ADSORPTION MODEL FOR COMPETITIVE ADSORPTION OF IN SITU AND ADDED SURFACTANTS IN THE PRESENCE OF ANCHORED GROUPS

机译：饥饿的乳液聚合中表面活性剂含量的控制.3。锚定基团存在时原位和添加表面活性剂竞争性吸附的朗缪尔位点吸附模型

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In emulsion polymerization processes it is important to control the surfactant level to avoid secondary nucleation (too much surfactant) and coagulation (too little). Persulfate initiators generate two types of surface active sulfate-containing species: anchored sulfate groups (10-20%) and mobile in situ surfactant (ISS; 50-70%). This paper examines the significance of the competition between these two species and an added surfactant, sodium dodecylbenzene sulfonate (SDBS). SDBS soap titrations were performed on five uncleaned methyl methacrylate/butyl acrylate latexes with particle sizes from 500 mm to 3.25 mu m at volume fractions from 1 to 30%. Not surprisingly, traditional Langmuir adsorption analyses were unsatisfactory, even after correction for finite volume fraction of solids. We develop a Langmuir site adsorption model to describe the competitive adsorption of ISS and SDBS in the presence of anchored sites and fit the surface tension data from 84 data points to obtain three parameters: the adsorption equilibrium constants for SDBS (K-s = 760 +/- 30 liter mel(-1)) and ISS (K-I = 50 +/- 12 liter mol(-1)) and the limiting area per molecule (APM = 0.37 +/- 0.01 nm(2)). These parameters are quite consistent with literature values determined in noncompetitive situations. The anchored groups were most significant on smaller particles, and the mobile ISS adsorption was most significant on smaller particles at high volume fraction The relatively weak attraction of the ISS to the particle surface is due to its low molecular weight (similar to 400 Da per sulfate group) and results in desorption upon latex dilution. (C) 1995 Academic Press, Inc. [References: 30]
机译：在乳液聚合过程中，重要的是控制表面活性剂的含量，以避免二次成核（表面活性剂过多）和凝结（过少）。过硫酸盐引发剂产生两种类型的含表面活性硫酸盐的物质：固定的硫酸盐基团（10-20％）和可移动的原位表面活性剂（ISS; 50-70％）。本文研究了这两种物质与添加的表面活性剂十二烷基苯磺酸钠（SDBS）之间竞争的重要性。 SDBS皂滴定法是在5种未清洗的甲基丙烯酸甲酯/丙烯酸丁酯胶乳中进行的，乳胶的粒径为500 mm至3.25μm，体积分数为1％至30％。毫不奇怪，即使校正了固体的有限体积分数，传统的Langmuir吸附分析也不令人满意。我们开发了Langmuir位点吸附模型来描述在锚定位点存在下ISS和SDBS的竞争性吸附，并拟合来自84个数据点的表面张力数据以获得三个参数：SDBS的吸附平衡常数（Ks = 760 +/- 30升mel（-1））和ISS（KI = 50 +/- 12升mol（-1））和每个分子的限制面积（APM = 0.37 +/- 0.01 nm（2））。这些参数与在非竞争情况下确定的文献值非常一致。在高体积分数下，固定基团在较小的颗粒上最显着，而流动的ISS吸附在较小的颗粒上最显着。ISS对颗粒表面的相对较弱的吸引力是由于其较低的分子量（类似于每硫酸盐400 Da）组），并导致稀释后解吸。 （C）1995 Academic Press，Inc. [参考：30]

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