Polyelectrolyte block copolymers as effective stabilizers in emulsion polymerization
Polyelectrolyte block copolymers as effective stabilizers in emulsion polymerization
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DOI：
10.1021/ma9615516
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发表时间：
1997-04
期刊：
影响因子：
5.5
通讯作者：
H. Müller;W. Leube;K. Tauer;S. Förster;M. Antonietti
中科院分区：
文献类型：
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作者：
H. Müller;W. Leube;K. Tauer;S. Förster;M. Antonietti
由氢化聚丁二烯疏水嵌段和部分磺化聚电解质组成的两亲嵌段共聚物是乳液聚合中有效的稳定剂。在较低的嵌段共聚物相对含量(0.4wt%占单体重量的一部分)和无盐条件下，可以得到粒径约为100 nm、固含量为20wt%的均匀稳定的胶乳。这种优化的嵌段共聚体系的高稳定效率使胶乳体系能够在固体薄膜中形成相对较低的残留极性，并提供了独特的静电稳定的新的有趣的模型体系。比较了在高或低离子强度溶液中的聚合和聚苯乙烯磺酸盐嵌段磺化度的变化，结果表明，在聚合过程中，在低离子强度时胶乳的稳定性最好。完全磺化的聚合物体系可能显示出垂直于颗粒表面的分子取向，而50%的磺化物种沿颗粒表面呈现轨迹状构象，这是由剩余的疏水相互作用解释的。由于这种多表面颗粒接触，部分磺化聚合物的应用导致了更有效的稳定。在较高的稳定剂浓度下，可以发现聚集体，这些聚集体可以通过超声波作用或添加低分子表面活性剂溶液来重新分散。
Amphiphilic block copolymers consisting of hydrophobic block of hydrogenated polybutadiene and a partly sulfonated polyelectrolyte block of poly(styrenesulfonate) are effective stabilizers in emulsion polymerization. At low relative amounts of block copolymer (0.4 wt % as a fraction of monomer weight) and salt-free conditions, well-defined and stable latices with particle diameters of ca. 100 nm and solid contents of 20 wt % are obtained. This high stabilization efficiency of optimized block copolymer systems enables the formulation of latex systems with a relatively low remaining polarity in solid films and offers new interesting model systems with exclusively electrosteric stabilization. A comparison of polymerization in high or low ionic strength solution and the variation of the degree of sulfonation of the poly(styrenesulfonate) block shows an optimum stabilization of the latices at low ionic strength during polymerization. Fully sulfonated polymers systems presumably show a molecular orientation perpendicular to the particle surface, whereas 50% sulfonated species take on a traillike conformation along the surface, which is explained by remaining hydrophobic interactions. Due to this multiple surface particle contacts, the application of partly sulfonated polymers leads to more effective stabilization. At higher stabilizer concentrations, aggregates are found, which can be redispersed by ultrasonification or addition of low molecular weight surfactant solution.