Stabilized polymer microparticles by precipitation with a compressed fluid antisolvent .2. Poly(propylene oxide)- and poly(butylene oxide)-based copolymers
Stabilized polymer microparticles by precipitation with a compressed fluid antisolvent .2. Poly(propylene oxide)- and poly(butylene oxide)-based copolymers
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DOI：
10.1021/la961017r
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发表时间：
1997-03-19
期刊：
影响因子：
3.9
通讯作者：
Johnston, KP
中科院分区：
文献类型：
--
作者：
Mawson, S;Yates, MZ;Johnston, KP
含有聚（环氧丙烷）（PPO）或聚（环氧丁烷）（PBO）稳定剂基团和聚（环氧乙烷）（PEO）锚基团的嵌段共聚物防止无定形聚（甲基丙烯酸甲酯）（PMMA）微粒的絮凝，所述无定形聚（甲基丙烯酸甲酯）微粒通过在23 ℃下将PMMA溶液喷射到流动的液体CO2中而形成。当溶解的PPO-PEO-PPO三嵌段和PBO-PEO二嵌段共聚物与CO2进料流一起引入时，产生0.1-0.5 μ m初级PMMA颗粒。然而，对于相同总量的稳定剂，当这些稳定剂通过聚合物溶液相进料时，形成更大的，在某些情况下更球形的微粒（0.5-2.0 μ m）。稳定剂的有效性描述在其浓度和它如何分配之间的分散相，界面，和CO2相。在许多情况下，在CO2中仅具有中等溶解度的稳定剂比具有较高或较低溶解度的稳定剂更有效。当稳定剂与溶液相一起引入时，它不必可溶于CO2以防止絮凝。通过比浊法原位测量了胶乳的粒径、稳定性、临界絮凝密度和絮凝的可逆性，以了解超临界流体中的空间稳定机制。通过扫描电子显微镜测定的产品中的初级颗粒的尺寸与通过比浊法进行的颗粒尺寸的原位测量一致。
Block copolymers containing either poly(propylene oxide) (PPO) or poly(butylene oxide) (PBO) stabilizer group(s) and a poly(ethylene oxide) (PEO) anchor group prevent flocculation of amorphous poly(methyl methacrylate) (PMMA) microparticles formed by spraying PMMA solutions into flowing liquid CO2 at 23 degrees C. When dissolved PPO-PEO-PPO triblock and PBO-PEO diblock copolymers are introduced with the CO2 feed stream, 0.1-0.5 mu m primary PMMA particles are produced. However, larger, and in some cases more spherical microparticles (0.5-2.0 mu m) are formed when these stabilizers are fed via the polymer solution phase, for the same overall quantity of stabilizer. The effectiveness of the stabilizer is described in terms of its concentration and how it partitions between the dispersed phase, the interface, and the CO2 phase. In many cases stabilizers with only moderate solubilities in CO2 are more effective than those with higher or lower solubilities. When the stabilizer is introduced with the solution phase, it does not have to be soluble in CO2 to prevent flocculation. The latex particle size, stability, critical flocculation density, and reversibility of flocculation have been measured in-situ by turbidimetry to understand the mechanism of steric stabilization in supercritical fluids. The size of the primary particles in the product determined by scanning electron microscopy is consistent with in-situ measurements of particle size by turbidimetry.