Alargova Rossitza G, Paunov Vesselin N, Velev Orlin D
Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA.
Langmuir. 2006 Jan 17;22(2):765-74. doi: 10.1021/la051825v.
Rodlike polymer particles could have interesting properties and could find many practical applications; however, few methods for the production of such particles are available. We report a systematic study of a droplet shearing process for the formation of polymer rods with micrometer or submicrometer diameter and a length of up to tens of micrometers. The process is based on emulsification of a polymer solution under shear, combined with solvent attrition in the surrounding organic medium. The droplets deform and elongate into cylinders, which solidify when the solvent transfers to the dispersion medium. Stopped flow experiments allow distinguishing all stages of the mechanism. The results are interpreted on the basis of the theory of droplet elongation and breakup under shear. The effects of the viscosity ratio and shear stress are matched against the theoretical expectations. The method is simple, efficient, and scalable, and we demonstrate how it can be controlled and modified. The experimental parameters that allow varying the rod size and aspect ratio include shear rate, medium viscosity, and polymer concentration. Examples of the specific properties of the polymer rods, including self-organization, alignment in external fields and in fluid flows, and stabilization of bubbles, droplets, and capsules, are presented.
棒状聚合物颗粒可能具有有趣的性质，并能找到许多实际应用；然而，制备此类颗粒的方法却很少。我们报告了一项关于液滴剪切过程的系统研究，该过程用于形成直径为微米或亚微米级、长度可达数十微米的聚合物棒。该过程基于在剪切作用下聚合物溶液的乳化，并结合周围有机介质中的溶剂磨损。液滴变形并拉长为圆柱体，当溶剂转移到分散介质中时，圆柱体固化。停流实验有助于区分该机制的所有阶段。基于剪切作用下液滴伸长和破裂的理论对结果进行了解释。将粘度比和剪切应力的影响与理论预期进行了匹配。该方法简单、高效且可扩展，我们展示了如何对其进行控制和改进。允许改变棒尺寸和纵横比的实验参数包括剪切速率、介质粘度和聚合物浓度。还介绍了聚合物棒的具体性质示例，包括自组装、在外部场和流体流中的排列以及气泡、液滴和胶囊的稳定化。
