Engineering Cylindrical Polymer Particles: Mechanisms and Fabrication under Mechanical Stress

In our previous study, we reported a facile method for preparing cylindrical polymer particles, namely, the stirring method. In this method, spherical polystyrene (PS) particles were just stirred in a poly(vinylpyrrolidone) aqueous solution using a magnetic stirrer for several hours. This study clarified the formation mechanism of cylindrical shapes from spherical particles by varying the combinations of materials [poly(tetrafluoroethylene) (PTFE) and glass] used in a vial and a bar. The Young's modulus values of PTFE and glass are lower and considerably higher, respectively, than that of PS. Cylindrical PS particles were obtained using a glass vial and a PTFE stirring bar or a PTFE vial and a glass stirring bar. In contrast, no deformation was observed in the spherical PS particles after stirring with a PTFE vial and a stirring bar. Thus, the deformation of the PS particles was attributed to the direct mechanical stress between the vial and stirring bar rather than the shear stress of the fluid. In addition, another fabrication method for cylindrical particles involving the application of direct mechanical stress using two plates, that is, the rubbing process, was developed.