Controlling the shapes and internal complexity of the polymeric particles using liquid crystal-templates confined into microwells

Abstract

Formation and positioning of the topological defects within liquid crystalline (LC) medium confined into microwells were shown to critically effect the shapes and symmetry of the particles obtained after polymerization. Water-soluble, sacrificial poly(vinyl alcohol) microwells with different sizes and shapes were filled with a nematic solution of reactive (RM257) and non-reactive mesogens (5CB) and photopolymerized under ultraviolet light. The characterization of the LC director profile and defect locations were done using a polarized optical microscope. We found that the positions of the defects could be controlled by the elasticity and surface anchoring by tuning the size and the shape of the microwells. Polymerization followed by the extraction of the unreacted part and drying, the particles maintained their final shapes where we observed a critical dependence on the location and charge of the defects. Beyond the three-dimensional shapes, SEM imaging of the particle surfaces revealed that the LC director profile around the defects of different charges to be reflected in the surface morphology. Overall, the outcomes of this study provide a method for the synthesis of three-dimensional polymeric microparticles in different size and shape with predetermined internal structures. The findings herein may be used in different applications such as drug delivery, sensors, soft-robotics.