This study demonstrates the possibility of controlling the directed self-assembly of microsized Janus cylinders by changing the solvent polarity of the assembly media. Experimental results are analyzed and theoretical calculations of the free energy of adhesion (ΔG) are performed to elucidate the underlying basic principles and investigate the effects of the solvent on the self-assembled structures. This approach will pave a predictive route for controlling the structures of assembly depending on the solvent polarity. In particular, we find that a binary solvent system with precisely controlled polarity induces directional assembly of the microsized Janus cylinders. Thus, the formation of two-dimensional (2D) and three-dimensional (3D) assembled clusters can be reliably tuned by controlling the numbers of constituent Janus cylinders in a binary solvent system. Finally, this approach is expanded to stepwise assembly, which forms unique microstructures via secondary growth of primary seed clusters formed by the Janus cylinders. We envision that this investigation is highly promising for the construction of desired superstructures using a wide variety of polymeric Janus microparticles with chemical and physical multicompartments.

In this paper, we present a fabrication method of polymeric multicompartment particles via a sequential micromolding process composed of injection of photocurable solution, evaporation of volatile solvent, and photo-polymerization. Depending on the concentration of volatile solvent in photocurable solution, the volume fraction of the multicompartment particles can be controlled. Also, the repetition of the sequential micromolding process with controlled composition of photocurable solution provides controlling the number of compartment in the particles. Based on this principle, we can fabricate single particles, Janus particles and triblock particles with desired fraction of the compartment. In addition, the multicompartment particles are able to be applicable for barcode particles embedding fluorescent dyes at each compartment. The barcode particles encode information about their specific compositions and enable simple identification. These sequential micromolding method for multicompartment particles has several advantages including easy, fast, and cost effective process. We envision that the multicompartment particles have various applications such as drug storage, delivery supporters, biosensors, and advanced materials for inducing highly selective adsorption-desorption.

: This study presents a micromolding for the synthesis of Janus particles with reconfigurable shape by pH stimuli. First, we use acrylic acid (AA) as pH responsive monomer in the hydrophilic part and trimethylolpropane triacylate (TMPTA) in the hydrophobic part, respectively. The change of acidity in solvent induces the swelling of hydrophilic part in the Janus particles. The pH-responsive Janus particles show different swelling ratio of hydrophilic part in according to composition of acrylic acid in diverse range (0-70% v/v) and pH (3-11). As the concentration of acrylic acid in the hydrophilic part and environmental pH increase, the hydrophilic part in the Janus particles is proportionally swelled. Second, we fabricate novel type of Janus particles with two different hydrophilicities. As a proof of concept, we have applied acrylic acid (AA) and 2-(dimethylamino)ethyl methacrylate (DAEMA) into each part because the monomers provide reverse responsive activity. As expected, these Janus particles show different shape anisotropies with reconfigurable property in accordance with the polarity of each part at same acidity of environmental solvent. We envision that the stimuli responsive Janus particles have a wide application from fundamental science to diagnostic apparatus.