Flow-induced synthesis of polystyrene–block–poly(ethylene glycol) vesicles on the interface of a laminated microflow

Abstract

This paper presents a microfluidic synthesis of polymeric vesicles (PVs) by employing flowinduced self-assembly of polystyrene-block-poly(ethylene glycol) (PS-b-PEG) in a double flow-focusing microchannel (DFFM). The DFFM can solve the limitation of a large size distribution of produced PVs caused by clogging issues in general microchannel synthesis. By adding an attenuation layer between the polymer-dissolved solution and water, it is determined that rapid self-assembly of the polymers can be controlled. The hollow PVs are synthesized with a narrow size distribution and the size controllability is also examined for the ratios of the inlet flow rates and the polymer concentration. The produced PVs are characterized by using transmission electron microscopy, scanning electron microscopy and dynamic light scattering. It is newly visualized that the self-assembly occurs mostly in the attenuation layer owing to the diffusion through the interfaces of the five parallel laminar flow formed in the DFFM. This finding can provide a significant clue to understand the inflow-induced synthesis of the PVs in microchannels. Also, the uniform PVs can be applied to the development of drugs and biomedical researches.

Microfluidic Tracking of the Growth of Polymeric Vesicles in Hydrodynamic Flow

“…Different from the previous studies, here we introduce water into the center flow in the DFFM and the water stream was focused on the solvent and polymer stream. This can make the formation of PVs occur in the center of the channel width to prevent channel clogging issues from occurring in the SFFM . The water stream was then focused by the pure solvent solution stream of N , N -dimethylformamide (DMF) and the polymer-dissolved solution stream at the first focusing junction and the second focusing junction, respectively.…”

“…This can make the formation of PVs occur in the center of the channel width to prevent channel clogging issues from occurring in the SFFM. 47 The water stream was then focused by the pure solvent solution stream of N,N-dimethylformamide (DMF) and the polymer-dissolved solution stream at the first focusing junction and the second focusing junction, respectively. A stable laminar flow was formed along the microchannel after the second focusing junction and is observed in Figure 1a.…”

“…Previously, we have demonstrated that the higher the shear stress is, the lower the size of the formed PVs can be obtained. 47 This may be attributed to the fact that the growth of disklike micelles is limited in high shear stress and this resulted in the smaller size of the formed PVs.…”