Preparation Of Fluorescent Microcapsule And Self-assembly Of Gradient Copolymer Based On Microfluidic Technology

Microfluidic technique is a novel technology of manipulating fluid and has amazing applications in many fields, including chemistry, biology and medicine. In recent years, glass capillary microfluidic device are playing more and more important role in the studies of microcapsule, microgel and self-assembly of copolymers, because of its easy fabrication and low cost.In one work, we designed a glass capillary microfluidic device and applied gas-liquid microfluidic technique to generate uniform-sized chitosan microcapsules with CdS quantum dots(QDs). CdS QDs were encapsulated into the liquid-core of the microcapsules and kept good fluorescence property. The sizes of the microcapsules prepared under different microfluidic parameters were characterized by using three-dimensional video microscopy. The responsiveness of fluorescent-microcapsule in CD solution was characterized by using fluorescence microscope. Moreover, the surface morphology of microcapsules was observed by a scanning electron microscopy in order to investigate the mechanism. The result shows the size of microcapsules decrease with the increasing gas flow rate but keep monodispersity. However, the liquid flow rate has not obvious effect on the size of the microcapsule. ?-Cyclodextrin(?-CD) causes the microcapsules to deform and even collapse. More interestingly, the fluorescence decay of microcapsules can be observed when immersed in ?-CD solution and the decay is more obvious with the increasing concentration of ?-CD solution. However, ?-cyclodextrin(?-CD) has little influence on the shape and fluorescent color of the microcapsules.In the other work, we designed a co-flow glass capillary microfluidic device and applied liquid-liquid microfluidic technique to study the self-assembly behavior of a gradient copolymer. Firstly, AA-TFEMA gradient copolymer was synthesized through RAFT emulsifier-free emulsion polymerization. The gradient structure of copolymer was characterized by 1H NMR and DSC. Then, AA-TFEMA gradient copolymer self-assembled in the co-flow microfluidic device. The flow rate of outer phase, total flow rate, copolymer concentration, water content of outer fluid and solvent had influence on the morphology of self-assembled structures, which was detected by TEM. The result shows that AA-TFEMA gradient copolymer form spherical and nonspherical aggregates in microfluidic device. The number of nonspherical aggregates obvious increase with the increasing flow rate of outer phase. The nonspherical morphologies are gradually disappeared as the water content in outer phase decreases. It is hard for the gradeint copolymers to self-assemble with low total flow rate. The transitions of Sphere-to-Rod and Rod-to-Visicle occur when the copolymer concentration increase in inner phase.