The
understanding of the shell formation mechanism for the novel
encapsulation technique via integrating microfluidic T-junction and
interfacial polymerization is not only important to fabricate high-quality
polyamine microcapsules but also of practical and theoretical significance
to the wide application of this method based on nonequilibrium droplets.
Herein, using pure polyamine as a targeting core, the shell formation
mechanism was investigated by studying the achieved shell structures
of the preliminary and final microcapsules and the behavior of nonequilibrium
polyamine droplets in the coflow solvent. It reveals the shell has
a multilayered structure, i.e., a rough outer layer, a porous middle
layer, and a thin but dense inner layer, and the porous middle layer
consists of pores with two size levels. This shell structure was correlated
to fractal geometry of the polyamine droplet before being encapsulated,
which was generated attributed to the interactions between the nonequilibrium
polyamine droplet and the coflow solvent, i.e., interdiffusion and
spontaneous emulsification. To achieve robust microcapsules, shell
thickness and tightness were also studied by varying the composition
of the reaction solution in terms of diisocyanate concentration and
type of solvent with different polarity. The effect of these two key
parameters on shell in this method is very similar to that in the
traditional interfacial polymerization. In addition, the influence
of the shell-forming stage and shell-growth stage on the robustness
of microcapsule was discussed, indicating the former is decisive.
The quality of microcapsules directly determines the performance of microcapsule‐based functional materials, such as self‐healing materials. How to achieve high‐quality microcapsules depends on not only the selected microencapsulation technique but also the process regulation. Herein, using tetraethylenepentamine (TEPA) as the core target to be encapsulated by a novel microencapsulation technique through integrating microfluidic T‐junction and interfacial polymerization, this investigation studied how the process parameters influence the microencapsulation process and the quality of the synthesized microcapsules regarding the size, morphology, shell structure, and composition. The studied parameters include the solvent type and surfactant concentration in the co‐flow solution, the fed volume of the co‐flow solution, the types of the solvent, catalyst, and shell‐forming monomer in the reaction solution for the shell‐growth stage, and the reaction temperature at the shell‐growth stage. The influence mechanisms were established based on the observations, and the optimized parameter combination for the process was achieved. Through the parametric study for the microencapsulation technique, this study also lays a solid foundation for the technique to fabricate microcapsules containing other functional substances with high quality.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.