Hydrophobic/Hydrophilic Cooperative Janus Branched Polymer Fibers with Controllable Length and Density of Nanobranches

Abstract The fabrication of a fiber with multilevel micro‐/nanostructures is still a great challenge. Here, a newly structured polymer fiber, which possesses both a hydrophobic/hydrophilic cooperative Janus stem and nanosized branches with controllable length and density, is developed via a microfluidic‐electrospinning technology for the first time. Both the length and density of the branches on the fiber can be controlled by changing the electrical conductivity of the inner phase of poly(vinyl alcohol) solution or the applied voltage. The mechanical analytic model reveals that when the coulomb force between surface charge of continuous phase and volume charge of dispersed phase, which is raised with the electrical conductivity of the inner phase or the applied voltage increasing, is greater than surface tension of continuous phase, the branches are formed; simultaneously, the Janus structure is generated through both the electrostatic repulsion and phase separation.