Preparation Of Photo-and Magneto-Dual Responsive Janus Particles And Their Tunable Morphology

Janus particles(JPs)are colloidal particles that have two or more chemical or physical properties at the same time.This unique structure of JPs allows it to have multiple functions and they have attracted great attention in the fields of optics,electricity,sensing,medicine,and catalysis.Recent studies have shown that in addition to chemical properties,physical properties play a vital role in many life processes.For example,non-spherical particles are more easily phagocytosed by cells than spherical particles,indicating the influence of particle morphology.Therefore,research on non-spherical particles is indispensable.However,most of JPs are spherical,and the current methods for preparing non-spherical JPs are mostly template methods.The process is cumbersome and inefficient,the size of JPs is not uniform and the control of morphology is ineffective.In view of the above problems,uniform photoresponsive azobenzene polymer poly[6-(4-methoxy-4'-oxyphenylazo)hexyl methacrylate](PMMAzo)microspheres were prepared by a microfluidic technology.Then micropheres were fixed on a specific substrate,and a thin layer of metallic nickel was deposited on the hemisphere of microspheres by physical vapor deposition.The JPs with photo-and magneto-dual responsiveness were obtained.Then,under a fixed magnetic field,morphology of the JPs was systematically studied by adjusting the radiation time,polarization angle and number of times of radiation of a specific wavelength of linearly polarized light.The spherical PMMAzo / Ni JPs were irradiated with a fixed polarized light with different directions(0°,30°,45°,60°,90°)in 30 minutes,and drop-shaped,snail-like,fusiform JPs could be obtained.Further,after a polarized light with different directions(0°,30°,45°,60°)in 10 minutes,the fusiform JP became a circular or hook-shaped particle.Morphological changes are related to the direction of polarized light,and the smaller the angle between the direction of the polarized light and the direction of the magnetic field,the more likely the transformation of the morphology occurs.After a polarized light with different directions(30°,45°,60°,90°)in 10 minutes,the droplet-like PMMAzo / Ni JPs became a hook-shaped or irregular shaped particle.In addition,the number of times the morphology transition is related to the direction of the polarized light.The drop-shaped,snail-like,fusiform,circular,hook-shaped,irregular shaped JPs can be prepared through quantifiable conditions,which is important for controlling non-spherical JPs.