Janus Particles: 1- Design and Preparation

In Roman religion, Janus was a god known as the custodian of the universe. He was usually shown with two heads in opposite sides to look in two directions at the same time. The term "Janus" is used to describe particles that have two faces with different physical or chemical characteristics. Janus particles with adjustable asymmetric structure and unique properties have attracted the attention of researchers. This anisotropy can lead to phenomena such as self-assembly or surface activity. since 1990s, Janus particles have been subjected to significant research. In this article, powerful synthesis methods including masking, phase separation and self-assembly, which are used to prepare Janus particles with different properties and morphologies, are described. This review focuses exclusively on Janus particles that contain polymeric materials. The different classes of synthesis methods of Janus particles, including some historical contexts, have been specially described. Also, in order to help new researchers in the field of making or using these particles, recent developments in this field have been described and the pros and cons of different methods have been evaluated with a view to future directions and applications.