Self-assembly of Amphiphilic Azo Polymers in Solutions

Amphiphilic polymers are polymers composed of hydrophilic and the hydrophobic structural units. The hydrophilic groups can be carried by azo chromophores or more commonly attached on the other parts of the polymers. Amphiphilic azo polymers include homopolymers, random copolymers, block and grafted copolymers, star-like polymers, tadpole-shaped polymers and dendritic polymers. Amphiphilic polymers can be considered as synthetic counterparts of ubiquitous amphiphilic compounds in nature such as lipids and proteins. Amphiphilic polymers, especially block copolymers, can form a variety of order aggregates, such as micelles and vesicles. When compared to micelles from traditional surfactants, polymeric self-assemblies have recently been recognized for advantages such as superior stability, toughness and micellization depending on selective solvents. In many instances, the morphology of the polymeric self-assembly and its application are closely related. Thus, controlling the morphology of the assembled structures from block copolymers is of great practical value. Self-assembled polymeric materials with well-defined structures such as spheres, rods, vesicles, lamellas and other nanostructures have attracted increasing interests recently due to their potential applications in biomedical engineering, electronics and optics. The self-assembled structures of azo polymers can undergo structural changes both in solution and in the solid state when triggered by light or other external stimuli. Understanding the self-assembling processes can lead to the development of photo responsive materials with new functions for future applications. In this review the self-assembly of amphiphilic azo polymers in solutions are reported.