Zwitterionic amphiphiles: their aggregation behavior and applications
Zwitterionic amphiphiles with covalently bonded anionic and cationic groups exhibit electrically neutral properties but extremely high polarity. Under most circumstances, their charge densities can be simply and reversibly modulated by pH values. Such unique structures and properties distinguish them from all other types of amphiphiles. In this review, we summarize the assembly characteristics of zwitterionic amphiphiles and put forward our important fundamental opinions on how to design and modify zwitterionic amphiphiles to achieve abundant aggregate structures and multifunctions. More importantly, this kind of amphiphile shows mildness, better wettability, good biocompatibility, biostability, nonfouling and functionalizable properties, as well as an excellent synergistic effect with other amphiphiles, which makes them promising candidates for applications in household cleaning, cosmetics, electrochemistry, intelligent soft materials and biology. Based on the matchless advantages of zwitterions, we focus on the introduction of zwitterionic betaine and imidazolium amphiphiles and explore their applications in target ion conduction, noble metal nanomaterials and antifouling biomaterial preparation. As far as we know, there has been no review of the aggregation behavior and green applications of zwitterionic amphiphiles so far. We expect to provide readers with a comprehensive overview of their assembly strategies, practical methodologies and future potential progression, as well as to promote greater interest and further developments in this field.