A brief review of 'schizophrenic' block copolymers

Recent progress in the synthesis of so-called 'schizophrenic' water-soluble block copolymers is reviewed. The original report in this new sub-field involved a tertiary amine methacrylate-based AB diblock copolymer synthesized by group transfer polymerization that was both pH- and salt-responsive, allowing the formation of either A-core or B-core micelles in aqueous solution. A second example involved a poly(propylene oxide)-tertiary amine methacrylate diblock copolymer synthesized via atom transfer radical polymerization (ATRP) that exhibited both pH- and thermo-responsive behavior. More recently, several examples of wholly pH-responsive zwitterionic diblock copolymers (prepared via ATRP, usually using protecting group chemistry) have been reported, with their aqueous solution behavior being characterized with varying degrees of precision. The synthesis and characterization of purely thermo-responsive diblock copolymers is also discussed, along with the first example of an ABC triblock copolymer that is capable of forming a 'trinity' of micelles in aqueous solution at 20 °C simply by adjusting the solution pH. In this remarkable final example, the cores of the three types of micelles are formed by hydrophobic forces, polyion complexation and hydrogen bonding, respectively.