Polyzwitterions with LCST Side Chains: Tunable Self-Assembly.

Manipulation of self-assembly behavior of copolymers via environmental change is attractive in the fabrication of smart polymeric materials. We present tunable self-assembly behavior of graft copolymers, poly(sulfobetaine methacrylate)--poly[oligo(ethylene glycol) methyl ether methacrylate)--di(ethylene glycol) methyl ether methacrylate] (PSBM--P(OEGMA--DEGMA)). Upon heating the aqueous solutions, the graft copolymers undergo a transition from micelles with PSBM cores to unimers (i.e., individual macromolecules) and then to reversed micelles with P(OEGMA--DEGMA) cores, thus demonstrating the tunability of the self-assembling through temperature change. In the presence of salt the temperature response of PSBM is eliminated, and the structure of the micelles with the P(OEGMA--DEGMA) core changes. Moreover, for the graft copolymer with long side chains, micelles with aggregation number 2 were formed with a PSBM core at low temperature, which is ascribed to the steric effect of the P(OEGMA--DEGMA) shell.