Pluronics^TM

Pluronics^TM are a family of triblock copolymers, each containing a block of polyethylene oxide (PEO) covalently bound to a block of polypropylene oxide (PPO) which is bound to another block of polyethylene oxide (i.e., PEO-PPO-PEO).



Individual PEO and PPO chains demonstrate an inverse temperature solubility in water, i.e., these chains are more soluble at low temperatures than higher temperatures. PPO is comparatively less soluble than PEO. Consequently there exists intermediate temperatures where the PPO middle block would not stay into solution if it were not for its PEO neighbors. To minimize unfavorable water-PPO interactions, several Pluronic^TM molecules come together to form a micelle. In the form of spherical micelles, Pluronics^TM consists of a PPO core surrounded by a PEO corona. By changing concentration, the solution becomes packed with micelles and can even form well ordered so-called micellar crystals. Thus, by changing temperature and concentration one can transition from a viscoelastic liquid to a viscoelastic solid.