Communications to the editor

Abstract

One of the most widely investigated temperature-sensitive polymers is Pluronic, which is poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) (PEO-PPO-PEO) triblock copolymer.1 The aqueous solution of Pluronic showed sol-to-gel (lower temperature region) and gel-to-sol (higher temperature region) transition behaviors with increasing temperature,2 and it is proposed that Pluronic had possibility to be used as injectable drug delivery system.3 The transition behaviors were studied by many researchers with various instruments such as light scattering,4 SANS,5 UV,6 DSC,7 cryo-TEM,8 dielectric measurement,9 and rheology,10. It has been proved that the transition behavior is due to the formation of micelle and micelle packing over specific temperature and concentration.1-10 However, Pluronic was limited in use as injectable drug

delivery system because of its nondegradability, toxicity, and dissolution of the gel after administration.11