S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Chemical and Biological Engineering (화학생물공학부) Journal Papers (저널논문_화학생물공학부)
Phase Behavior of a PEO-PPO-PEO Triblock Copolymer in Aqueous Solutions: Two Gelation Mechanisms
- Park, Moon Jeong; Char, Kookheon; Kim, Hong Doo; Lee, Chang-Hee; Seong, Baek-Seok; Han, Young-Soo
- Issue Date
- 한국고분자학회 = The Polymer Society of Korea
- Macromol. Res., 10, 325 (2002)
- Phase behavior of a PEO-PPO-PEO (Pluronic P103) triblock copolymer in water is investigated using small-angle neutron scattering (SANS), small-angle X-ray scattering (SAXS), dynamic light scattering (DLS) and rheology. Pluronic P103 shows apparent two gel states in different temperature regions. The first sol-to-gel transition at a lower temperature (i.e., the hard gel I state) turns out to be the hexagonal microphase as evidenced by the combined SANS and SAXS and the frequency dependence of both G' and G" in rheology. In contrast to the hard gel I, the second sol-to-gel transition (i.e., the hard gel I1 state) at a higher temperature represents the block copolymer micelles in somewhat disordered state rather than the ordered state seen in the hard gel I. Moreover, turbidity change depending only on the temperature with four distinct regions is observed and the large aggregates with size larger than 5,000 nm are detected with DLS in the turbid solution region. Based upon the present study, two different gelation mechanisms for aqueous PEO-PPO-PEO triblock copolymer solutions are proposed.