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Please use this identifier to cite or link to this item: http://hdl.handle.net/2289/3571

Title: Phase behavior and dynamics of a micelle-forming triblock copolymer system
Authors: Mohan, Harsha P.
Bandyopadhyay, Ranjini
Issue Date: Apr-2008
Publisher: American Physical Society
Citation: Physical Review E, 2008, Vol.77, 041803
Abstract: Synperonic F-108 (generic name, "pluronic") is a micelle forming triblock copolymer of type ABA, where A is polyethylene oxide (PEO) and B is polypropylene oxide (PPO). At high temperatures, the hydrophobicity of the PPO chains increase, and the pluronic molecules, when dissolved in an aqueous medium, self-associate into spherical micelles with dense PPO cores and hydrated PEO coronas. At appropriately high concentrations, these micelles arrange in a face centered cubic lattice to show inverse crystallization, with the samples exhibiting high-temperature crystalline and low-temperature fluidlike phases. By studying the evolution of the elastic and viscous moduli as temperature is increased at a fixed rate, we construct the concentration-temperature phase diagram of Synperonic F-108. For a certain range of temperatures and at appropriate sample concentrations, we observe a predominantly elastic response. Oscillatory strain amplitude sweep measurements on these samples show pronounced peaks in the loss moduli, a typical feature of soft solids. The soft solidlike nature of these materials is further demonstrated by measuring their frequency-dependent mechanical moduli. The storage moduli are significantly larger than the loss moduli and are almost independent of the applied angular frequency. Finally, we perform strain rate frequency superposition experiments to measure the slow relaxation dynamics of this soft solid.
Description: Open Access.
URI: http://hdl.handle.net/2289/3571
ISSN: E-ISSN: 1550-2376
P-ISSN: 1539-3755
Alternative Location: http://dx.doi.org/10.1103/PhysRevE.77.041803
http://arxiv.org/abs/0710.3433
Copyright: 2008 American Physical Society
Appears in Collections:Research Papers (SCM)

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