Rheological studies on mesomorphic poly(diethylsiloxane) melts

Saxena, Himanshu; Hedden, Ronald C.; Cohen, Claude

doi:10.1122/1.1495492

Cited by 1 publication

(1 citation statement)

References 29 publications

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“…We further identify regime 2, which is characterized by G ′ > G ′′ , but where the magnitudes of both moduli are significantly lower than those seen in the third regime, as a coexistence region between the micellar fluid and grains of solid crystalline phases, analogous to the phase observed in the diblock copolymer system E 87 B 18 [24]. We should note here that similar frequency-dependence of the mechanical moduli observed in recent rheology studies performed by Saxena et al on poly(diethylsiloxane) melts [36] have been attributed to the presence of mesophase domains that serve as effective crosslinks in the melt.…”

Section: B Rheological Measurementssupporting

confidence: 79%

Phase behavior and dynamics of a micelle-forming triblock copolymer system

Mohan

Bandyopadhyay

2008

Phys. Rev. E

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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 centred 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 solid-like 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 (SRFS) experiments to measure the slow relaxation dynamics of this soft solid.

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Section: B Rheological Measurementssupporting

confidence: 79%