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HomeSolid State PhenomenaSolid State Phenomena Vol. 184Mechanical Relaxation Studies of Sub-Rouse Modes...

Mechanical Relaxation Studies of Sub-Rouse Modes in Amorphous Polymers

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Abstract:

Mechanical spectroscopy is a powerful tool for the investigation of molecular dynamics of amorphous polymers over a large temperature range and frequency scale. In this work, by using high precision shear mechanical spectroscopy tool, we have investigated the segmental dynamics from local segmental relaxation to sub-Rouse modes in a series of amorphous polymers. We have demonstrated the existence of sub-Rouse modes slower than the local segmental motion in amorphous polymers. The sub-Rouse modes exhibit a similar change of dynamics at the same temperature T_B~1.2 T_g, as the local segmental relaxation through the temperature dependence of relaxation time and relaxation strength. Furthermore, the crossover relaxation time of the sub-Rouse modes at T_B is almost the same for all the polymers investigated, i.e. τ_α'(T_B) = 10^-1±0.5 s, which is independent of molecular weight and molecular structure. This remarkable finding indicates that solely the time scale of the relaxation determines the change in dynamics of the sub-Rouse modes. According to the coupling model, the crossover is suggested to be caused by the onset of strong intermolecular cooperativity below T_B. Hence the results suggest that the sub-Rouse modes and their properties are generally found in amorphous polymers by mechanical spectroscopy, and reveal the cooperative nature of the sub-Rouse modes.

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Periodical:

Solid State Phenomena (Volume 184)

Pages:

52-59

DOI:

https://doi.org/10.4028/www.scientific.net/SSP.184.52

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Online since:

January 2012

Authors:

Xue Bang Wu, Hua Guang Wang, Chang Song Liu, Zhen Gang Zhu

Keywords:

Amorphous Polymers, Mechanical Spectroscopy, Sub-Rouse Modes

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© 2012 Trans Tech Publications Ltd. All Rights Reserved

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