Speaker
Description
In recent years, a great effort has been put to investigate collective relaxations in liquids [1] and polymer systems [2] at mesoscopic scales. This has been experimentally achieved using neutron scattering methods, especially in combination with polarization analysis (PA) capabilities [3] allowing to disentangle incoherent and coherent contributions, or with computational methods [4]. Few neutron spectrometers currently allow PA, and the method has also limitations due to reduced neutron flux. Here we present the results of the investigation of a crosslinked rubber of deuterated 1,2-polybutadiene (d1,2-PB), where we use an alternative approach and combine different neutron spectrometers to separate self and collective dynamics [5]. In the neat polymer melt the collective segmental relaxation around the structure factor peak S(Qmax) shows de Gennes narrowing, with a collective relaxation time τc(Q) that increases without plateauing towards lower Qs. In the crosslinked d1,2-PB rubber, the peak at S(Qmax) is reduced and instead a strong low-Q peak emerges. Both the collective d1,2-PB relaxation rates around the former S(Qmax) and the relaxation around the new crosslink correlation peak are significantly slowed down compared to the melt. Finally, the cross-linking strands exhibit their own fast dynamics, which is well described by diffusion within a spherical Gaussian well.
| Session | Soft Condensed Matter |
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