TIT# Wide-Angle Scattering Halo Analysis and the Evolution of Oriented Amorphous
     Structure after Elongation Jumps in some Elastomers
AUT# Stribeck, Almut; Schneider, Konrad; Pöselt, Elmar; Eling, Berend; Roth Stephan V.;
SOU# Macromol. Chem. Phys. (2022), submitted
DOI#
LOC# xv166
CLA#
COM#
APP#
MAT#
ABS# Amorphous and low-crystallinity thermoplastic polyurethane elastomers are
     shot back and forth between two elongation levels (\epsilon=0.2 and 
     \epsilon=1.2) and observed between the excitations for 10 s using 
     wide-angle X-ray scattering (WAXS) (50 Hz). For orientation analysis, the
     fiber patterns are projected, expanded in multipoles, and discussed as a
     function of relaxation time. Normalized WAXS suggests that the oriented 
     halo observed during extension is predominantly due to selective extinction
     of unfavorably oriented probes (chain bundles). During retraction, 
     neighborhoods and thus clusters are restored. Discussed are the relaxation
     curves depending on material and the number of load cycles. The separation
     of the halo into narrow rings introduces  “bundle airiness” as a second
     coordinate. The now bivariate cluster density is the product of two 
     univariate functions. Its factor "airiness distribution" seems to be a 
     material property which is not changed by annealing. In contrast, the 
     bivariate preferred orientation is not product-separable. Especially with 
     harder materials it shows 2 bundle ensembles of different airiness. 
     Interactions between the ensembles explain complex trajectories of the 
     orientation-relaxation curves. The formation of the additional airier 
     oriented component is inhibited by annealing in most of the materials 
     studied. In contrast, multiple load changes promote its formation.