TIT# Quasiperiodicity in the nanoscopic morphology of some polyurethanes
AUT# Stribeck, Norbert; Li, Xuke; Eling, Berend; P”selt, Elmar;
     in 't Veld, Pieter J.;
SOU# J. Appl. Cryst. (2015), 48(2), 313-317
LOC# xv147
CLA#
COM# doi:10.1107/S1600576715000874
APP#
MAT#
ABS# Discrete small-angle X-ray scattering (SAXS) of soft matter generates a
     broad long-period peak related to distorted periodicity. In a special
     class of polyurethanes under varying strain a sequence of constant
     long-period bands is observed. The band positions form a Fibonacci
     sequence. This relates to the underlying chemical synthesis by
     polyaddition and indicates quasiperiodicity in sequences of stringed
     hard domains. These almost quasiperiodic sequences appear to be the
     probes provided by SAXS for the study of morphology evolution in such
     elastomers. Should a regular-as-possible arrangement of physical
     crosslinks optimize a property of the elastomer, then in the synthesis
     the number fraction $n_H$ of hard segments should be chosen $
     n_{H}=\tau/\left(1+\tau\right)\approx0.62$. $\tau$ is the golden ratio.