Nano-Segregation of Squalane between Smectic Layers of Rigid-Rod Polysilane

Abstract

It has been theoretically predicted that spherical particles added to the smectic phase formed by rod-like particles segregate between the smetic layers and significantly enhance the stability of the smectic phase due to an entropic effect based on the steric repulsion between the particles, which is referred to as the depletion effect. In this study, we describe the first experimental verification of the theoretical prediction, in which the binary mixtures of the rod-like polymer, poly[n-decyl-(S)-2-methylbutylsilane] (PDMS), with narrow molecular weight distributions, and a spherical branched alkane, squalane, were investigated by synchrotron radiation small-and wide-angle X-ray scattering (SR-SAXS and SR-WAXS) and atomic force microscopy (AFM) observations and found to reproduce the predicted segregation between the smectic layers.

Smectic–Smectic Phase Segregation Occurring in Binary Mixtures of Long and Short Rigid-Rod Helical Polysilanes

“…The insertion of spherical particles between smectic layers of rodlike particles in the mixture has been theoretically predicted , and experimentally demonstrated. − A smectic layer of short particles inserted between the smectic layers of long particles was also theoretically predicted in a binary mixture of long and short rodlike particles, which was also reproduced in a binary mixture of long and short polysilanes with a molecular-weight ratio of approximately 3 . Although it is not known why the short polymer with the broad molecular-weight distribution inserts between the smectic layers of the long polymer, it is possible that smaller molecular-weight fractions, which behave as spherical particles, are selectively inserted between the layers.…”