Dynamics of 8CB confined into porous silicon probed by incoherent neutron backscattering experiments

TL;DR

This study investigates how nanochannel confinement in porous silicon alters the phase behavior and molecular dynamics of liquid crystal 8CB, revealing persistent short-range order and hindered molecular mobility across temperatures.

Contribution

It provides new insights into the effects of nano-confinement on liquid crystal dynamics and phase behavior using incoherent neutron scattering techniques.

Findings

Development of short-range smectic order over broad temperature range

Significant reduction in molecular mobility at high temperatures

Progressive slowdown and growth of static correlation length upon cooling

Abstract

Confinement in the nanochannels of porous silicon strongly affects the phase behavior of the archetype liquid-crystal 4-n-octyl-4-cyanobiphenyl (8CB). A very striking phenom- enon is the development of a short-range smectic order, which occurs on a very broad temperature range. It suggests in this case that quenched disorder effects add to usual finite size and surface interaction effects. We have monitored the temperature variation of the molecular dynamics of the confined fluid by incoherent quasielastic neutron scat- tering. A strongly reduced mobility is observed at the highest temperatures in the liquid phase, which suggests that the interfacial molecular dynamics is strongly hindered. A continuously increasing slowdown appears on cooling together with a progressive growth of the static correlation length