Orientational order of carbon nanotube guests in a nematic host suspension of colloidal viral rods

TL;DR

This study investigates how carbon nanotubes align within a nematic suspension of viral rods, revealing that nanotubes are less ordered than the host viruses, consistent with theoretical predictions accounting for particle flexibility and size variation.

Contribution

It provides the first experimental validation of Onsager-type theory for guest-host nematic systems with flexible and polydisperse particles.

Findings

Carbon nanotubes exhibit lower orientational order than viral hosts.

Experimental results agree with Onsager-type theoretical predictions.

The degree of order varies systematically across the nematic range.

Abstract

In order to investigate the coupling between the degrees of alignment of elongated particles in binary nematic dispersions, surfactant stabilized single-wall carbon nanotubes (CNTs) have been added to nematic suspensions of colloidal rodlike viruses in aqueous solution.We have independently measured the orientational order parameter of both components of the guest-host system by means of polarized Raman spectroscopy and by optical birefringence, respectively. Our system allows us therefore to probe the regime where the guest particles (CNTs) are shorter and thinner than the fd virus host particles. We show that the degree of order of the CNTs is systematically smaller than that of the fd virus particles for the whole nematic range. These measurements are in good agreement with predictions of an Onsager-type second-viral theory, which explicitly includes the flexibility of the virus particles, and the polydispersity of the CNTs.