Direct imaging of single-walled carbon nanotubes reptational dynamics in packed-colloid porous media

Understanding Brownian dynamics of single-walled carbon nanotubes (SWCNTs) in complex porous media is key to understanding transport and mechanical properties in a variety of systems. Motion of semi-flexible filaments in gel-like porous media including polymer networks and cell cytoskeleton have been studied theoretically and experimentally, whereas the motion of these materials in packed-colloid porous media, advanced foams, super-cooled and rock-like systems have not been thoroughly studied. In this thesis, we use near infrared fluorescent video microscopy to directly visualize the reptation and transport of intrinsically fluorescent, semiflexible, semiconducting single-walled carbon nanotubes (SWCNT) in the sub-micron pores of randomly packed colloids as fixed obstacles of packed-colloid porous media. In packed-colloid pores, we find SWCNTs diffuse along straight pores and bend across pores; conversely, in gel pores, SWCNTs consistently diffuse in curved pores, displaying faster parallel motion. We find that pore heterogeneity causes wide distributed SWCNT disentanglement time between pores, which causes SWCNT location dependent Brownian rotation dynamics from subdiffusive to diffusive regime. By studying the orientation and SWCNT pore disentanglement in packed-colloid pore, we study how the properties of the environment, like pore orientation distribution of the porous media, affect SWCNT mobility through SWCNT bending angle. These results show that the widely distributed number of available pore orientations of each pore location directly affect SWCNT Brownian dynamics. We further study SWCNT Brownian dynamics in hexagonally packed-colloid pore to minimize pore heterogeneity effect. Consistent large number of available pore orientations enables multiple SWCNT disentanglement time, thus makes SWCNT has consistently long-time diffusive rotation dynamics. SWCNT Bending plays an important role in disentanglement between packed-colloid pores. We study SWCNT bending through Fourier mode of backbone points. In hexagonally packed-colloid pores, we find that the variance of SWCNT Bending Fourier mode is purely thermal under pore confinement. In highly bent pores, SWCNT displays non-equilibrium bending because of long-time highly curved pore caging. Jumps of bending mode amplitude from cage potential leads to subdiffusive bending mode amplitude growth. Our measure on cage potential shows the SWCNT can escape cage from potential of any curvature at room temperature. This result matches our observation that SWCNT bending mode is a pore independent continuous time random walk in hexagonally packed-colloid pores. Our result shows that Odijk regime still hold in porose space with lower porosity.

Name thesis:degree_name

Doctor of Philosophy

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Engineering

Grantor

Rice University

Year dc:date.issued

2022

Author dc:creator

• Tang, Zhao

Advisor dc:contributor.advisor

• Pasquali, Matteo

• SWCNT
• Brownian Motion

Statement dc:rights

• Copyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.

Language dc:language.iso

eng

Handle dc:identifier.uri

https://hdl.handle.net/1911/113326

OAI identifier oai:identifier

oai:repository.rice.edu:1911/113326