Structure-property relationship of a soft colloidal glass in simple and mixed flows

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:601

Article

Calabrese, Vincenzo¹  Varchanis, Stylianos^1,2  Haward, Simon J.¹  Tsamopoulos, John²  Shen, Amy Q.¹ 

[1] Okinawa Inst Sci & Technol Grad Univ, 1919-1 Tancha, Onna Son, Okinawa 9040495, Japan

[2] Univ Patras, Dept Chem Engn, Lab Fluid Mech & Rheol, Patras 26500, Greece

关键词: Cellulose nanocrystals;    Anisotropic soft materials;    Microfluidics;    Negative wake;    Liquid crystal;    Complex flows;    Shear banding;    Plasticity;    Flow past a cylinder;   

DOI  :  10.1016/j.jcis.2021.05.103

来源: Elsevier

【 摘 要 】

Hypothesis: Under specific conditions, rod-like cellulose nanocrystals (CNC) can assemble into structurally ordered soft glasses (SGs) with anisotropy that can be controlled by applying shear. However, to achieve full structural control of SGs in real industrial processes, their response to mixed shear and extensional kinematics needs to be determined. We hypothesise that by knowing the shear rheology of the CNC-based soft glass and adopting a suitable constitutive model, it is possible to predict the structure-property relationship of the SG under mixed flows. Experiments: We use an aqueous suspension with 2 wt% CNC at 25 mM NaCl to form a structurally ordered SG composed of a CNC network containing nematic domains. We combine rheometry and microfluidic experiments with numerical simulations to study the flow properties of the SG in shear, extension, and mixed flow conditions. Extensional flow is investigated in the Optimised Shape Cross slot Extensional Rheometer (OSCER), where the SG is exposed to shear-free planar elongation. Mixed flow kinematics are investigated in a benchmark microfluidic cylinder device (MCD) where the SG flows past a confined cylinder in a microchannel. Findings: The SG in the MCD displays a velocity overshoot (negative wake) and a pronounced CNC alignment downstream of the cylinder. Simulations using the thixotropic elasto-visco-plastic (TEVP) model yield near quantitative agreement of the velocity profiles in simple and mixed flows and capture the structural fingerprint of the material. Our results provide a comprehensive link between the structural behaviour of a CNC-based SG and its mechanistic properties, laying foundations for the development of functional, built-to-order soft materials. (c) 2021 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

【 授权许可】

Free