Multi-axis alignment of Rod-like cellulose nanocrystals in drying droplets

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:603

Article

Pritchard, Cailean Q.^1,2  Navarro, Fernando²  Roman, Maren^2,3  Bortner, Michael J.^1,2 

[1] Virginia Tech, Dept Chem Engn, 245 Goodwin Hall,635 Prices Fork Rd, Blacksburg, VA 24061 USA

[2] Virginia Tech, Macromol Innovat Inst, Blacksburg, VA 24061 USA

[3] Virginia Tech, Dept Sustainable Biomat, Blacksburg, VA 24061 USA

关键词: Evaporation-induced self-assembly;    Cellulose nanocrystal;    CNC;    Rigid rod;    Radial alignment;    Tangential alignment;    PLM;   

DOI  :  10.1016/j.jcis.2021.06.069

来源: Elsevier

【 摘 要 】

Hypothesis: Radial capillary flow in evaporating droplets carry suspended nanoparticles to its periphery where they are deposited and form a coffee-ring. Rod-like nanoparticles seeking to minimize their cap-illary energy will align with their long-axis parallel to the contact line. Particles exhibiting electrostatic repulsion, such as cellulose nanocrystals (CNCs), establish a competition between capillary flow-induced impingement against a growing coffee-ring and entropic minimization leading to enhanced par-ticle mobility. Therefore, balancing these effects by manipulating the local particle concentration in dry-ing droplets should result in deposition with a controlled orientation of CNCs. Experiments: The dynamic local order in aqueous suspensions of CNCs in evaporating sessile droplets was investigated through time-resolved polarized light microscopy. The spatial distribution of alignment in deposited CNCs was explored as a function of nanoparticle concentration, droplet volume, initial degree of anisotropy, and substrate hydrophobicity. Computational analysis of the rotational Peclet number dur -ing evaporation was also investigated to evaluate any effects of shear-induced alignment. Findings: Multiple modes of orientation were identified suggesting local control over CNC orientation and subsequent properties can be attained via droplet-based patterning methods. Specifically, high local par-ticle concentrations led to tangential alignment and lower local particle concentrations resulted in new evidence for radial alignment near the center of dried droplets. (c) 2021 Elsevier Inc. All rights reserved.

【 授权许可】

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