Dynamical Arrest, Percolation, Gelation, and Glass Formation in Model Nanoparticle Dispersions with Thermoreversible Adhesive Interactions

Published

January 9, 2012

Author(s)

Aaron Paul Rust Eberle, Ramon Castaneda-Priego, Jung M. Kim, Norman J. Wagner

Abstract

We report an experimental study of the dynamical arrest transition for a model system consisting of octadecyl coated silica suspended in n-tetradecane from dilute to concentrated conditions spanning the state diagram. The dispersion's interparticle potential is tuned by temperature affecting the brush conformation leading to a thermoreversible model system. The dynamical arrest transition temperature, T*, is determined as a function of dispersion volume fraction by small-amplitude dynamic oscillatory shear (SAOS) rheology. We corroborate this transition temperature by measuring a power-law decay of the autocorrelation function and a loss of ergodicity via fiber-optic quasi-elastic light scattering (FOQELS). The structure at T* is measured using small-angle neutron scattering (SANS). The scattering intensity is fit to extract the interparticle pair-potential using the Ornstein-Zernike equation with the Percus-Yevick closure approximation, assuming a square well interaction potential with a short range interaction (1% of particle diameter).1 The strength of attraction is characterized using the Baxter temperature2 and mapped onto the adhesive hard sphere (AHS) state diagram. The experiments show a continuous dynamical arrest transition line that follows the predicted dynamical percolation line until  0.41 where it subtends the predictions toward the mode coupling theory (MCT) attractive-driven glass (ADG) line. An alternative analysis of the phase transition through the reduced second virial coefficient B2* shows a change in the functional dependence of B2* on particle concentration around  0.36. We propose this signifies the location of a gel-to-glass transition. The results presented herein differ from those observed for depletion flocculated dispersion of micron-sized particles in polymer solutions, where dynamical arrest is a consequence of multicomponent phase separation, suggesting dynamical arrest is sensitive to the physical mechanism of attraction.

Citation

Langmuir

Volume

28

Issue

3

Pub Type

Journals

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DOI Link

Citation

Eberle, A. , Castaneda-Priego, R. , Kim, J. and Wagner, N. (2012), Dynamical Arrest, Percolation, Gelation, and Glass Formation in Model Nanoparticle Dispersions with Thermoreversible Adhesive Interactions, Langmuir, [online], https://doi.org/10.1021/la2035054 (Accessed February 17, 2025)