Ethylcellulose Colloids Incubated in Dilute Solution

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• 作者：Han-Liou Yi ; Liang-Je Lai ; Jung-Shiun Jiang ; Chi-Chung Hua
• 刊名：Journal of Physical Chemistry B
• 出版年：2017
• 出版时间：January 26, 2017
• 年：2017
• 卷：121
• 期：3
• 页码：638-648
• 全文大小：667K
• ISSN：1520-5207

文摘

This study revealed, for the first time, that dilute solutions made of a representative series of commercial ethylcellulose (EC; molecular weights 77–305 kDa, provided by the manufacturer) and four distinct organic solvents (α-terpineol, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (TPIB), tetrahydrofuran (THF), and benzene) can be used to foster stabilized, nearly monodisperse, nanoscale (pure) polymer colloid, with no isolated chains present. Using combined light-scattering (dynamic light scattering, static form factor, and Zimm/Berry plots) and intrinsic viscosity (Tanglertpaibul–Rao, Huggins, and Kraemer plots) analyses, the structural features of colloidal EC aggregates, ρ = ⟨R_g⟩/⟨R_h⟩ = 0.67–0.83, were first shown to be described rather well by the theory on colloidal spheres (⟨R_g⟩ and ⟨R_h⟩ being the mean radius of gyration and the hydrodynamic radius, respectively). An empirical scaling law relating the intrinsic viscosity to the mean colloid size can thus be established: [η]_H = (1.7 ± 0.2) ×10^–3 ⟨R_h⟩^(2.1±0.3) ([η]_H and ⟨R_h⟩ in units of mL/g and nm, respectively), which may be contrasted with the Zimm model for isolated Gaussian coils, [η]_H ∼ ⟨R_h⟩¹, and the Einstein equation for isolated solid spheres, [η]_H ∼ ⟨R_h⟩⁰. Optical microscopy images of thin films cast from different EC solutions clearly revealed the abundance of micron EC agglomerates, contrary to the uniform thin-film morphology produced from a dilute polystyrene solution, which serves as a reference solution composed of isolated chains. These observations point to new features and applications of EC dispersions.