Pickering emulsions stabilized by cellulose nanocrystals grafted with thermo-responsive polymer brushes

JOURNAL OF COLLOID AND INTERFACE SCIENCE

卷:369

Article

Zoppe, Justin O.¹  Venditti, Richard A.¹  Rojas, Orlando J.^1,2 

[1] N Carolina State Univ, Dept Forest Biomat, Raleigh, NC 27697 USA

[2] Aalto Univ, Dept Forest Prod Technol, Fac Chem & Mat Sci, FI-00076 Aalto, Finland

关键词: Pickering emulsions;    Oil-in-water emulsions;    Cellulose nanoparticles;    Cellulose nanocrystals;    Thermo-responsive emulsions;    Poly(N-isopropylacrylamide);    LCST;    Grafts;    Surface-initiated single-electron transfer;    living radical polymerization;   

DOI  :  10.1016/j.jcis.2011.12.011

来源: Elsevier

【 摘 要 】

Cellulose nanocrystals (CNCs) from ramie fibers are studied as stabilizers of oil-in-water emulsions. The phase behavior of heptane and water systems is studied, and emulsions stabilized by CNCs are analyzed by using drop sizing (light scattering) and optical, scanning, and freeze-fracture electron microscopies. Water-continuous Pickering emulsions are produced with cellulose nanocrystals (0.05-0.5 wt%) grafted with thermo-responsive poly(NIPAM) brushes (poly(NIPAM)-g-CNCs). They are observed to be stable during the time of observation of 4 months. In contrast, unmodified CNCs are unable to stabilize heptane-in-water emulsions. After emulsification, poly(NIPAM)-g-CNCs are observed to form aligned, layered structures at the oil-water interface. The emulsions stabilized by poly(NIPAM)-g-CNCs break after heating at a temperature above the LCST of poly(NIPAM), which is taken as indication of the temperature responsiveness of the brushes installed on the particles and thus the responsiveness of the Pickering emulsions. This phenomenon is further elucidated via rheological measurements, in which viscosities of the Pickering emulsions increase on approach of the low critical solution temperature of poly(NIPAM). The effect of temperature can be counterbalanced with the addition of salt which is explained by the reduction of electrostatic and steric interactions of poly(NIPAM)-g-CNCs at the oil-water interface. (C) 2011 Elsevier Inc. All rights reserved.

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