Dual Responsive Pickering Emulsion Stabilized by Poly[2-(dimethylamino)ethyl methacrylate] Grafted Cellulose Nanocrystals

Abstract

A weak polyelectrolyte, poly[2-(dimethylamino)ethyl methacrylate] (PDMAEMA), was grafted onto the surface of cellulose nanocrystals via free radical polymerization. The resultant suspension of PDMAEMA-grafted-cellulose nanocrystals (PDMAEMA-g-CNC) possessed pH-responsive properties. The grafting was confirmed by FTIR, potentiometric titration, elementary analysis, and thermogravimetric analysis (TGA); the surface and interfacial properties of the modified particles were characterized by surface tensiometer. Compared to pristine cellulose nanocrystals, modified CNC significantly reduced the surface and interfacial tensions. Stable heptane-in-water and toluene-in-water emulsions were prepared with PDMAEMA-g-CNC. Various factors, such as polarity of solvents, concentration of particles, electrolytes, and pH, on the properties of the emulsions were investigated. Using Nile Red as a florescence probe, the stability of the emulsions as a function of pH and temperature was elucidated. It was deduced that PDMAEMA chains promoted the stability of emulsion droplets and their chain conformation varied with pH and temperature to trigger the emulsification and demulsification of oil droplets. Interestingly, for heptane system, the macroscopic colors varied depending on the pH condition, while the color of the toluene system remained the same. Reversible emulsion systems that responded to pH were observed and a thermoresponsive Pickering emulsion system was demonstrated.

Holocellulose Nanocrystals: Amphiphilicity, Oil/Water Emulsion, and Self-Assembly

“…This holoCNC surface tension is slightly higher than those of surface modified CNCs, such as poly [2-(dimethylamino)ethyl methacrylate]-grafted-CNCs (47 mN/m) 42 and Jeffaminegrafted oxidized CNCs (41 mN/m), 43 but has the advantage of being from far more efficiently isolated and without additional reactions. Both fluorescence probe and surface tension analysis indicate holoCNCs to be more highly amphiphilic than CNCs, exhibiting surface active behavior by lowering the equilibrium surface tension of water to 49.2 mN/ m and forming aggregates at above CAC of 0.57%.…”

Preparing cationic cotton linter cellulose with high substitution degree by ultrasonic treatment

“…Cellulose nanocrystals (CNCs) have gained increasing attention for cationic modification in the material community. Their unique chemical and mechanical properties, especially large surface area with high accessibility enable high density of substituents, and a variety of functional groups, including pyridinium (Jasmani, Eyley, Wallbridge, & Thielemans, 2013), quaternary amine (Zhu et al, 2014;Rosilo et al, 2014;Zaman, Liu, Xiao, Chibante, & Ni, 2013;Salajková, Berglund, & Zhou, 2012), poly(2-aminoethylmethacrylate), poly[N-(2-aminoethylmethacrylamide)] (Hemraz et al, 2015), poly[2-(dimethylamino)ethyl methacrylate] (Tang et al, 2014), polyamidoamine dendrimer (Tehrani & Basiryan, 2015) and poly(4-vinylpyridine) (Kan, Li, Wijesekera, & Cranston, 2013) have been successfully covalently bonded to CNCs. And the cationic CNCs could found a wide range of applications, such as sorbent (Zhu et al, 2014), biodegradable flocculants (Kan et al, 2013) surface finishing agent (Zaman et al, 2013).…”

Synthetic Strategies for the Fabrication of Cationic Surface-Modified Cellulose Nanocrystals

“…P(DMAEMA) is a weak polyelectrolyte (pKa of ~7.4 at room temperature) and below its pKa, PDMAEMA chains are positively charged due to the protonation of the pendant dimethylamino groups [74]. P(DMAEMA) was grafted onto the surface of CNCs using the free radical polymerization method in the presence of ammonium persulfate as the water-soluble initiator (Scheme 9) [75]. Cationization of the CNCs' surface was demonstrated at pH 3.0 with a zeta potential of +40 mV.…”