摘要
利用季铵化木质素与TiO2纳米颗粒复合作为乳化剂,以正癸烷为油相,制备具有pH响应性的O/W型Pickering乳液.该乳液在6.0 <pH <7.0范围内稳定,在酸性和碱性条件下不稳定.在中性溶液中,季铵化木质素带负电,TiO_2带正电,两者通过静电吸附作用结合,季铵化木质素的疏水性苯丙烷骨架使TiO_2的亲水性降低,提高颗粒的界面活性,形成稳定的乳液.在酸性和碱性条件下,季铵化木质素和TiO_2带同种电荷,两者之间存在强烈的静电斥力,而单独的TiO_2纳米颗粒亲水性太高,无法稳定于油水界面形成稳定的乳液,故乳液破乳.因此季铵化木质素与TiO_2纳米颗粒之间的吸附特征赋予Pickering乳液双重pH响应特性,向体系中加入HCl溶液以及NaOH溶液改变水相的pH值,能使乳液体系在乳化与破乳状态之间循环多次,同时乳滴没有明显的变化,具有优异的耐盐性.
pH-Responsive oil-in-water Pickering emulsions using n-decane as oil phase were prepared by mixing quaternized lignin (QAL) and titanium dioxide (TiO2) nanoparticles as emulsifiers. The emulsions stabilized by 0.5 wt% TiO2 neat nanoparticles are extremely unstable due to the strong hydrophilic properties of the nanoparticles. However, when TiO2 nanoparticles are dispersed in neutral solution containing 0.1 wt% QAL, all the emulsifier particles can be applied onto the n-decane/water interface, which greatly improves the stability of the emulsions and the droplet size ranges from 20 μm to 60 μm. Meanwhile, emulsions stabilized by QAL and TiO2 nanoparticles show outstanding pH-responsive properties, which are stable in the range of 6.0 < pH < 7.0 while unstable under the acidic and basic conditions. The synergistic stabilization mechanism of QAL and TiO2 nanoparticles was studied with zeta potential, adsorption kinetics, and three-phase contact angle. QAL pertains to amphoteric surfactants whose isoelectric point is 7.5. When 6.0 < pH < 7.0, QAL molecules are negatively charged, allowing them to combine with TiO2 nanoparticles via electrostatic interactions. The hydrophobic phenylpropane skeleton of QAL molecule reduces the hydrophilicity of TiO2 nanoparticles thereby enhances their surface activity to form stable emulsions. However, under the acidic and alkaline conditions, QAL molecules turn into the same charge with TiO2 nanoparticles. Thus, QAL molecules significantly desorb from TiO2 nanoparticles surface due to electrostatic repulsion. TiO2 nanoparticles become intensely hydrophilic again and unable to stay on the oil/water interface, which makes the emulsions unstable as a result. Therefore, the adsorption behaviour between QAL and TiO2 nanoparticles endows Pickering emulsions with double pH-responsive characteristics. With the alternative pH of aqueous phase by adding aqueous HCl and aqueous NaOH, the emulsion system can be recycled many times between emulsification and demulsification while the average dr
作者
卢烁
杨东杰
李圆圆
李致贤
邱学青
Shuo Lu;Dong-jie Yang;Yuan-yuan Li;Zhi-xian Li;Xue-qing Qiu(State Key Laboratory of Pulp and Paper Engineering, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640;College of Pharmacy, Henan University of Chinese Medicine, Zhengzhou 450046)
出处
《高分子学报》
SCIE
CAS
CSCD
北大核心
2019年第2期160-169,I0004,共11页
Acta Polymerica Sinica
基金
国家自然科学基金(基金号21878114
21436004)
广东省科技计划项目(项目号 2017B090903003)
广州市科技计划项目(项目号 201707020025)资助
