Hypothesis

Pickering emulsions were prepared using wax and silica submicronic particles (650 nm), as a first step towards the synthesis of Janus particles. Surfactants added to silica particles control the emulsion stability and particles arrangement, i.e. their penetration depth into the wax and their ability to form a monolayer. Thus, a systematic study of surfactants is proposed.

Experiments

Zeta potential measurements and sedimentation tests are conducted to evaluate interactions of two cationic (CTAB: hexadecyltrimethylammonium bromide and DDAB: didodecyldimethylammonium bromide) and two polymeric surfactants with silica surface. Surfactants affinity for the wax is estimated by contact angle measurements. Emulsions stability is compared to evaluate the ability of particles to stabilize wax droplets. Through microscopic analyses, the penetration depth into the wax is measured as well as the ability to form a monolayer or multilayers / aggregates.

Findings

All surfactants modify silica surface properties, but only CTAB and DDAB give stable Pickering emulsions. Because of a better affinity for the wax, DDAB presents the best characteristics for Janus particle synthesis, allowing a larger variation of particles penetration depth into the wax.

中文翻译：

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不同表面活性剂对亚微米二氧化硅颗粒稳定的Pickering乳液的影响

假设

作为合成Janus颗粒的第一步，使用蜡和二氧化硅亚微颗粒（650 nm）制备了Pickering乳液。添加到二氧化硅颗粒中的表面活性剂控制乳液稳定性和颗粒排列，即它们在蜡中的渗透深度及其形成单层的能力。因此，提出了对表面活性剂的系统研究。

实验

进行ζ电势测量和沉降测试以评估两种阳离子表面活性剂（CTAB：十六烷基三甲基溴化铵和DDAB：十二烷基二甲基溴化铵）和两种聚合物表面活性剂与二氧化硅表面的相互作用。表面活性剂对蜡的亲和力通过接触角测量来估计。比较乳液稳定性以评估颗粒稳定蜡滴的能力。通过显微镜分析，可以测量到蜡中的渗透深度以及形成单层或多层/聚集体的能力。

发现

所有表面活性剂都会改变二氧化硅的表面性能，但是只有CTAB和DDAB可以提供稳定的Pickering乳液。由于与蜡的亲和性更好，因此DDAB表现出Janus颗粒合成的最佳特性，从而允许较大的颗粒渗透深度进入蜡中。