Thermally and pH-responsive gelation of nanoemulsions stabilized by weak acid surfactants
Thermally and pH-responsive gelation of nanoemulsions stabilized by weak acid surfactants
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DOI：
10.1016/j.jcis.2019.12.054
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发表时间：
2020-03-15
影响因子：
9.9
通讯作者：
Doyle, Patrick S.
中科院分区：
文献类型：
--
作者：
Cheng, Li-Chiun;Hashemnejad, Seyed Meysam;Doyle, Patrick S.
纳米乳液广泛用于食品、药物成分和化妆品等应用。此外，纳米乳液由于其易于合成和配方的灵活性而一直是模型胶体系统，这使得人们能够设计液滴间电位，从而合理地调节材料的微观结构和流变特性。在这篇文章中，我们研究了一种纳米乳液系统，其中液滴间的相互作用是由温度和pH值调制的。我们开发了一种纳米乳液悬浮液，其中液滴是由弱酸表面活性剂稳定的，其带电状态可以独立控制温度和pH值，导致响应的静电排斥。此外，表面活性剂上的额外的聚（乙二醇）链段（PEG）通过PEG-PEG缔合和离子偶极相互作用引起液滴之间的温度响应性吸引。这三种相互作用的相互作用引起材料性质和结构随温度变化的非单调趋势。导致这些趋势的潜在机制是通过仔细表征纳米乳液液滴和研究分子相互作用来获得的。这种机理理解还提供了使用pH和离子强度调节液滴间电位的指导。此外，分子的弱酸性表面活性剂的理解也揭示了由pH值的开关触发的纳米乳液液滴的不稳定。使用外部刺激的吸引力和排斥力的相互作用的竞争的控制开辟了设计复杂的基于纳米乳液的软材料的可能性可控的结构和流变性能。(C)2019爱思唯尔公司All rights reserved.
Nanoemulsions are widely used in applications such as in food products, pharmaceutical ingredients and cosmetics. Moreover, nanoemulsions have been a model colloidal system due to their ease of synthesis and the flexibility in formulations that allows one to engineer the inter-droplet potentials and thus to rationally tune the material microstructures and rheological properties. In this article, we study a nanoemulsion system in which the inter-droplet interactions are modulated by temperature and pH. We develop a nanoemulsion suspension in which the droplets are stabilized by weak acid surfactants whose charged state can be independently controlled by temperature and pH, leading to a responsive electrostatic repulsion. Moreover, the additional poly(ethylene glycol) segment (PEG) on the surfactant gives rise to a temperature responsive attraction between droplets via PEG-PEG association and iondipole interaction. The interplay of these three interactions gives rise to non-monotonic trends in material properties and structures as a function of temperature. The underlying mechanism resulting in these trends is obtained by carefully characterizing the nanoemulsion droplets and studying the molecular interactions. Such mechanistic understanding also provides guidance to modulate the inter-droplet potential using pH and ionic strength. Moreover, the molecular understanding of the weak acid surfactant also sheds light on the destabilization of the nanoemulsion droplets triggered by a switch in pH. The control of the competition of attractive and repulsive interactions using external stimuli opens up the possibility to design complex nanoemulsion-based soft materials with controllable structures and rheological properties. (C) 2019 Elsevier Inc. All rights reserved.