物理化学学报 >> 2019, Vol. 35 >> Issue (1): 84-91.doi: 10.3866/PKU.WHXB201712251

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pH和光对复合型乳液拓扑结构的调控

王喆,贾康乐,刘同庆,胡俊文,李学丰,董金凤*()   

  • 收稿日期:2017-11-15 发布日期:2018-06-13
  • 通讯作者: 董金凤 E-mail:jfdong@whu.edu.cn
  • 基金资助:
    国家自然科学基金(21273165);国家自然科学基金(21573164);国家自然科学基金(21773174)

pH and Light Reconfigured Complex Emulsions by Stimuli-Responsive Surfactants

Zhe WANG,Kangle JIA,Tongqing LIU,Junwen HU,Xuefeng LI,Jinfeng DONG*()   

  • Received:2017-11-15 Published:2018-06-13
  • Contact: Jinfeng DONG E-mail:jfdong@whu.edu.cn
  • Supported by:
    the National Natural Science Foundation of China(21273165);the National Natural Science Foundation of China(21573164);the National Natural Science Foundation of China(21773174)

摘要:

本文采取温度诱导相分离法制备了正庚烷-全氟己烷-水(H/F/W)三相复合型乳液,并利用pH和光双重刺激响应型表面活性剂1-[2-(4-癸基偶氮苯-苯氧基)-乙基]-1-二乙烯三胺(C10AZOC2N3)成功实现了对该H/F/W复合型乳液形貌的调控。一方面,随着C10AZOC2N3浓度的增加,H/F/W复合型乳液实现了从H/F/W型双重乳液经Janus乳液到F/H/W型双重乳液的相反转过程。另一方面,基于pH或紫外/蓝光激发有效调控了H/F/W复合型乳液在Janus乳液和F/H/W型双重乳液之间的可逆转换。调控机理可以解释为:pH改变或紫外/蓝光光照引起C10AZOC2N3构型转变,降低了正庚烷/水界面张力,从而调控H/F/W复合型乳液形貌。本工作为双重环境刺激调控复合型乳液形貌提供了一个简便的新方法—仅仅通过引入一个双重刺激响应型表面活性剂。

关键词: 复合型乳液, Janus液滴, pH敏感, 光响应, 形貌调控

Abstract:

Complex emulsions have attracted much attention because of their relevant application in various fields over the past decade. Though complex emulsions with various topologies can be created by adjusting the fraction of selected components during the homogenization processes, it is still a challenge to control the topology of complex emulsion droplets in situ using stimuli-responsive factors such as light, pH, and temperature. In this work, a three-phase complex emulsion of heptane and perfluorohexane (1:1 volume ratio) in an aqueous solution of a fluorosurfactant, F(CF2)x(CH2CH2O)yH (Zonyl FS-300), and a synthesized pH and light dual-responsive surfactant, 1-[2-(4-decylphenylazo-phenoxy)-ethyl]-1-diethylenetriamine (C10AZOC2N3) (both serving as emulsifiers), was prepared using the temperature-induced phase separation method. The topology of the heptane-perfluorohexane-water (H/F/W) three-phase complex emulsion was highly dependent on the concentration of C10AZOC2N3. Light microscopy images showed that phase inversion from H/F/W to F/H/W type double emulsion via Janus emulsion was achieved by gradually increasing the concentration of C10AZOC2N3. It was noticed that interfacial tension between heptane and an aqueous solution containing 0.1% Zonyl FS-300 (mass fraction) decreased from 28.2 to 7.4 mN∙m-1 when the concentration of C10AZOC2N3 was increased to 0.1% (mass fraction). The topology of the complex emulsion droplets is primarily determined by three interfacial tensions at the contact line: the H/W interface (γH), F/W interface (γF), and H/F interface (γHF). The reduction in interfacial tension between heptane and water was the major factor that controlled the topological transition of the complex emulsion. First, it decreases the contact angle between the H/W and H/F interfaces (θH). Second, it increases the contact angle between the F/W and H/F interfaces (θF) simultaneously. Surfactant C10AZOC2N3 is responsive to both pH and light, and therefore, it potentially endows the fabricated complex emulsion with the corresponding stimuli-responses. Experimental results confirmed that the morphologies of complex emulsions can be tuned reversibly between Janus emulsion and F/H/W type double emulsion either by pH variation or UV/blue light irradiation. Interfacial tension measurements between heptane and water show that either protonation variation or trans-cis isomerization of C10AZOC2N3 caused a decrease of about 5 mN∙m-1 in interfacial tension, suggesting that the nature of pH- and light-induced morphological changes of complex emulsion droplets is the same as that induced by the changes in the concentration of C10AZOC2N3. Correspondingly, a mechanism for the stimuli-responsive morphological change of complex emulsion was proposed based on the reduction of interfacial tension between heptane and aqueous solution interface by changing the configuration of C10AZOC2N3 using pH alteration and light irradiation. This work provides a new approach for controlling the morphologies of complex emulsion droplets with an external double stimulus by simply introducing a dual-responsive surfactant.

Key words: Complex emulsion, Janus droplet, pH-sensitive, Photo-response, Morphology control

MSC2000: 

  • O648