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Synthesis and Stability of Water-in-Oil Emulsion Using Partially Reduced Graphene Oxide as a Tailored Surfactant
Langmuir ( IF 3.7 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acs.langmuir.7b02320 Tanesh D. Gamot 1, 2, 3 , Arup Ranjan Bhattacharyya 2 , Tam Sridhar 4 , Fiona Beach 5 , Rico F. Tabor 6 , Mainak Majumder 3
Langmuir ( IF 3.7 ) Pub Date : 2017-09-19 00:00:00 , DOI: 10.1021/acs.langmuir.7b02320 Tanesh D. Gamot 1, 2, 3 , Arup Ranjan Bhattacharyya 2 , Tam Sridhar 4 , Fiona Beach 5 , Rico F. Tabor 6 , Mainak Majumder 3
Affiliation
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Graphene oxide (GO) is widely known as an amphiphile having hydrophilic oxygen functionality and unoxidized graphitic patches as the hydrophobic domains. Exploiting this amphiphilicity, GO serves as a surfactant to stabilize oil–water interfaces. While there are numerous reports on GO as a surfactant, most of these reports concern oil-in-water (O/W) emulsions, and there are very few on the formation of water-in-oil (W/O) emulsions. We prepared W/O emulsions using partially reduced graphene oxide (prGO) as a surfactant. The partial reduction introduces a subtle hydrophilic–lipophilic balance (HLB), which favors the formation of the W/O emulsion. The morphological features and rheological characteristics of the W/O emulsion with 75:25 water-to-oil ratio were investigated and analyzed in detail. The W/O emulsion was found to have polydispersity with wide range of droplet sizes varying between 2 to 500 μm. Using confocal microscopy, the role of parameters such as extent of reduction, continuous phase volume fraction and the concentration of GO on the stability, microstructure and variation of droplet size distribution of the W/O emulsion were carefully monitored. With prGO concentration as large as 0.05% (w/w), highly concentrated emulsion will form, and are stable up to 20 days from formation; destabilization occurred from sedimentation and subsequent coalescence as the partially reduced GO was limited by its dispersion ability in the oil-phase studied here. Understanding the mechanisms behind the transient stability will enable the development of novel emulsion compositions containing GO as a multifunctional additive.
中文翻译：
部分还原氧化石墨烯为定制表面活性剂的油包水乳液的合成及稳定性
氧化石墨烯（GO）是众所周知的具有亲水性氧官能团和未氧化的石墨斑作为疏水域的两亲物。利用这种两亲性，GO可以用作稳定油水界面的表面活性剂。尽管有许多关于GO作为表面活性剂的报道，但大多数报道都涉及水包油（O / W）乳液，而油包水（W / O）乳液的形成却很少。我们使用部分还原的氧化石墨烯（prGO）作为表面活性剂制备了W / O乳液。部分还原会引入微妙的亲水-亲脂平衡（HLB），有利于W / O乳液的形成。对水油比为75:25的W / O乳液的形态特征和流变特性进行了详细的研究和分析。发现该W / O乳液具有多分散性，且液滴尺寸范围在2-500μm之间。使用共聚焦显微镜，仔细监测诸如还原程度，连续相体积分数和GO浓度等参数对W / O乳液的稳定性，微观结构和液滴尺寸分布变化的作用。prGO浓度高达0.05％（w / w）时，会形成高浓度乳液，并在形成后长达20天保持稳定；由于沉积过程中GO的部分还原受到其在油相中的分散能力的限制，因此由于沉积和随后的聚结而发生了失稳。了解瞬态稳定性背后的机理将使开发含有GO作为多功能添加剂的新型乳液组合物成为可能。
更新日期：2017-09-20
中文翻译：
部分还原氧化石墨烯为定制表面活性剂的油包水乳液的合成及稳定性
氧化石墨烯（GO）是众所周知的具有亲水性氧官能团和未氧化的石墨斑作为疏水域的两亲物。利用这种两亲性，GO可以用作稳定油水界面的表面活性剂。尽管有许多关于GO作为表面活性剂的报道，但大多数报道都涉及水包油（O / W）乳液，而油包水（W / O）乳液的形成却很少。我们使用部分还原的氧化石墨烯（prGO）作为表面活性剂制备了W / O乳液。部分还原会引入微妙的亲水-亲脂平衡（HLB），有利于W / O乳液的形成。对水油比为75:25的W / O乳液的形态特征和流变特性进行了详细的研究和分析。发现该W / O乳液具有多分散性，且液滴尺寸范围在2-500μm之间。使用共聚焦显微镜，仔细监测诸如还原程度，连续相体积分数和GO浓度等参数对W / O乳液的稳定性，微观结构和液滴尺寸分布变化的作用。prGO浓度高达0.05％（w / w）时，会形成高浓度乳液，并在形成后长达20天保持稳定；由于沉积过程中GO的部分还原受到其在油相中的分散能力的限制，因此由于沉积和随后的聚结而发生了失稳。了解瞬态稳定性背后的机理将使开发含有GO作为多功能添加剂的新型乳液组合物成为可能。
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