Effect of Thermal History and Hydrocarbon Core Size on Perfluorocarbon Endoskeletal Droplet Vaporization.
Effect of Thermal History and Hydrocarbon Core Size on Perfluorocarbon Endoskeletal Droplet Vaporization.
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DOI：
10.1021/acs.langmuir.1c03350
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
Gazendra Shakya;A. K. Fajrial;Xiaoyun Ding;Mark A Borden
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作者：
Gazendra Shakya;A. K. Fajrial;Xiaoyun Ding;Mark A Borden
可蒸发氟碳碳氢化合物内骨骼液滴是一种独特的相变乳状液，具有有趣的物理和热力学特征。在这里，我们展示了复合固体n-C20H42或n-C21H44和液体n-C5F12液滴的各种形态的微流控制备，如固-液、液-固和Janus类型。此外，我们还研究了这些内骨骼液滴的汽化行为，重点研究了热处理和核心尺寸的影响。汽化和差示扫描量热结果的比较表明，对于C20H42/C5F10液滴，汽化发生在体相碳氢化合物熔化之前，而对于C21H44/C5F10液滴，汽化发生在转子相附近。我们发现，对液滴进行热处理增加了蒸发液滴的比例，也提高了液滴的蒸发温度，尽管这种影响是暂时的。此外，我们还发现，改变固体碳氢化合物核心相对于周围液体壳层的相对尺寸会增加汽化温度和汽化分数。综上所述，这些数据支持这样的假设，即直链烷烃表现出的表面熔融行为可能触发了氟碳挥发事件。这些结果可能有助于理解界面热力学和传输，以及设计用于生物医学成像和其他应用的新型可汽化内骨骼液滴。
Vaporizable hydrocarbon-in-fluorocarbon endoskeletal droplets are a unique category of phase-change emulsions with interesting physical and thermodynamic features. Here, we show microfluidic fabrication of various morphologies, such as solid-in-liquid, liquid-in-solid, and Janus-type, of complex solid n-C20H42 or n-C21H44 and liquid n-C5F12 droplets. Furthermore, we investigated the vaporization behavior of these endoskeletal droplets, focusing on the effects of heat treatment and core size. Comparison of vaporization and differential scanning calorimetry results indicated that vaporization occurs prior to melting of the bulk hydrocarbon phase for C20H42/C5F10 droplets and near the rotator phase for C21H44/C5F10 droplets. We found that heat treatment of the droplets increased the fraction of droplets that vaporized and also increased the vaporization temperature of the droplets, although the effect was temporary. Furthermore, we found that changing the relative size of the solid hydrocarbon core compared to the surrounding liquid shell increased the vaporization temperature and the vaporizing fraction. Taken together, these data support the hypothesis that surface melting behavior exhibited by the linear alkane may trigger the fluorocarbon vaporization event. These results may aid in the understanding of the interfacial thermodynamics and transport and the engineering of novel vaporizable endoskeletal droplets for biomedical imaging and other applications.