Ardyani Tretya, Mohamed Azmi, Abu Bakar Suriani, Sagisaka Masanobu, Hafiz Mamat Mohamad, Khairul Ahmad Mohd, Ibrahim Sofian, Abdul Khalil H P S, King Stephen M, Rogers Sarah E, Eastoe Julian
Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjong Malim, Perak, Malaysia.
Department of Chemistry, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjong Malim, Perak, Malaysia; Nanotechnology Research Centre, Faculty of Science and Mathematics, Universiti Pendidikan Sultan Idris, 35900 Tanjong Malim, Perak, Malaysia.
J Colloid Interface Sci. 2022 Aug 15;620:346-355. doi: 10.1016/j.jcis.2022.03.145. Epub 2022 Apr 2.
As compared to common aliphatic surfactants, increasing the number of pendant or incorporated aromatic groups in a surfactant is expected to offer significant enhancement in the affinity for graphene surfaces. The basis for enhanced graphene-philicity of aromatic surfactants is that they can develop appreciable π - π interactions with graphene. Furthermore, charged (anionic) surfactants are expected to confer electrostatic stabilization on surfactant-graphene composites. Hence, it is expected that anionic aromatic surfactants combine these two properties for effective stabilization of graphene dispersions in water.
The properties of two custom made graphene-compatible surfactants carrying two and three aromatic moieties in the hydrophobic tails, namely DC3Ph2 (sodium 1,4-dioxo-1,4-bis(3-phenylpropoxy)butane-2-sulfonate) and TC3Ph3 (sodium 1,5-dioxo-1,5-bis(3-phenylpropoxy)-3-((3-phenylpropoxy)carbonyl) pentane-2-sulfonate) were compared with other common ionic commercial surfactants. Air-water (a/w) surface tension measurements were used to assess the surfactant adsorption and interfacial packing in the absence and presence of graphene. The surfactant coverage index for graphene (Ф) was calculated using surfactant headgroup areas derived from a/w surface tension data, chain volumes, and molecular fragment volumes from literature.
Increasing the number of aromatic groups and tails per surfactant was shown to increase the ability of surfactants to pack and fill space, as expressed by Ф. Comparison between the values of Ф for surfactants of different chain structure and architecture showed that the affinity for graphene increased with Ф. Hence, there is an implicit link between surfactant-graphene compatibility and the identity, chemical composition and architecture of the surfactant chains.
与普通脂肪族表面活性剂相比，增加表面活性剂中侧链或所含芳香基团的数量有望显著增强其对石墨烯表面的亲和力。芳香族表面活性剂亲石墨烯性增强的依据是它们能与石墨烯形成可观的π-π相互作用。此外，带电（阴离子）表面活性剂有望赋予表面活性剂-石墨烯复合材料静电稳定性。因此，预计阴离子芳香族表面活性剂兼具这两种特性，可有效稳定石墨烯在水中的分散体。
将两种定制的、疏水尾部分别带有两个和三个芳香基团的与石墨烯相容的表面活性剂，即DC3Ph2（1,4-二氧代-1,4-双（3-苯氧基丙氧基）丁烷-2-磺酸钠）和TC3Ph3（1,5-二氧代-1,5-双（3-苯氧基丙氧基）-3-（（3-苯氧基丙氧基）羰基）戊烷-2-磺酸钠）的性能与其他常见的离子型商业表面活性剂进行了比较。利用空气-水（a/w）表面张力测量来评估在有无石墨烯存在的情况下表面活性剂的吸附和界面堆积情况。石墨烯的表面活性剂覆盖指数（Ф）是根据从a/w表面张力数据得出的表面活性剂头基面积、链体积以及文献中的分子片段体积计算得出的。
结果表明，增加每个表面活性剂的芳香基团和尾链数量会提高表面活性剂的堆积和填充空间的能力，这由Ф表示。不同链结构和架构的表面活性剂的Ф值比较表明，对石墨烯的亲和力随Ф增加。因此，表面活性剂-石墨烯的相容性与表面活性剂链的特性、化学组成和架构之间存在内在联系。
