Wetting solution

A typical wetting solution molecule consists of a hydrophilic head and long hydrophobic tail. (From top to bottom: non-ionic, anionic, cationic and zwitterionic.)

Wetting solutions are liquids containing active chemical compounds that minimise the distance between two immiscible phases by lowering the surface tension to induce optimal spreading. The two phases, known as an interface, can be classified into five categories, namely, solid-solid, solid-liquid, solid-gas, liquid-liquid and liquid-gas.[1]

Although wetting solutions have a long history of acting as detergents for four thousand plus years, the fundamental chemical mechanism was not fully discovered until 1913 by the pioneer McBain.[2][3] Since then, diverse studies have been conducted to reveal the underlying mechanism of micelle formation and working principle of wetting solutions, broadening the area of applications.  

The addition of wetting solution to an aqueous droplet leads to the formation of a thin film due to its intrinsic spreading property. This property favours the formation of micelles which are specific chemical structures consisting of a cluster of surfactant molecules that has a hydrophobic core and a hydrophilic surface that can lower the surface tension between two different phases.[4]

In addition, wetting solutions can be further divided into four classes; non-ionic, anionic, cationic and zwitterionic.[5]

The spreading property may be examined by adding a drop of the liquid onto an oily surface. If the liquid is not a wetting solution, the droplet will remain intact. If the liquid is a wetting solution, the droplet will spread uniformly on the oily surface because the formation of the micelles lowers the surface tension of the liquid.[6]

Wetting solutions can be applied in pharmaceuticals,[7] cosmetics[8] and agriculture.[9] Albeit a number of practical uses of wetting solutions, the presence of wetting solution can be a hindrance to water purification in industrial membrane distillation.[10]

  1. ^ Kronberg, Bengt; Holmberg, Krister; Lindman, Björn (2014-10-31). Surface Chemistry of Surfactants and Polymers. doi:10.1002/9781118695968. ISBN 9781118695968.
  2. ^ Butler, Hilda (2001). Poucher's Perfumes, Cosmetics and Soaps : Volume 3 Cosmetics. Springer Netherlands. ISBN 978-94-011-1482-0. OCLC 958540716.
  3. ^ The Chairman; Ostwald, Wolfgang (1913). "Colloids and their viscosity. A general discussion". Transactions of the Faraday Society. 9: 34. doi:10.1039/tf9130900034. ISSN 0014-7672.
  4. ^ Cui, Xiaohong; Mao, Shizhen; Liu, Maili; Yuan, Hanzhen; Du, Youru (2008-10-07). "Mechanism of Surfactant Micelle Formation". Langmuir. 24 (19): 10771–10775. doi:10.1021/la801705y. ISSN 0743-7463. PMID 18729337.
  5. ^ Glass, Beverley (2016-10-01). "Book review: Physicochemical Principles of Pharmacy: In Manufacture, Formulation and Clinical Use. 6th ed". Australian Prescriber. 39 (5): 178. doi:10.18773/austprescr.2016.065. ISSN 1839-3942. PMC 5079779.
  6. ^ "Wetting Agents". Chemistry LibreTexts. 2013-10-02. Retrieved 2022-04-02.
  7. ^ Ibrahim, Shaimaa S. (June 2019). "The Role of Surface Active Agents in Ophthalmic Drug Delivery: A Comprehensive Review". Journal of Pharmaceutical Sciences. 108 (6): 1923–1933. doi:10.1016/j.xphs.2019.01.016. ISSN 0022-3549. PMID 30684539. S2CID 59291264.
  8. ^ Cite error: The named reference :2 was invoked but never defined (see the help page).
  9. ^ Sunkad, Gayatri (2020). "The importance of agriculture in present world". doi:10.13140/RG.2.2.14008.78080. {{cite journal}}: Cite journal requires |journal= (help)
  10. ^ Cite error: The named reference :7 was invoked but never defined (see the help page).