Synthesis and Surface Properties of CO₂H Type Gemini Surfactant Having Semifluoroalkyl Group as Hydrophobic Group

Abstract

Novel CO2H type gemini surfactants having semifluoroalkyl group (Rf-(CH2)n-: Rf = C4F9, C6F13, C8F17 and n = 2, 3) as hydrophobic group were successfully synthesized and their surface properties were studied. (Perfluoroalkyl)ethylmalonic esters were synthesized by the reaction of malonic ester with Rf(CH2)2I using NaH as base in THF/DMF. (Perfluoroalkyl)propylmalonic esters were synthesized from allylmalonic ester, namely by the radical addition of Rf-I using AIBN as initiator, and reduction with Zn/AcOH. Those fluoroalkylated malonic esters were connected using Br(CH2)sBr (s = 3, 4) to give dimeric tetraesters. Then, tetraesters were hydrolyzed using KOH/EtOH followed by decarboxylation in AcOH to afford CO2H type gemini surfactants. To study their surface properties, both surface tension-concentration and surface pressure-area isotherms were measured. As expected, COOH geminis showed one order of magnitude lower critical micellar concentrations (CMC) than that of conventional 1+1 type surfactant. In the surface pressure-area measurements, as length of fluoroalkyl increased, lift-off area (AL) decreased, monolayers were clearly formed upon compression and the limited areas (A∞) for C6F13 and C8F17 were smaller than twice of that of C8F17(CH2)2COOH. Especially, COOH geminis having Rf = C8F17 and -(CH2)3- spacer showed the formation of solid phase monolayers, and the planar five membered ring-like structure was proposed.

Novel Fluorinated Gemini Surfactants with γ-Butyrolactone Segments

“…In fluoroalkylated gemini surfactants, fluoroalkyl groups are introduced into the tail segment; this is generally achieved by radical addition of a perfluoroalkyl iodide to a H 2 C CH-group, as described by Brace 17 . In our previous study 14 , CO 2 H-type malonic acidbased gemini surfactants containing semifluoroalkyl groups Rf-CH 2 n -; Rf C 4 F 9 , C 6 F 13 , C 8 F 17 and n 2, 3 and -CH 2 s -spacers s 3, 4 were successfully synthesized via the connection of Rf-CH 2 3 -malonic esters, which were synthesized by radical addition of Rf-I to the H 2 C CH-CH 2 -moiety of allylmalonic ester, followed by reduction with Zn/AcOH, linking with Br CH 2 s Br s 3, 4 to tetraesters, and then hydrolysis and decarboxylation. In this synthetic route, the introduction of the fluoroalkyl group into the tail segment is the initial step.…”

“…Similar to the synthesis of malonic acid-based gemini compounds 14 , dilactone diesters 7 were hydrolyzed under alkaline conditions using excess KOH; after acidification, the precipitates were collected. The IR spectra showed that the products were mixtures of butyrolactones and γ-hydroxybutyric acids.…”

“…based gemini surfactants Rf-CH 2 n -; Rf C 4 F 9 , C 6 F 13 , C 8 F 17 and n 2,3 14 , and their surface properties were studied. Surface tension measurements confirmed the superiority of the surfactant properties of the gemini structure, and it was concluded that the gemini structure would be excellent at achieving low surface tension, even with a fluoroalkyl chain length of C5 or below.…”

Study of the zinc action on the 2-chloroethyl 2-bromo-2-perfluoroalkylethanoates

“…The prolonged heat of the same reagents 2 with a zinc excess, yield the bis(vinyl perfluoroalkyl) oxyethylene 6 as exclusive products. The highly fluorinated obtained compounds 2-perfluoroalkyl acids 3 and bis(vinyl perfluoroalkyl ester) ethoxides 6, among many others applications, may have interesting surface properties [64][65][66] and can also undergo some interesting reactions, particularly in the synthesis of organofluorinated heterocyclic compounds [67,68] …”

“…Such compounds are used as surfactants [17][18][19][20], agrochemicals [21,22], pharmaceutical [23][24][25][26][27], biological [28] and medical agents [29,30]. While they are detected in human bodies [31,32], municipal water and solid wastes in different industrial areas around the world [33][34][35] and considered as high polluter for environment and toxic compounds [36,37], perfluoroalkyl acids are interesting compounds used as tensioactifs [38][39][40], fire-fighting foam [41][42][43], fluoropolymers [44] and other important applications.…”