Branched Fluorinated Nonionic Y-Shaped Surfactants. Effect of Molecular Geometry on Liquid Crystalline Phase Behavior

Abstract

The synthesis of branched partially fluorinated nonionic Y-shaped surfactants, with the general formula C F nC2N(EmM)2, where C F n denotes fluorinated alkyl chain F(CF2)n with n ) 4-10, C2 is C2H2, and EmM is oligooxyethylene monomethyl ether with m ) 2, 3, and their hydrocarbon analogs Cn+2N(EmM)2 (Cn equals hydrocarbon chain) is described. These surfactants are synthesized to analyze the influence of the fluorinated alkyl chain on the packing effects to amphiphilic layers in a binary surfactant/water system. The lyotropic phase behavior of these surfactants is investigated by polarizing microscopy. The liquid crystalline (LC) phase polymorphism of the fluorinated C F nC2N(E3M)2 surfactants strongly changes with n from hexagonal H1 phase (n ) 6) to lamellar LR phase (n ) 10). In contrast to other Y-shaped hydrocarbon oligooxyethylene surfactants CnG(EmM)2 (where G denotes a glycerol unit) which form only cubic I1 and H1 phases for n ) 12-16 and m ) 3-5, the phase behavior of the C F nC2N(EmM)2 surfactant/water systems shows a remarkable change in the LC phase polymorphism (from H1 to LR phase) with n and m. Compared to hydrocarbon surfactants these results distinctly confirm the influence of more rigid fluorinated alkyl chain on the phase behavior.

Small-angle X-ray scattering (SAXS) study on nonionic fluorinated micelles in aqueous system

“…Like conventional nonionic surfactants such as poly(oxyethylene), perfluorosurfactants also show a rich phase behavior in aqueous solutions [21][22][23][24][25]. These surfactants in aqueous solution show an upper miscibility gap with a lower critical point in the temperature-composition diagram.…”

Phase behavior and preparation of mesoporous silica in aqueous mixtures of fluorinated surfactant and hydrophobic fluorinated polymer

“…Monduzzi et al reported the counterion effect on the phase behavior of perfluropolyether carboxylates in water [12][13][14]. In spite of the growing study of phase behavior of nonionic fluorinated surfactants in water [15][16][17][18][19][20], the incorporation of fluorinated oil into self-organized structures of fluorocarbon surfactant has rarely been considered [21]. Perfluoropolyether (PFPE) oils have been used as lubricants in many industrial applications and possess the main properties of fluorinated surfactants like thermal, chemical, and biological inertness, and low compatibility with aqueous and hydrocarbon based systems.…”

Phase Behavior of Aqueous Mixtures of Some Polyethylene Glycol Decyl Ethers Revealed by DSC and FT-IR Measurements

“…The phase science of the mixture systems of this type of surfactant and water has so far been a problem attracting considerable attention in fundamental colloid science and the practical application of the surfactants (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13). The highly viscous mesomorphic phases is unfavorable to transport the surfactant preparations in the industrial production process.…”

“…Thus, it is of critical importance to avoid the occurrence of the mesomorphic phases in the manufacture of the surfactant preparations. In the theoretical point of view, the potentially possible sequence of the mesophases appearing with the increase in water content in the mixture, I 2 (reversed discontinuous-type cubic)-H 2 (reversed hexagonal)-V 2 (reversed bicontinuoustype cubic)-L ␣ (lamellar)-V 1 (normal bicontinuous-type cubic)-H 1 (normal hexagonal)-I 1 (normal discontinuous-type cubic), has been interpreted in terms of order-disorder transition and shape transition (7,(11)(12)(13). The former is related to the requirement for the arrangement of the surfactant aggregates in the mixture systems arising from the excluded volume effect.…”