Nonionic Fluorinated Surfactant: Investigation of Phase Diagram and Preparation of Ordered Mesoporous Materials

Abstract

The behavior of fluorinated surfactant F(CF2)8C2H4(OC2H4)9OH in water solution was investigated, and the preparation ofmesoporous molecular sieves was achieved. A direct micellar phase (L1) and a hexagonal (H1) liquid crystal were found. Small-angle X-ray scattering measurements proved that the hydrophobic chains are completely extended and that the cross sectional area remains constant in H1. At 80 degrees C, materials with a hexagonal array of their channel are prepared via a cooperative templating type mechanism in a wide range of surfactant concentrations (5-20 wt %). Decreasing the hydrothermal temperature leads to the formation ofwormhole-like structure. In this case the channel arrangement is no longer governed by the surfactant behavior but by the silica condensation and polymerization. An increase of the mean pore diameter with heating temperature is noted. This result is associated with changes of aggregation number with temperature. A comparison of the characteristics of the materials obtained with both hydrogenated and fluorinated surfactants is also made.

Cloud point curve of nonionic surfactant related to the structures of mesoporous materials

“…This observation led us to conclude that the CTM mechanism is not favored if the cloud point is too low. This tendency is confirmed by the investigation of the R F 8 (EO) 9 /water system [31], since for this surfactant the value of cloud point is superior to 100 • C and we have demonstrated that without oil well ordered materials can be obtained.…”

“…Taking into account this equivalence rule, we can consider that C 16 (EO) 10 is the hydrogenated analogue of R F 8 (EO) 9 . Indeed, both templates have the same V H /V L ratio equal to 1.4 and lead to well ordered mesoporous materials [15,31]. Therefore, if V H /V L is the main parameter that drives the channel arrangement, using R F 7 (EO) 7 (V H /V L = 1.1) we could expect to form well ordered mesostructures.…”

“…Indeed, the energy of the C-F bond is 552 kJ mol −1 instead of 338 kJ mol −1 for the C-H bond [30]. In order to take benefits of nonionic surfactants, i.e., an easy removal of the template and of fluorinated ones, i.e., high thermal stability, our group develops the preparation of mesoporous materials by using nonionic fluorinated surfactants [31]. Since we have reported the first example of molecular sieves obtained with only fluorinated surfactant, several groups have also prepared by this way mesoporous materials to control their pore diameter [32][33][34][35].…”

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.…”

Synthesis and characterization of wormhole-like mesoporous Ce0.6Zr0.35Y0.05O2 solid solutions

“…The difference in shape suggests a decline in pore regularity. The observed phenomena are characteristics of wormhole-like architectures [4,6,[12][13][14][15] . We found that it is especially so in the cases of the EG-removed CZY precursor and the CZY-3 sample (curves 3 and 4 in Figure 3(a)); the latter case may be related to the partial occupancy of NaCl inside the pores of the CZY precursor.…”