Phase evolution in the alkane–P123–water–TEOS quadru-component system: a feasible route to different complex mesostructured materials

Abstract

Directed by the temperature-induced phase transformation in the alkane (from heptane to dodecane)-P123-water-TEOS quadru-component system, i.e., from a swollen inverse hexagonal phase (H 2 ) to a swollen lamellar phase (L α ) and then to a swollen normal micelles phase (L 1 ), complex silica materials, such as mesoporous nanofibres, multilamellar vesicles (MLVs) and mesocellular foams (MCFs), are constructed.Since the discovery of highly ordered mesoporous silicas, 1 a new era of supermolecular self-assembly of mesoporous materials has begun. Due to their potential industrial applications, the controlled construction of ordered porous silica materials has always been one of the focused issues in this field. Generally, controlling the self-assembly of organic (i.e., surfactant)-inorganic composites was considered to be the key factor in the construction of mesoporous materials. Up to now, various routes have been explored to get structural/morphological variations. Specifically, different reaction compositions and conditions can remarkably alter the self-assembly of inorganic-organic composites, and various mesostructures can then be constructed. 2-6The oil-water-surfactant emulsion systems have been widely studied for their potential applications in oil refineries.7 Emulsion morphology transformation in the oil-water-triblock copolymer systems has been well documented, 8 e.g., different lyotropic liquid crystalline or solution phases have been observed. 8a,bFor oil-water-surfactant systems, although various mesoporous silica materials have been obtained, most of these works were focused on pore size expansion and other aspects of the mesoporous materials. 9-11For instance, a small amount of TMB, acting as a swelling agent, was proven to be effective in the synthesis of ordered large-pore SBA-15. 1c However, when a large amount of TMB was used, due to the relatively strong interaction between aromatics and the copolymer surfactants, 8d highly organized/ordered structures were difficult to maintain, instead, mesocellular foam (MCF) structures often resulted.11 Thus, it seems that a proper interaction between an additional component (besides water and surfactant) and the copolymer surfactant is crucial in constructing highly ordered structures. In our previous studies, it was demonstrated that alkanes with different chain lengths interact differently with the P123 surfactant. 10 Only those of suitable chain length, i.e., ranging from hexane to decane, are good matches to P123 copolymers, and can thus be used to build highly ordered large-pore SBA-15. It is well known that the amphiphilic behavior of triblock copolymers is sensitive to temperature changes, which has been used to control the wall thickness of 1c Therefore, by altering the initial reaction temperature, it is possible to tune the relative affinity of the P123 surfactant, and the phase behavior of the alkane-water-surfactant-TEOS emulsion system. Based on our recent studies, 10b herein, by finely tuning the reaction compositions of the alkane-water-P1...

Swelling‐Agent‐Free Synthesis of Siliceous and Functional Mesocellular Foam‐Like Mesophases by Using a Carboxy‐Terminated Triblock Copolymer

“…[17][18][19][20][21][22] MCF materials are aerogel-like mesostructures with uniform spherical cells three-dimensionally interconnected by ''windows''. [17][18][19][20][21][22][23] Compared to aerogel materials with a wide pore size distribution, MCFs have well-defined cell sizes of 25-50 nm and are synthesized without requiring prolonged gelling time and other tedious procedures (e.g., solvent exchange or supercritical drying). [24,25] Siliceous MCF materials exhibit similar chemical properties to mesoporous silicas, and their post-synthesis surface functionalization has also been demonstrated.…”

Propylsulfonic acid functionalized mesoporous silica catalysts for esterification of fatty acids

“…Different SBA-15 materials exhibit variations in their surface area, pore size and wall thickness, which makes them suitable for different applications [8]. The use of swelling alkane agents, such as hexane and dodecane, in the low temperature synthesis of SBA-15 [9][10][11][12][13][14] yielded materials with pore sizes that varied from 9.7-15.7 nm depending on the alkane chain length [8]. Different morphologies (fiber, platelet, rod and film) of mesoporous silica can be prepared by varying the reaction conditions during their synthesis [15][16][17][18][19][20] or by the addition of KCl or NH4F salts [21][22][23].…”

A Better Understanding of the Formation of Silica Nanococoons

“…6,7 Hierarchical hollow silica spheres, such as those with vertical, 8,9 horizontal, 10,11 random, 12 and three-dimensional (3D) pore channels 13,14 in the shells, as well as multilamellar vesicular structures, attracted many researchers due to their potential applications in catalysis and separation. 3,15,16 Generally, vesicles, 13,15 polymer beads, 17 and emulsion systems 18 were used as the templates to control these hollow structures. Among these structures, the most attractive ones should be the frustule-like hollow silica shells with vertical and 3D pore channels, which might find potential applications in drug release, catalysis, and chromatography.…”