| Recently, silica-based hybrid materials were attractive due to the distinctive structure and function. A series of hybrid materials were synthesized by sol-gel way such as organically modified siloxanes precursor (Orgasiloxane), periodic mesoporous organosilicas, polysilsesquioxane material and ceramics. During the sol-gel process of Orgasiloxane precursors, the hierarchical supermolecular structures were often formed by the self-assembly of precusors or additive molecules. Under the cooperative action of self-assembly and hydrolysis-condensation reaction, some hybrid materials with unique structure and function were obtained, highly ordered langmuir film, chiral hybrid material, stereoselective catalyst and so on.At present, the research on the self-assembly behavior during sol-gel process mainly includes two parts, self-assembly of precursor molecules and the supermolecular self-assembly structures caused by template action of surfactant molecules. Nevertheless, it is not enough about that self-assembly coming from the intermolecular recognition between additive molecules and precursors in the absence of surfactant. Compared with the aforementioned cases, in the present supermolecular system, there are some weak interreaction forces between additive molecules and precursors, in favor of the further decoration and modification of hybrid materials. Due to the contradiction between the static state of supermolecular structure and continues variability of hydrolysis-condensation reaction, it is more composite for the sol-gel process under self-assembly action through the intermolecular recognition between additive molecules and precursors. The research on their hydrolysis-condensation behavior has important academic value.In the present work, the supermolecular structure is constructed by the interreaction between carboxylic acid and y-amineproplytriethoxylsilane (APTES), with the zwitter salt ion as recognition group. Then it is researched about the effect of supermolecular structure on the hydrolysis-condensation behavior of Orgasiloxane precursors, based on the recognition between additive molecules and precursors. Through choosing the different kinds of carboxylic acid as additive molecules, it was investigated for the effects of structure diversity of additive molecules, such as dualistic structure, ternary structure and chain-length, on the hydrolysis-condensation behavior of Orgasiloxane under self-assembly. The research carried out in this thesis mainly includes three parts:1. Synthesis and research on the hydrolysis-condensation behavior of self-assembly structure based on the intermolecular recognization between oxilic acid and APTES(1) The synthesis of supermolecular self-assembly based on the interreaction between oxilic acid and APTES. A novel plate-shaped crystal, formed by the hydrogen bond between carboxyl group and amine group, was prepared by acid-base reaction of APTES and oxalic acid in the anhydrous ethanol solvent. The composition and morphology of amine salt were characterized by SEM, TGA, EA, FT-IR and XRD, respectively. The results show the amine salt had plate-shaped morphology and lamellar structure. In the amine salt molecules, the mole ratio of APTES and oxilic acid is2:1. The crystal has a hexagonal acute-angle twin structure.(2) The research on the hydrolysis-condensation behavior of self-assembly. Respectively, using the self-assembly and APTES as precursors, the sol-gel reaction were performed and the gel product was characterized. The results show that both the hydrolysis-condensation behavior of precursors and the morphology of gel products were completely different for the APTES and self-assembly crystal. The difference is caused by supermolecular self-assembly structure formed in the presence of oxilic acid. The hydrolysis-condensation product, from the hydrolysis-condensation process of self-assembly, has variegated morphology, but it is irregular topography for the APTES. Under low water/ethanol ratio, in the solid-liquid biphasic system with amine salt as precursor, the spherical chrysanthemum-shape polysilsesquioxane particles were formed. Nevertheless, under high water/ethanol ratio, the precursor amine salt crystal was dissolved in the solution and the smooth microspheres were obtained. It is inferred that the difference of morphology, for hybrid material, was attributed to the cooperative reaction of supramolecular self-assembling and hydrolysis-polycondensation reaction.2. Construction of supermolecular structure from APTES and citric acid and research on the hydrolysis-condensation processIn order to investigate the effect of multiple recognition pattern on the self-assembly behavior of supermolecular system during hydrolysis-condensation, in the ethanol/water system, the sol-gel reaction, with APTES as precursor, was performed in the presence and absence of citric acid, respectively. The sol-gel process was monitored by FT-IR, fluorescence microscope, viscosity analysis, and the structure of products was characterized by SEM, TGA, EA and XRD. Taken together, the results indicated that the presence of citric acid fosters the hydrolysis-condensation reaction of APTES, comprared with pure APTES as precursor, and the short-range ordered spherical particles were obtained. During the sol-gel, the heterogenicity of system was caused by the supermolecular self-assembly between the citric acid and silanol, the hydrolysis product of APTES. There was forming "rich-water domains" in the reaction system. In those "rich-water domains", the needle-like citric acid crystal was fomed and separated from the solution, due to the low solubility. Furthermore, water was consumed by the hydrolysis of precursors, and the relative quantity of ethanol rised in the "rich-water domains", which caused the redissolution of citric acid crystal. Then the emulsion particles were formed with the destruction of self-assembly structure around citric acid crystal. The emulsion particles have shell forming by the supermolecular structure from the citric acid and silanol, and core containing the citric acid solution. With the transmmition of APTES from the system into inner of emulsion particles, the condensation reaction was gradually completed. In the end, the spherical solid particles were obtained.3. Effect of chain-length on supermolecular self-assembly structure based on the intermolecular recognization of outermolecule and precursor(1) The synthesis of supermolecular self-assembly from the interreaction between dicarboxylic acid with different chain-length and APTES. Based on the acid-base reaction between carboxyl group and amine group, the amine salt was synthesized by acid-base reaction of APTES and malonic acid, succinic acid, hexane diacid and decanedioic acid, respectively. The composition and morphology of a series of amine salt were characterized by FT-IR, TGA, EA, SEM and XRD. The results show that the morphology of amine salt transformed from the plate to random bulk solid, with the increasing of chain-length. At the same time, the degree of order of structure declined. In the all amine salt molecules, the mole ratio of the APTES and dicarboxylic acid is2:1.(2) The research on the hydrolysis-condensation behavior of APTES in the presence of dicarboxylic acid with different chain-length. The sol-gel reaction was performed, with APTES as precursor and dicarboxylic acid, malonic acid, succinic acid, hexane diacid and decanedioic acid, as additive molecules, respectively. It was investigated for the effect of chain-length on the hydrolysis-condensation behavior of precursor in the Bola structure molecule. The relative reaction mechanism was proposed. In the presence of short-chain dicarboxylic acid, the hydrolysis rate of APTES was faster, and the condensation is more complete. The gel product were spherical or mesopore hybrid material. However, for the long-chain dicarboxylic acid, hexane diacid and decanedioic acid, the bulk solid material without regular morphology was obtained. It is inferred that the differences of dynamic behavior and aggregate type of precursors are caused by inflexibility of short chain and entanglement of long chain. |
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