Research On Polymer/SiO₂-TiO₂ Hybrid Fiber Materials

Organic/inorganic hybrid materials combine the advantage of the organic materials (rigidity, high thermal stability and unique optical, electric and magnetie properties) and organic materials (toughness, ductility and processability), which is different from the single marerials and conventional composite materials. So the preparation of such organic/inorganic hybrid materials has received great interest. Organic/inorganic hybrid fiber, which has received few researches at home and abroad, is a kind of organic/inorganic hybrid material. The preparation study of hybrid fibers with excellent mechanical, thermal and optical properties is of burgeoning interest. A variety of silicon-titania hybrid fiber materials with different organic substances were prepared by sol-gel method. Moreover, the hybrid and polymerization mechanisms, morphology, structure and properties of hybrid fiber materials were investigated. Main works are as follows:1. Silica sol was prepared by sol-gel method with tetraethoxysilane (TEOS) as the material. The influencing factors on the spinnability of silica sol and the best reaction conditions of the preparation of SiO₂ fibers were studied. The structures and properties of SiO₂ fibers were analyzed by FT-IR, optical microscope and X-ray diffraction. The spinnability of the sol influenced by the molar ratio of H+ and TEOS, the molar ratio of water and TEOS, the kind of the catalyst and the temperature of the reaction. The spinnability of the sol decreased with the increasing temperature. The sol possessed best spinnability when the molar ratio of water and TEOS is 1.5, the molar ratio of H+ and TEOS is 0.03 with HCl as catalyst. The SiO₂ fibers are amorphous fibers. The diameters of the fibers are about 50μm, and the fibers have good transparence and uniformity. This will provide the basis for the preparation of amorphous SiO₂ fibers and the hybrid fiber, which possessing improved thermal and optical properties.2. PMMA/SiO₂ hybrid fibers were prepared with PMMA existing and PBMA/SiO₂ hybrid fibers were prepared via in-situ polymerization with TEOS as material by sol-gel method. The mechanism of the hybrid reaction, the structures and properties of the two hybrid fibers were studied by FT-IR, SEM, TGA and DSC. In the hybrid fibers, polymer was linked with SiO₂ by chemical bonds. The diameters of the two hybrid fibers were about 160μm and 80μm, respectively. A homogeneous and continuous phase was formed between organic and inorganic phases. The hybrid fibers have smooth surface, uniform size and good transparence. They show better resistance to heat than pure polymer. PBMA/SiO₂ hybrid fibers have better flexibility.3. PMMA/SiO₂-TiO₂ and PBMA/SiO₂-TiO₂ hybrid fibers were prepared with TEOS and tetrabutyl titanate (TBT) as precursor by sol-gel and drawing method. The morphology, structure and property of hybrid fibers were studied. Polymer was linked with SiO₂-TiO₂ network by chemical bonds. The diameters of the two SiO₂-TiO₂ hybrid fibers were about 150μm and 50μm, respectively. A homogeneous and continuous phase was formed between organic and inorganic phases. With the increasing content of TiO₂, the Ultraviolet (UV) permeating ratio of the hybrid fibers decreased and the intensity of the fluorescene emission peak increased. With the introducing of titania, the hybrid fibers possess the fluorescene emission property and shield UV radiation effectively, which decrease the aging of the hybrid materials. The result of the study is significant to the research of new optical fiber materials and provide theory basis for SiO₂-TiO₂ hybrid fiber materials. The hybrid fibers show better resistance to heat than pure polymer.4. PBMA/SiO₂ hybrid electrospun fibers were prepared via sol-gel in-situ polymerization and electrospinning method. Polymer was linked with SiO₂ by covalent bond via coupling agent (VTEOS). With the increasing content of polymer, the electrospun product changed from the hybrid fibers with the diameters of about 5μm to gathered smooth and heterogeneous granules. Comparing with pure PBMA, the hybrid fibers possess advantage thermal properties and the thermal decomposition temperature of that rises from 260 to 348℃.PVA/SiO₂-TiO₂ hybrid electrospun fibers were prepared by electrospinning method. PVA was linked with SiO₂-TiO₂ network by inter-molecular hydrogen bonds.The diameters of the electrospun fibers were hundreds nanometer. With the increasing content of SiO₂-TiO₂, the network structure increased; the diameter of the fibers increased gradually; blending and contorting structure existed and even ribbon structure appeared. The effective shielding to UV of nano-titania can decrease the aging of the PVA/SiO₂ hybrid materials. Comparing with pure PVA fibers, the crystallinity of hybrid electrospun fibers is decreased distinctly and the thermal decomposition temperature rises from 230 to 317℃. The stability and hydrophobicity of the hybrid fibers are both improved under different pH values.5. PMMA/TiO₂ hybrid materials, which were well-dispersed with inorganic size of 5nm, were prepared by sol-gel method with MMA and TBT as the main material. Polymer chains were linked with inorganic network by covalent bonds; the dimension of phase microdomain is small, which prevented the separation of the two-phase effectively. The hybrid materials existed in the amorphous form. With the increasing content of TiO₂, the dimension of inorganic phase increased, light transmission declined gradually and the transmission of UV reduced gradually. The effective shielding against ultraviolet rays of nanotitania can slow down the light aging of PMMA. Comparing with pure PMMA, the thermal decomposition temperature of PMMA/TiO₂ hybrid materials rises from 270 to about 300℃. PMMA was modified by nanometer particles and thus the scope of the application of PMMA was widened. This will provide the theoretical basis for the preparation of hybrid materials, which possessing improved optical and thermal properties.