Introducing SiO2 into the polymer, the prepared nanocomposite exhibits excellent mechanical properties, thermal properties, optics, and electricity. In addition, SiO2 and polymers can produce synergistic effects to endow composite materials with new properties, thus having great potential in the direction of multifunctional materials.
1. Coatings and Coatings
The polymer has good film-forming properties, and the addition of SiO2 endows it with excellent thermal stability and mechanical properties. In addition, high-performance and multifunctional coatings can be prepared by different processes.
Park et al. sprayed hydrophobic SiO2 on the surface of polyurethane (PU)-acrylate (PUA) film to prepare a superhydrophobic coating for roll-to-roll or roll-to-plate systems, with a contact angle of 150° and high light transmittance, suitable for in continuous production. In addition, the PDMS substrate pattern can also be transferred to the PU-PUA film using an ultraviolet irradiation system.
SiO2 has high thermal stability and can be used to prepare flame retardant composite materials. Jiang et al. used hollow mesoporous SiO2 (HM-SiO2), chitosan (CS) and phosphorylated cellulose (PCL) as raw materials, and introduced them into epoxy resin (EP) through a layer-by-layer self-assembly method to prepare an environmentally friendly type flame retardant. The results show that HM-SiO2 contains Si, P, S and other flame retardant elements, which synergize with CS and PCL to endow EP with excellent flame retardant properties. The flame retardant material will form a dense carbon layer on the surface of EP after combustion, which physically blocks the contact of oxygen and combustibles, the flow of composite materials in the interior, and the transfer of heat. According to this idea, multifunctional nanocomposites such as the combination of superhydrophobicity and flame retardant can be prepared.
In the same way, the SiO2 loaded with corrosion inhibitor is used as the filler coating to adhere to the metal surface, which can shield the influence of corrosion factors caused by the external environment. When the coating is defective, the corrosion inhibitor is released to the corresponding position for cross-linking to complete the repair. Shchukina et al. used mesoporous SiO2 as a nano-container, loaded the corrosion inhibitor 8-hydroxyquinoline, and added it to the polyepoxy coating. The results show that when the article is corroded, the pH value around the coating changes, and the slow-release agent in SiO2 begins to dissolve and release to the corresponding position. Only 2% of the corrosion inhibitor can play a good effect. .
2. Biomedicine
SiO2 is non-toxic to cells and has good biocompatibility. It is often used in drug release control, targeted therapy, and detection in the field of biomedicine.
Compared with other porous materials, the pore size of SiO2 can be adjusted and the operation is simple, which provides more space for the design of the carrier structure for sustained drug release. POPOVA et al. loaded sulfadiazine into amino-functionalized spherical MCM-41 and nanoscale SBA-15SiO2 by wet impregnation method, respectively, and modified them with two different polyacrylic resins as a drug-loaded composite system. The results showed that the drug release rate of the nanocomposite drug-loading system was lower than that of unmodified SiO2, no drug was released when the pH value was 1.2, and the loaded drug was successfully released at the target site when the pH value was 6.8. This is attributed to being very sensitive to pH value, and the 2-layer polymer wrapped outside can cooperate with SiO2 to further slow down the rate of drug release.
Timin et al. polymerized the magnetized SiO2 with the polymer guanidine, and used a novel bilirubin-induced fluorescent protein UnaG functional modification to prepare a composite material. When bilirubin was detected in the solution, the composite particles could emit fluorescence, which is used for liver function. clinical diagnosis.
General medical imaging is based on magnetic resonance imaging. Li et al. wrap a layer of SiO2 inorganic shell doped with iron oxide outside the drug polymer with microporous structure. The drug-loading system has good biocompatibility. When the pH value is 7.4, the membrane channel shows an ultra-low drug release rate, which prevents damage to normal cells and basically does not produce side effects. With the increase of acidity, the drug-loaded system reaches the cancer cell target under the magnetic targeting effect, the iron oxide on the inorganic shell is dissolved, the pores of the shell are opened and the drug is released until the inorganic shell is broken; these results show that the drug-loaded system Targeted therapy in vivo was achieved, while showing good in vitro magnetic resonance imaging capability to observe the area of drug release.
3. Environment
The contribution of SiO2 nanocomposites to the environment is mainly reflected in the adsorption of heavy metals. SiO2 has the characteristics of high specific surface area and strong adsorption performance, but the functional group is single, so functionalizing SiO2 is a feasible way to expand the scope of application.
Using the Cu2+ aqueous solution as a model, Plohl et al. prepared a magnetic nano-SiO2 particle (MNPs) adsorbent with a core-shell structure, and discussed the adsorption mechanism of the adsorbent on Cu2+. It was found that the maximum adsorption capacity of the adsorbent for Cu2+ was 143 mg/g, and it could be recycled. Among them, NH/NH2 provides electrons in the adsorption behavior, which reduces the valence state of Cu2+. This type of adsorbent is very suitable for the environmental conditions of sludge, and has the characteristics of high efficiency and environmental protection. The flexible use of different polymers to modify SiO2 can specifically improve the adsorption of SiO2 composites to certain types of heavy metals.
SiO2 composite membrane also has an important position in the field of oil-water separation. By using hydrophilic oleophobic (or lipophilic and hydrophobic) SiO2 to improve the adsorption and dissolution of water (or oil) molecules by the membrane, to hinder oil (or water) molecules Through the membrane, oil and water separation is achieved. The separation efficiency is related to the pore size of the membrane material. Cao et al. sprayed the modified polyurethane and hydrophobic SiO2 on the copper mesh to simply prepare a high temperature (near 100 °C) oil-water separation membrane for the separation of oil substances. The results show that the copper mesh has a high separation efficiency for kerosene, up to 99.3%, and still maintains a good oil-water separation effect after dozens of cycles.
4. Packaging
SiO2/polymer nanocomposites can enhance the barrier properties of traditional packaging in the form of coatings, or use themselves as packaging materials, especially with outstanding performance in water vapor barrier, which is undoubtedly beneficial to food preservation. In order to improve the shortcomings of traditional wrapping paper that are sensitive to gas, moisture and steam, Ibrahim et al. used the prepared polystyrene (PS)/SiO2 to roughen the surface fibers of wrapping paper. The results show that the waterproof performance of the packaging paper is the best when the mass fraction of SiO2 is 4%, and the mechanical properties are improved and the moisture content is decreased. The ultra-thin hydrophobic coating is deposited on the fiber matrix, which blocks pores and pores on the one hand, and acts as a barrier on the surface to prevent the fibers from contacting water molecules, thus making the wrapping paper hydrophobic.
Beatriz et al. developed an active packaging film with mesoporous SiO2 (MCM-41) as an encapsulation container for eugenol and introduced poly(3-hydroxybutyrate-co-3-hydroxyvalerate) by electrospinning ) (PHBV). The results show that the heat resistance, mechanical strength and barrier properties of the film to limonene and water vapor are all improved, and it has long-term antibacterial properties. At this time, SiO2 is not only used as a filler to enhance the performance of the film, but also as a container to reduce the release of bacteriostatic agents in the film, prolong the shelf life and protect the safety of food.
SiO2 itself is non-toxic and tasteless, which can make up for the deficiencies of environmental-friendly packaging in terms of physical and chemical properties and meet the requirements of sustainable development. Horst et al. prepared SiO2-doped degradable starch films by a sol-gel method, and the results showed that the mechanical properties, optical properties and barrier properties of such inorganic-organic hybrid films were enhanced, although the methods used still need to be improved. , but also showed the development potential of SiO2 in hard degradable packaging materials.