Silicone polymers are organic polymers containing silicon atoms that is an important part of polymer chemistry. The main chain of silicone polymers is composed of Si-O bonds, Si-N bonds or Si-B bonds, while the side chain is composed of silicon atoms connect with other organic groups. Among silicone polymers, polysiloxanes with Si-O bonds have attracted growing interest in the past and present decades and extensively studied for multiple applications in materials science, ranging from sprayable superhydrophobic coating and pressure sensor to skin care.
Figure 1. General structure of silicone polymers
Categories of silicone polymers
According to the structure of the silicone polymers, the common silicone polymers can be devided into the following categories.
The silicone oil, oil polymer with low molecular weight, was prepared by adding of H2O to the mixture of (CH3)2SiCl2 and (CH3)3SiCl. (R/Si > 2)
Figure 2. General structure of silicone oil
The silicone rubber with high molecular weight was synthesized by adding of H2O to the monomer [(CH3)2SiCl2]. (R/Si = 2)
Figure 3. Synthesis of silicone rubber
The siliconeresin was prepared by adding of H2O to the mixture of (CH3)2SiCl2 and CH3SiCl3. (R/Si < 2)
Figure 4. General structure of silicone resin
The silicone polymers are extensively applied to functional materials, chemical engineering and personal care. The main applications of silicone polymers are as follows.
Sprayable superhydrophobic coating
Superhydrophobic coatings are widely used in daily life and industry due to their robust liquid-repellency, enable self-cleaning and oil-water separation. The superhydrophobic paint of supramolecular silicone polymer with high substrate binding, mechanical robustness and damagehealing property was prepared for the first time. The supramolecular silicone polymer can repeatedly recovered topographical defects and surface chemistry by simple thermal treatment due to the dynamic intermolecular crosslinking and chemical reorganization. The paint can be sprayed on solid substrates and assembled into porous films with enhanced water repellency.
Figure 5. The superhydrophobic paint of supramolecular silicone polymer
Luminescent PSE composites
Luminescent elastomers have drawn significant interest because of they widely used in flexible full-color displays, stress sensors, and stimuli-responsive materials. Compared to organic elastomers, silicone-based elastomers exhibit superior heat resistance, electrical insulation, and low surface tension. The luminescent perovskite–silicone elastomers (PSE) composites were prepare by introducing inorganic lead halide perovskite nanocrystals into sulfonecontaining silicone networks that constructed by sulfone-containing silicone copolymers with vinyl side groups (PSMVS) and trimethylolpropane tris(2-mercaptoacetate). The PSE composites display strong green fluorescence and excellent stability.
Figure 6. The process of luminescent PSE composites
Flexible and soft pressure sensors have drawn significant attention due to they are widely used in various fields. A novel flexible pressure sensor with remarkably improved force sensing characteristics was constructed by incorporating ionic liquid into polydimethylsiloxane (PDMS). Keratin as a reinforcing filler is dispersed homogeneously in the PDMS matrix. The ionic pressure sensor have advantages, including outstanding mechanical properties, fast response, wide detection range, and high sensitivity.
Figure 7. The pressure sensor is prepare by PDMS and ionic liquid
The balance between oil and water is important for formulating cosmetic products. Silicone compounds are interesting materials for use in skin care products due to the unique properties of neither oilsoluble nor water-soluble. It is the silicone-based cosmetics lack of solubility in oils and water that form a barrier to excretions from the skin while at the same time repelling water and dirt from external sources.
Figure 8. The application of silicone-based cosmetics in skin care products
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Cao C.; et al. Sprayable superhydrophobic coating with high processibility and rapid damage-healing nature. Chem. Eng. J. 2020, 392(15): 124834-124841.
Cuo M.; et al. Luminescent and robust perovskite–silicone elastomers prepared by light induced thiol–ene reaction. Macromol. Rapid Commun. 2021, DOI: 10.1002/marc.202000606.
Liu X.; et al. Silicone-ionic liquid elastomer composite with keratin as reinforcing agent utilized as pressure sensor. Macromol. Rapid Commun. 2021, DOI: 10.1002/marc.202000602.
O'Lenick A. J.; et al. Silicone polymers in skin care. MRS Bulletin 2007, 32: 801-806.