Among the family of organosilicon materials, polysiloxane stands out as the "king" due to its unique structure and excellent performance, with applications ranging from daily chemical products to advanced aerospace technology.

1. Chemical Structure and Basic Properties

Structural Core: The main chain consists of silicon-oxygen bonds (Si-O-Si), with a bond energy of 443.7 kJ/mol, much higher than carbon-carbon bonds (about 346 kJ/mol), resulting in extremely strong main chain stability.

Basic Properties: Ultra-wide temperature stability (-60℃ to 250℃ for long-term use, short-term resistance up to 350℃); combines inorganic rigidity with organic flexibility (silicon-oxygen bond ionization tendency 51%); excellent hydrophobicity (contact angle up to 150°); some types have outstanding oxygen permeability (e.g., polysiloxane for contact lenses with oxygen permeability of 200DK); thermal conductivity can be enhanced after modification (up to 4W/(m・K) after boron nitride filling).

2. Main Application Areas and Their Reasons

Medical and Health: Silicone rubber is used as implant-grade material due to physiological inertness (e.g., breast implants, catheters); silicone hydrogel contact lenses have oxygen permeability more than 6 times that of traditional hydrogels, improving wearing comfort.

Electronics and New Energy: Addition-cured silicone impregnation varnish has 50% higher arc resistance than epoxy resin and can achieve gap-free insulation through vacuum pressure impregnation; thermal conductive silicone gel is used for battery pack heat dissipation, with usage in new energy vehicles three times that of fuel vehicles; polysiloxane side chain modification in solid electrolytes can improve ionic conductivity, potentially solving lithium dendrite issues.

Industry and High-end Manufacturing: Silicone rubber seals withstand extreme temperatures and radiation in spacecraft; methylphenyl silicone resin coatings are used for high-temperature resistant coatings in aircraft engines; silane impregnators extend concrete lifespan to over 50 years; hydrophobic agents on glass curtain walls provide self-cleaning ability.

Daily Chemicals and Consumer Products: Polydimethylsiloxane (PDMS) accounts for over 90% of the global hair care market, giving hair a smooth feel; silicone microspheres in cosmetics provide light scattering effects, creating a matte finish.

3. Reasons for Being the Organosilicon "King"

Performance Advantages: Diverse and comprehensive performance, covering temperature stability, hydrophobicity, etc., with precise performance tuning possible by introducing side groups, enabling wide application range.

Market Position: In 2023, the global market size reached 21.4 billion USD, with over 5,000 products; China's production capacity accounts for 60% of the global total, with an output of 1.27 million tons; the market size is expected to exceed 15.4 billion USD by 2030, with a compound annual growth rate of 3.7%; the industry is characterized by "one dominant and many strong players," with Chinese companies gradually achieving domestic substitution of high-end products (e.g., Xingfa Group breaking the monopoly on electronic-grade silicone oil).

4. Synthesis Methods and Material Modification

Synthesis Methods: Mainly condensation reactions (organosilicon alcohols/chlorosilanes condense under catalysts, releasing small molecules) and ring-opening polymerization (cyclic siloxane monomers polymerize under catalysts); recently, biocatalysis and photo-induced radical polymerization technologies have increased in use (the former has over 90% atom utilization, reducing wastewater; the latter enables rapid room temperature preparation, suitable for 3D printing).

Material Modification: Introduction of side groups (e.g., phenyl groups improve high-temperature resistance and refractive index, vinyl groups increase reactivity); filler modification (boron nitride, carbon nanotubes, etc., improve thermal conductivity and mechanical properties).

5. Environmental Friendliness and Sustainability

Environmental Challenges: Cyclic methylsiloxanes (D4, D5) are persistent and bioaccumulative, regulated by the EU; silicone oil degrades slowly in nature.

Countermeasures: Green production (e.g., Dow Corning optimizing processes to reduce emissions); circular economy (bio-based polysiloxanes are degradable, waste silicone rubber depolymerization recycling rate exceeds 95%); policy promotion (EU restricts D4 and D5 use in cosmetics by 2026, China guides enterprises to use low VOC processes).

6. Development History and Future Trends

Development History: Laboratory research in the early 20th century, industrial production after the 1940s, followed by synthesis method optimization, performance improvement, and expanded application scope.

Future Trends: Material performance upgrades (e.g., self-healing dynamic cross-linked silicone rubber, photo-responsive polysiloxane); expansion of application scenarios (mass production of silicon-based anode materials, degradable nanocomposite elastomers for flexible electronics).

7. Challenges and Limitations

Technology: Some high-end product manufacturing technologies are monopolized abroad, and domestic substitution requires time.

Environment: Some products have poor biodegradability, with potential environmental impacts to be addressed.

Cost: Synthesis processes for special performance products are complex and costly, limiting large-scale application.

Regulations Environmental regulations are becoming stricter, requiring companies to invest more funds and technology to meet requirements.