Mechanism of the Influence of Phenyl Groups on the Dielectric Constant
The introduction of phenyl groups (Ph-CH=CH2) significantly alters the dielectric properties of organosilicon materials, mainly through the following mechanisms:

Enhanced electronic polarization: The π electron cloud of the benzene ring is more easily deformed under the action of an external electric field, and this electronic polarization is a key component of the dielectric constant. The introduction of phenyl groups increases the electronic polarizability of the material, thereby increasing the dielectric constant.

Change in dipole moment: The presence of benzene rings in phenyl silicone oil increases the molecular dipole moment, especially when the phenyl content increases, the rigidity of the molecular chain is enhanced, and the ability of dipole orientation polarization is improved.

Steric hindrance effect: The introduction of phenyl groups hinders the movement of molecular chains and limits the orientation polarization of dipoles. This effect partially offsets the enhancement of electronic polarization.

Hydrogen bonding: The Si-OH groups that may exist in phenyl silicone oil can form a hydrogen bond network, and this interfacial polarization also affects the dielectric constant.

Quantitative Relationship between Phenyl Content and Dielectric Constant
Experimental data show a clear quantitative relationship between phenyl content and dielectric constant:

Typical values: The dielectric constant of phenyl silicone oil is approximately 2.7 at room temperature, while the dielectric constant of methyl silicone oil is usually 2.5-2.6.

Influence of content: As the molar fraction of phenyl groups increases, the dielectric constant shows a trend of first increasing and then stabilizing. When the phenyl content reaches a certain proportion (approximately 15-20%), the increase in dielectric constant tends to saturate. Blended System Data:

Phenyl/vinyl blended silicone rubber (PMVQ/MVQ) shows significantly improved dielectric properties when the phenyl silicone rubber content is 15% by weight.
The dielectric constant of trifluoropropyl/vinyl blended silicone rubber (FMVQ/MVQ) is 3.74 (a 40.07% improvement compared to pure vinyl silicone rubber).
Temperature Influence: The dielectric constant of phenyl silicone oil decreases with increasing temperature, and this change is more pronounced than that of methyl silicone oil.

Comparison of Dielectric Properties of Phenyl-Modified Organosilicon with Other Modified Systems
Material Type | Dielectric Constant (1MHz) | Dielectric Loss | Temperature Stability | Application Fields
Phenyl Silicone Oil | 2.7-3.0 | Low | Good | High-frequency electronics, capacitors
MQ Silicone Resin | 2.5-3.2 | Low | Excellent | Electronic packaging
VMQ Silicone Resin | 2.09-2.49 | Low | Good | Sensor packaging
HVQ Silicone Resin | 2.8-3.0 | Low | Excellent | High-voltage insulation
Comparison with MQ Silicone Resin: MQ silicone resin has a three-dimensional network structure and stable dielectric properties (dielectric constant 2.5-3.2), but phenyl-modified silicone oil has better dielectric stability at high temperatures.

Comparison with VMQ Silicone Resin: The dielectric constant of VMQ silicone resin increases with increasing hydroxyl content (from 2.09 to 2.49), but the dielectric properties of phenyl-modified silicone oil are less affected by hydroxyl content.

Comparison with HVQ Silicone Resin: The dielectric properties of HVQ silicone resin are similar to those of phenyl silicone oil (2.8-3.0), but phenyl silicone oil has better high-frequency characteristics.

Applications of Dielectric Properties of Phenyl-Modified Organosilicon
High-frequency electronic applications: The low dielectric loss of phenyl silicone oil (Df < 0.002 at 1MHz) makes it an ideal choice for 5G communication dielectric materials. Power Capacitors: Phenyl silicone oil, used as an insulating impregnant, provides reliable dielectric protection with a dielectric strength of up to 106.87 kV/mm.

High-Temperature Sensors: Phenyl-modified silicone rubber exhibits stable dielectric properties in the range of -50℃ to +250℃, making it suitable for extreme environment applications.

Optical Devices: High phenyl content silicone resins (>20%) achieve a balance between dielectric properties and optical transmittance, making them suitable for optical packaging.

Conclusion
The introduction of phenyl groups significantly increases the dielectric constant of silicone materials (typical value 2.7-3.0) by enhancing electronic polarization and dipole moment. This effect is positively correlated with the phenyl content but exhibits a saturation point. Compared to MQ/VMQ/HVQ systems, phenyl-modified silicones offer the following advantages in dielectric properties: 1) a wide range of adjustable dielectric constants; 2) excellent high-frequency characteristics; and 3) good temperature stability. These characteristics make phenyl-modified silicones an ideal material choice for high-performance applications such as high-frequency electronics and power capacitors. Future research can further explore the nonlinear relationship between phenyl content and dielectric properties, as well as the regulatory mechanisms of multi-component synergistic modification on dielectric properties.