Silicones: Preparation and Uses

Silicones

What are Silicones?

Silicones are synthetic polymers containing silicon, oxygen, carbon, and hydrogen. They have a backbone of alternating silicon and oxygen atoms (–Si–O–Si–) with organic groups attached to the silicon. Due to their unique structure, silicones exhibit properties such as thermal stability, water repellence, flexibility, and resistance to chemicals.

Method of Preparation

One common method of preparing silicones is as follows:

• Silicones are prepared by the hydrolysis of alkyl or aryl substituted chlorosilanes (e.g., dimethyldichlorosilane).
• The hydrolysis produces silanols, which then undergo condensation to form linear or cross-linked polymeric silicones.

Example Reaction:

(CH₃)₂SiCl₂ + 2H₂O → (CH₃)₂Si(OH)₂ + 2HCl

Condensation of silanols:
n (CH₃)₂Si(OH)₂ → [–Si(CH₃)₂–O–]_n + n H₂O

Uses of Silicones

• As lubricants and greases due to their thermal stability.
• In waterproofing fabrics and surfaces.
• As insulating materials in electrical applications.
• In medical implants and prosthetics because of biocompatibility.
• As sealants, adhesives, and coatings in construction and industry.

Asked in North East Hill University, UG 4th Semester 2022