Question

The monomer units of silicones, a water repellent, acid resistant and heat resistant polymer is:
A.\[{\text{Si}}\]
B.\[{\text{Si}}{{\text{O}}_{\text{2}}}\]
C.\[{{\text{R}}_{\text{2}}}{\text{Si}}{\left( {{\text{OH}}} \right)_{\text{2}}}\]
D.\[{\text{RSiOH}}\]

Answer 1

Hint: Silicones also known as polysiloxanes are polymers made up of siloxane. The monomer of silicones will contain alkyl units.

Complete step by step answer:
Silicones are synthetic polymers made up of siloxane\[\left( { - {{\text{R}}_{\text{2}}}{\text{Si }} - {\text{ O }} - {\text{ Si}}{{\text{R}}_{\text{2}}} - } \right)\].
Here the R group can be any organic group. These polymers are colourless, oils or rubber like substances. They are commonly employed as sealants, adhesives and as lubricants. Siloxanes being a poor conductor they are used in thermal and electrical insulation.
The alkyl group is water repellent with par resistance to heat and acid. Thus, they have high bond energy. The presence of alkyl group in monomers of silicones in the place of R makes the polymer water repellent, acid resistant and heat resistant.
Hence, the polymer is \[{{\text{R}}_{\text{2}}}{\text{Si}}{\left( {{\text{OH}}} \right)_{\text{2}}}\].

So, the correct option is C.

Additional information:
The major application of Silicone is sealant which is a versatile and flexible waterproof sealant. The characteristic properties of this sealant is listed below:
1.Permanent elasticity after curing.
2.Has an expectancy of a long life.
3.They do not shrink.
4.They always maintain its colour.
5.Completely resistant to most of the chemicals and solvents.
6.They are non toxic after curing.
7.Possess good adhesion to glass and various other commonly used building materials.
8.They are resistant to high and low temperatures ranging from -60°C to +200°C

Note:
The silicone chain or silicon polymers are also known to be polydimethylsiloxanes which have silicon-oxygen backbone. This is similar to the structure of silica (silicon dioxide) with a difference of organic group R attached by \[{\text{C}} - {\text{Si}}\]bonds.