Question

$M{e}_{3}SiCl$ is used during polymerisation of organo silicones because:

• A. The chain length of organo silicone polymers can be controlled by adding $M{e}_{3}SiCl$
• B. $M{e}_{3}SiCl$ blocks the end terminal of silicone polymer
• C. $M{e}_{3}SiCl$ improves the quality and yield of the polymer
• D. $M{e}_{3}SiCl$ acts as a catalyst during polymerisation

Answer 1

Answer: (A), (B)

The correct options are
A The chain length of organo silicone polymers can be controlled by adding $M{e}_{3}SiCl$
B $M{e}_{3}SiCl$ blocks the end terminal of silicone polymer

Hydrolysis of $(C{H}_3{)}_{3}SiCl$ gives $(C{H}_3{)}_{3}SiOH$, which is volatile and on condensation it gives hexamethyldisiloxane. Since this compound has no $OH$ groups it can not polymerize any further.

Thus when $(C{H}_3{)}_{3}SiCl$ is used during polymerisation of organo silicones , it will block the the end of the straight chain produced by the monomers, since there no functional $-OH$ group will be present.