Ques. 1AIPMT 2009
The straight chain polymer is formed by
- hydrolysis of CH3SiCl3 followed by condensation polymerisation
- hydrolysis of (CH3)4Si by addition polymerisation
- hydrolysis of (CH3)2SiCl2 followed by condensation polymerisation
- hydrolysis of (CH3)3SiCl followed by condensation polymerisation
Answer
(3) hydrolysis of (CH3)2SiCl2 followed by condensation polymerisation
Solution
As per NCERT, hydrolysis of dimethyldichlorosilane gives a silanediol with two –OH groups:
(CH3)2SiCl2 + 2H2O (CH3)2Si(OH)2 + 2HCl
each unit has two reactive –OH groups, so condensation polymerisation links them end to end into a straight chain silicone, –[–O–Si(CH3)2–]n–.
CH3SiCl3 gives three –OH groups (cross-linked polymer) and (CH3)3SiCl gives only one –OH group (chain stopper, dimer only).
Answer: (3)