Ziegler-Natta polymerization is a coordination polymerization method discovered by Ziegler and Natta that requires a catalyst formed from transition metal halides and organometallic compounds. The process involves three steps: initiation, propagation, and termination, resulting in the production of various polymers such as polyethylene and polypropylene. However, it cannot be used to generate polyvinyl chloride or acrylates.

1. Zeigler Natta Polymerisation
BY
CH. SAI SRI RAMA CHANDRA MURTHY

2. Ziegler Natta Polymerisation:
It is also called as Co-ordination polymerisation. Zeigler
(1953) and Natta (1955) discovered that in the presence of a
combination of transition metal halides like TCl4, ZnBr3 etc, with
an organometallic compound like triethyl-aluminium or trimethyl-
aluminium, stereospecific polymerisation can be carried out.
Combination of metal halides and organometallic compounds are
called Zeigler Natta catalyst.

3. The π–electrons from propylene end up filling Titanium’s empty
orbital.
Zeigler Natta Catalyst

4. The mechanism involves three steps,
1. Initiation
2. Propagation
3. Termination

5. Initiation:
The catalyst from monomer catalyst complexes by reacting with
monomer molecule.
𝐶𝑎𝑡 + 𝐶𝐻2 = 𝐶𝐻 𝐶𝑎𝑡 −𝐶𝐻2 − 𝐶𝐻𝑅
𝑋
𝑋

6. 𝐶𝑎𝑡 −𝐶𝐻2 − 𝐶𝐻 − 𝑅 + 𝐶𝐻2 = 𝐶𝐻 X
𝐶𝑎𝑡 − 𝐶𝐻2 − 𝐶𝐻 − 𝐶𝐻2 − 𝐶𝐻 − 𝑅+ n(𝐶𝐻2 = 𝐶𝐻)
𝑋
𝑋 𝑋𝑋
𝐶𝑎𝑡 −(𝐶𝐻2 − 𝐶𝐻) − 𝐶𝐻2 − 𝐶𝐻 − 𝐶𝐻2 − 𝐶𝐻 − 𝑅
𝑛
𝑋 𝑋𝑋
Living polymer
Propagation:
The monomer catalyst complex reacts with fresh monomers resulting
the chain growth as show below.

7. 𝐶𝑎𝑡 −(𝐶𝐻2 − 𝐶𝐻) − 𝐶𝐻2 − 𝐶𝐻 − 𝐶𝐻2 − 𝐶𝐻𝑅 + 𝐻𝑋
𝑋 𝑋𝑋𝑋
𝐶𝑎𝑡 −𝑋 + 𝐶𝐻3 − 𝐶𝐻 − (𝐶𝐻2 − 𝐶𝐻) − 𝐶𝐻2 − 𝐶𝐻 − 𝑅
𝑛
𝑋 𝑋 𝑋
Termination:
Termination is carried out with an active halogen compound.
Dead polymer

8. Application:
Used for production of
1. High and low density polyethylene.
2. Thermoplastics.
3. Polyolefins.
4. Polybutylene.
5. Crystalline.
6. Polypropylene.

9. 7. Carbon nanotubes.
8. Nanocomposites.
Limitations:
1. Poly vinyl chloride cannot be generated.
2. Acrylates.