How to make a monomer into polymer if it is an addition polymer example

Basic Process of Addition Polymerization

Key Steps:

1. Initiation - A catalyst or initiator breaks the double bond in the monomer
2. Propagation - The activated monomer adds to other monomers in a chain reaction
3. Termination - The growing chain stops when two active chain ends meet

Common Examples

1. Ethylene → Polyethylene

Monomer: CH₂=CH₂ (ethylene) Polymer: -(CH₂-CH₂)ₙ- (polyethylene)

Process:

• Heat and pressure with a catalyst (like Ziegler-Natta catalyst)
• The C=C double bond opens up
• Monomers link together through single bonds
• Forms long chains of -CH₂-CH₂- repeating units

2. Propylene → Polypropylene

Monomer: CH₂=CH-CH₃ (propylene) Polymer: -(CH₂-CH(CH₃))ₙ- (polypropylene)

Process:

• Similar to ethylene but with methyl side groups
• Results in a stronger, more heat-resistant polymer

3. Styrene → Polystyrene

Monomer: CH₂=CH-C₆H₅ (styrene) Polymer: -(CH₂-CH(C₆H₅))ₙ- (polystyrene)

Process:

• The benzene ring (C₆H₅) becomes the side group
• Creates the familiar plastic used in disposable cups

4. Vinyl Chloride → PVC

Monomer: CH₂=CHCl (vinyl chloride) Polymer: -(CH₂-CHCl)ₙ- (polyvinyl chloride)

Process:

• Chlorine atoms alternate along the carbon backbone
• Results in PVC plastic used in pipes and flooring

General Reaction Mechanism

Step 1 - Initiation:

Initiator (I•) + CH₂=CHR → I-CH₂-CHR•

Step 2 - Propagation:

I-CH₂-CHR• + CH₂=CHR → I-CH₂-CHR-CH₂-CHR•

This continues adding monomers...

Step 3 - Termination:

Growing chain• + Growing chain• → Final polymer

Key Requirements for Addition Polymerization

Monomer Requirements:

• Must have at least one C=C double bond
• Often has the general structure CH₂=CHR (where R is any group)

Reaction Conditions:

• Catalyst/Initiator: Free radicals, acids, or organometallic compounds
• Temperature: Usually elevated (50-300°C depending on system)
• Pressure: Often high pressure for gases like ethylene
• Solvent: Sometimes needed to control reaction rate

Industrial Example: Making Polyethylene

Raw Materials:

• Ethylene gas (CH₂=CH₂)
• Catalyst (like titanium-based Ziegler-Natta)

Process:

1. Heat ethylene to 150-300°C
2. Apply pressure (1000-3000 atm for high-density PE)
3. Add catalyst to initiate polymerization
4. Control reaction time to achieve desired molecular weight
5. Cool and process the resulting polymer

Result: Long chains with thousands of ethylene units linked together, forming the plastic we use for bags, bottles, and films.

The beauty of addition polymerization is that it simply "adds" monomers together without eliminating any atoms, making it efficient and producing polymers with the same composition as the starting monomers, just in long chain form.