Polymers Formula - Classifications And Types

Polymers are macromolecules composed of repeating structural units called monomers.

Formula example:

Polyethylene is derived from ethylene monomer:

CH ₂ = CH ₂

Classification of Polymers

Based on Origin:

Natural:

e.g . Cellulose: [−C ₆ H ₁₀ O ₅ ​−] _n ​

Synthetic:

e.g. Nylon-6: [−NH−(CH ₂ ) ₅ −CO−] n ​

Semi-Synthetic:

e.g. Cellulose acetate: [−C ₆ H ₇ O ₂ (OAc) _{3 ​} −] n ​

Based on Structure:

Linear:

e.g. PVC: [−CH ₂ −CHCl−]n ​

Branched:

e.g. Low-density polyethylene (LDPE)

Cross-Linked:

e.g . Bakelite

Types of Polymerization Reactions

Addition Polymerization: It involves the sequential addition of monomers. Example:

Formation of polyethylene from ethene:

n × CH ₂ =CH ₂ ​ → [−CH ₂ −CH ₂ −]n ​

Important Addition Polymers

Polyethylene (PE): [−CH ₂ −CH ₂ −]n ​

Polystyrene (PS): [−CH ₂ ​ −CH(phenyl)−] n , where phenyl is a benzene ring.

Polyvinyl Chloride (PVC): [−CH ₂ −CHCl−] n ​

Poly(methyl methacrylate) (PMMA): [−CH ₂ −C(CH ₃ )(COOCH ₃ )−] n ​

Also read : Surface Chemistry Formula

Condensation Polymerization

It involves the elimination of a small molecule during polymerization, often water.

Mechanism Example:

Formation of nylon-6,6 involves the reaction of a diamine with a dicarboxylic acid. H ₂ N−(CH ₂ ) ₆ −NH ₂ +HOOC−(CH ₂ ) ₄ −COOH → [−NH−(CH ₂ ) ₆ −NH−CO−(CH ₂ ) ₄ −CO−]n ​ +nH2O

Condensation Polymers:

Nylon-6,6: [−NH−(CH ₂ ) ₆ −NH−CO−(CH ₂ ) ₄ −CO−]n ​

Polyester (PET): [−OCH ₂ CH ₂ O−CO−C ₆ H ₄ −CO−]n ​

Also Check – Ammonium Nitrate Formula

Copolymerization

It's the polymerization of two or more different types of monomers.

Equation example:

Styrene and butadiene can copolymerize to form SBR:

n×CH ₂ =CH−phenyl + m×CH ₂ =CH−CH=CH ₂ ​→ SBR copolymer

Rubber

Natural rubber:

Polyisoprene [−CH ₂ −C(CH ₃ )=CH−CH ₂ −]n ​

Types & Preparation:

Natural Rubber: Derived from latex of rubber trees.

Synthetic Rubber:

Examples include Neoprene and nitrile rubber.

Preparation:

SBR is prepared by the copolymerization of styrene and butadiene.

Equation: n×CH ₂ =CH−C ₆ H ₅ (Styrene) + m×CH ₂ =CH−CH=CH ₂ (Butadiene)→SBR

Another commonly known synthetic rubber is Neoprene, which is derived from the polymerization of chloroprene.

Equation: n×CH ₂ =C(CH ₃ )-CH=CH ₂ (Chloroprene)→Neoprene

Biodegradable Polymers:

e.g. Polylactic acid (PLA): Derived from lactic acid monomers.

Also Check – Aluminium Nitrate Formula

Polymers of Commercial Importance

Polypropylene (PP): [−CH ₂ −CH(CH ₃ )−] n ​

Polyethylene Terephthalate (PET): Used for bottles.

Monomers involved:

Ethylene glycol: HO-CH ₂ -CH ₂ -OH

Terephthalic acid: HOOC-C ₆ H ₄ -COOH

When these monomers undergo a condensation reaction (with the elimination of water), they form PET:

n×HO-CH ₂ -CH ₂ -OH + n× HOOC-C ₆ H ₄ -COOH→[-O-CH ₂ -CH ₂ -O-CO-C ₆ H ₄ -CO-]n ​+nH ₂ O

PVC (Polyvinyl chloride) PVC is a widely used polymer for pipes, cables, and more. It is synthesized from the monomer vinyl chloride.

Monomer: Vinyl chloride: CH ₂ = CH-Cl

During polymerization, the double bond in vinyl chloride opens and forms long chains: n×CH ₂ =CH-Cl→[-CH ₂ -CHCl-]n ​

Nylon: Used for textiles, ropes, and various molded components.