Polymers — JEE Advanced

⚡ Memory tricks before the table

Nylon 6,6 = two 6-carbon monomers (hexamethylenediamine + adipic acid). "6,6 = two hexes shaking hands"
Nylon 6 = one monomer (caprolactam), ring opens. "6 alone, breaks its own ring"
Buna-S = Butadiene + Styrene. Buna-N = Butadiene + Acrylonitrile (Nitrile). S=Styrene, N=Nitrile.
Bakelite = Phenol + Formaldehyde. "Bake it in a mould" → thermosetting, can't remould
Dacron/Terylene = ethylene glycol + terephthalic acid → polyester (ester linkage)
Teflon = tetrafluoroethylene. All F's → nothing sticks → non-stick pan
Vulcanisation = sulphur crosslinks at 373–415K. Makes rubber harder + less sticky
Natural rubber = cis-1,4-polyisoprene. Gutta percha = trans-1,4-polyisoprene (hard, non-elastic)

Polymer	Monomer(s)	Type	Linkage	Thermo	Uses
Polythene (LDP)	Ethylene (ethene)	Addition	C–C	Thermo-plastic	Squeeze bottles, flexible pipes, wire insulation
Polythene (HDP)	Ethylene (Ziegler-Natta cat.)	Addition	C–C	Thermo-plastic	Buckets, dustbins, bottles, pipes
Teflon (PTFE)	Tetrafluoroethylene (CF₂=CF₂)	Addition	C–C	Thermo-plastic	Non-stick utensils, oil seals, gaskets
Polyacrylonitrile (Orlon/Acrilan)	Acrylonitrile (CH₂=CH–CN)	Addition	C–C	Thermo-plastic	Substitute for wool, commercial fibres
Polystyrene	Styrene (C₆H₅–CH=CH₂)	Addition	C–C	Thermo-plastic	Packaging, disposable cups
PVC	Vinyl chloride (CH₂=CHCl)	Addition	C–C	Thermo-plastic	Pipes, floor tiles, raincoats, handbags
Buna-S (SBR)	1,3-Butadiene + Styrene	Addition Elastomer	C–C	—	Auto tyres, floor tiles, footwear, cable insulation
Buna-N (NBR)	1,3-Butadiene + Acrylonitrile	Addition Elastomer	C–C	—	Oil-resistant rubber articles
Neoprene	Chloroprene (2-chloro-1,3-butadiene)	Addition Elastomer	C–C	—	Wet suits, hoses, gaskets (flame resistant)
Natural Rubber	Isoprene (2-methyl-1,3-butadiene) — cis	Natural Elastomer	C–C	—	Tyres, gloves (after vulcanisation)
Gutta Percha	Isoprene — trans	Natural	C–C	—	Hard, non-elastic — golf balls, dental
Nylon 6,6	Hexamethylenediamine + Adipic acid	Condensation	–CO–NH– (amide)	Thermo-plastic	Sheets, bristles, textile, parachutes
Nylon 6	Caprolactam (ring opening)	Condensation	–CO–NH– (amide)	Thermo-plastic	Tyre cords, fabrics, ropes
Dacron / Terylene	Ethylene glycol + Terephthalic acid	Condensation	–CO–O– (ester)	Thermo-plastic	Crease-resistant fabric, safety helmets
Bakelite	Phenol + Formaldehyde	Condensation	–CH₂– (methylene)	Thermo-setting	Combs, switches, handles, electrical items
Melamine-formaldehyde	Melamine + Formaldehyde	Condensation	–CH₂–N–	Thermo-setting	Unbreakable crockery, floor tiles
Rayon (Artificial silk)	Cellulose (treated with NaOH + CS₂)	Semi-synthetic	glycosidic	—	Textile, surgical dressings
Cellulose acetate	Cellulose + acetic anhydride	Semi-synthetic	ester	—	Films, photographic films

Polymer

Monomer(s)

Type

Linkage

Thermo

Uses

Polythene (LDP)

Ethylene (ethene)

Addition

C–C

Thermo-plastic

Squeeze bottles, flexible pipes, wire insulation

Polythene (HDP)

Ethylene (Ziegler-Natta cat.)

Addition

C–C

Thermo-plastic

Buckets, dustbins, bottles, pipes

Teflon (PTFE)

Tetrafluoroethylene (CF₂=CF₂)

Addition

C–C

Thermo-plastic

Non-stick utensils, oil seals, gaskets

Polyacrylonitrile (Orlon/Acrilan)

Acrylonitrile (CH₂=CH–CN)

Addition

C–C

Thermo-plastic

Substitute for wool, commercial fibres

Polystyrene

Styrene (C₆H₅–CH=CH₂)

Addition

C–C

Thermo-plastic

Packaging, disposable cups

PVC

Vinyl chloride (CH₂=CHCl)

Addition

C–C

Thermo-plastic

Pipes, floor tiles, raincoats, handbags

Buna-S (SBR)

1,3-Butadiene + Styrene

Addition Elastomer

C–C

—

Auto tyres, floor tiles, footwear, cable insulation

Buna-N (NBR)

1,3-Butadiene + Acrylonitrile

Addition Elastomer

C–C

—

Oil-resistant rubber articles

Neoprene

Chloroprene (2-chloro-1,3-butadiene)

Addition Elastomer

C–C

—

Wet suits, hoses, gaskets (flame resistant)

Natural Rubber

Isoprene (2-methyl-1,3-butadiene) — cis

Natural Elastomer

C–C

—

Tyres, gloves (after vulcanisation)

Gutta Percha

Isoprene — trans

Natural

C–C

—

Hard, non-elastic — golf balls, dental

Nylon 6,6

Hexamethylenediamine + Adipic acid

Condensation

–CO–NH– (amide)

Thermo-plastic

Sheets, bristles, textile, parachutes

Nylon 6

Caprolactam (ring opening)

Condensation

–CO–NH– (amide)

Thermo-plastic

Tyre cords, fabrics, ropes

Dacron / Terylene

Ethylene glycol + Terephthalic acid

Condensation

–CO–O– (ester)

Thermo-plastic

Crease-resistant fabric, safety helmets

Bakelite

Phenol + Formaldehyde

Condensation

–CH₂– (methylene)

Thermo-setting

Combs, switches, handles, electrical items

Melamine-formaldehyde

Melamine + Formaldehyde

Condensation

–CH₂–N–

Thermo-setting

Unbreakable crockery, floor tiles

Rayon (Artificial silk)

Cellulose (treated with NaOH + CS₂)

Semi-synthetic

glycosidic

—

Textile, surgical dressings

Cellulose acetate

Cellulose + acetic anhydride

Semi-synthetic

ester

—

Films, photographic films

Vulcanisation of Rubber

Heating raw rubber with sulphur at 373–415 K
S forms crosslinks at double bond sites
Tyre rubber: 5% sulphur
Fixes: softness at high T, brittleness at low T, water absorption
Makes rubber harder, elastic, durable

Addition vs Condensation

Addition: unsaturated monomers, no byproduct, chain growth
Condensation: bifunctional monomers, loses small molecule (H₂O, HCl, alcohol)
Nylon, Dacron, Bakelite = condensation
All rubbers, PVC, Teflon = addition

Thermoplastic vs Thermosetting

Thermoplastic: softens on heating, can remould — linear/slightly branched
Thermosetting: hardens permanently, cannot remould — cross-linked
Bakelite, Melamine = thermosetting
Nylon, PVC, Polythene = thermoplastic

LDP vs HDP Polythene

LDP: high pressure (1000–2000 atm), 350–570K, free radical, branched
HDP: low pressure (6–7 atm), 333–343K, Ziegler-Natta, linear
HDP = harder, more tough, closer packing
LDP = flexible, squeeze bottles

Molecular Forces → Properties

Elastomers: weak van der Waals, coiled chains
Fibres: strong H-bonding (nylon) or dipole interactions → high tensile strength
Plastics: intermediate forces
Nylon H-bonds → crystalline, high tensile

Novolac → Bakelite

Phenol + HCHO (acid cat.) → Novolac (linear, used in paints)
Novolac + more HCHO → Bakelite (cross-linked)
Bakelite = infusible solid, thermosetting
Melamine = harder than Bakelite

Amide linkage –CO–NH–

Nylon 6,6 and Nylon 6
Also in proteins (peptide bond)

Ester linkage –CO–O–

Dacron/Terylene
Also in fats, waxes

Glycosidic linkage

Cellulose, Starch
Natural polysaccharides

Methylene –CH₂– bridge

Bakelite
Cross-links phenol rings

Polymer	Monomer	Linkage	Note
Starch	α-glucose	α-glycosidic	Amylose (linear) + Amylopectin (branched)
Cellulose	β-glucose	β-glycosidic	Linear, structural (plant cell walls)
Proteins	α-amino acids	peptide (–CO–NH–)	Up to 20 different amino acids
Nucleic acids	Nucleotides	phosphodiester	DNA, RNA

Polymer

Monomer

Linkage

Note

Starch

α-glucose

α-glycosidic

Amylose (linear) + Amylopectin (branched)

Cellulose

β-glucose

β-glycosidic

Linear, structural (plant cell walls)

Proteins

α-amino acids

peptide (–CO–NH–)

Up to 20 different amino acids

Nucleic acids

Nucleotides

phosphodiester

DNA, RNA