Chapter A: Polymer Classification

Polymers are categorized by four parameters. By source: natural (cellulose, starch, proteins, natural rubber), synthetic (polythene, PVC, nylon, Dacron, Bakelite, Teflon), and semi-synthetic (rayon, vulcanized rubber). By structure: linear (HDPE, nylon-6,6), branched (LDPE, amylopectin), and cross-linked/network (Bakelite, melamine-formaldehyde). By polymerization: addition (unsaturated monomers, no byproduct, chain-growth) and condensation (bifunctional monomers, lose H2O, step-growth). By thermal behavior: thermoplastic (can be remolded; polythene, PVC, nylon) and thermosetting (permanent set; Bakelite, melamine).

Chapter B: Addition Polymers

All addition polymers use monomers with C=C double bonds. HDPE: monomer ethene, Ziegler-Natta catalyst (TiCl4 + AlEt3), low pressure → linear chains → high density, strong. LDPE: same monomer, free radical initiator, high pressure (1000–2000 atm) → branched chains → low density, flexible. PVC: vinyl chloride (CH2=CHCl), free radical → pipes, cables. Teflon: tetrafluoroethene (CF2=CF2), extremely chemically inert, non-stick surface. Polystyrene: styrene (C6H5CH=CH2) → packaging, insulation. PAN (Orlon): acrylonitrile (CH2=CHCN) → synthetic acrylic fibers.

Chapter C: Condensation Polymers

Condensation polymers require bifunctional monomers and lose H2O per bond formed. Nylon-6,6: hexamethylenediamine + adipic acid (both 6-carbon; hence "6,6") → polyamide (–CO–NH–), thermoplastic. Nylon-6: caprolactam ring-opening (single monomer) → polyamide. Dacron/PET: ethylene glycol + terephthalic acid → polyester (–COO–), thermoplastic; used for clothing fibers and plastic bottles. Bakelite: phenol + formaldehyde → thermosetting cross-linked network; phenolic resin used in electrical switches.

Chapter D: Rubber and Elastomers

Natural rubber = cis-1,4-polyisoprene; isoprene is the monomer (C5H8). Gutta-percha = trans-1,4-polyisoprene; same formula, rigid due to trans geometry. Vulcanization = heating natural rubber with 2–3% sulfur → S–S cross-links → improved hardness, elasticity, temperature resistance. Buna-S (butadiene + styrene) = synthetic tire rubber. Buna-N (butadiene + acrylonitrile) = oil-resistant rubber. PHBV = biodegradable polyester from bacteria; nylon-2-nylon-6 = biodegradable polyamide.

Chapter E: Atmospheric Pollution

London smog: cool, humid, SO2 + smoke → reducing. Photochemical smog: warm, sunny, NOx + VOCs + UV → O3 + PAN → oxidizing. Acid rain: pH < 5.6 (normal rain = 5.6 from CO2 + H2O → H2CO3); caused by SO2/NOx → H2SO4/HNO3; damages marble (CaCO3 + H2SO4 → CaSO4), acidifies lakes. Greenhouse gases: CO2, CH4, N2O, CFCs, H2O vapor trap IR → global warming. Ozone depletion: CFCs → Cl• (UV) → Cl• + O3 → ClO• + O2; ClO• + O• → Cl• + O2 (net: O3 + O• → 2O2; Cl• = catalyst, ~100,000 O3 destroyed per Cl•).

Chapter F: Water and Soil Pollution

BOD: clean water < 5 ppm; polluted > 17 ppm. Eutrophication: N + P → algal bloom → O2 depletion. Heavy metals: Hg → Minamata (neurological), Cd → Itai-Itai $\frac{bone}{kidney}$, Pb → neurological. DDT: persistent, lipophilic → biomagnification. Green chemistry: prevention, atom economy, H2O2 as oxidant, safer solvents, renewable feedstocks.