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https://docs.google.com/document/d/1EjaCWy-XEPMO4eLd3d4SMv5W1qm4qQqi/edit?usp=share_link&ouid=109474854956598892099&rtpof=true polymerization - addition and condensation, copolymerization; Natural and synthetic rubber and vulcanization; some important polymers with emphasis on their monomers and uses - polythene, nylon, polyester and bakelite. A polymer is a large but single chain-like molecule in which the repeating units derived from small molecules called monomers are held together. The process by which monomers t ransf orm into a polymer is called polymerization. CLASSIFICATION OF POLYMERS Classification based on source of availability. Natural Polymers : Natural polymers include starch, cellulose and natural rubber. Starches are polymers of glucose. Cellulose is also a polymer of glucose. It is made by plants from glucose produced during photo- synthesis. Similarly, protein is obtained as a result of polymerization of amino-acids. Natural rubber is a polymer consisting of repeated units of the hydrocarbons 2-methyl-1, 3-butadiene (isoprene). CHAPTER INCLUDES Classification of Polymers Based on source of availability Based on molecular forces Based on mode of polymerisation General Methods of Polymerisation nCH2 C CH CH3 CH2 ⎯⎯Pol⎯ym⎯eriz⎯a t⎯io⎯n → CH2 C CH CH2 CH3 Natural rubber Addition polymerisation Isoprene Synthetic polymers: Synthetic polymers are man-made polymers. e.g., Polyethene, Polystyrene, PVC, Bakelite, Nylon and Dacron. Neoprene rubber : Neoprene rubber is prepared from chloroprene monomer. Chloroprene is prepared from acetylene 2HC ≡ CH ⎯⎯CH⎯2C⎯l2 →CH2 = CH − C ≡ CH Condensation polymerisation Commercially Important Polymers Synthetic polymers and their applications NH4Cl Vinylacetylene nCH2 Cl CH C CH2 Polymerisation (1, 4-Addition) CH2 Cl CH C CH2 Neoprene rubber n Styrene Butadine Rubber (SBR) : Styrene-Butadiene Rubber is a copolymer made up of styrene and 1, 3-butadiene. n CH CH2 + nCH2 CH CH CH2 Styrene 1, 3-Butadiene Polymerisation (1, 4-addition) CH2 CH2 CH (SBR) CH CH2 n Classification based on molecular forces : Elastomers : In elastomers, the polymer chains are held together by the weakest intermolecular forces. e.g., Vulcanized rubber. Fibres : The polymers which are used for making fibre possess high tensile strength and high modulus. This can be attributed to the strong intermolecular forces like hydrogen bonding for example, polyamides (e.g., nylon-66). Thermoplastics : The intermolecular forces of attraction in thermoplastic polymers are intermediary to those of elastomers and fibres. As a result, these can be easily moulded by heating. In thermoplastic polymers there is no cross-linking between chains. e.g., Polyethylene, Polystyrene, etc. Thermosetting : These polymers are normally made from relatively low molecular mass semi-fluid polymers which when heated in a mould become infusible and form an insoluble hard mass. This happens due to extensive cross-linking between different polymer chains. e.g., Bakelite. Classification based on mode of polymerisation : Homopolymer and copolymer : Polymers made by polymerisation of a single monomeric species are known as homopolymer. nCH2 CH2 —( CH2 — CH2)n— (polyethene) Polymers made by more than one type of monomers are known as co-polymers. nCH2 CH CH CH2 + nC6H5 CH CH2 ( CH2 CH CH CH2 CH CH2 )n buta-1, 3-diene styrene Styrenebutadiene rubber C6H5 Addition and condensation polymers : Polymers formed due to addition between monomer molecules possessing multiple bonds through π-bond without removal of any species are called addition polymers. e.g., Polyethylene, styrenebutadiene rubber are addition polymers. Polymers formed by condensation between monomeric units with elimination of small molecules such as water, NH3 or alcohol etc. are called condensation polymers. GENERAL METHODS OF POLYMERISATION Addition polymerisation : The mode of polymerisation can take place through formation of either radical or anionic or cationic species. This process is called chain growth polymerisation, because it takes place through stages leading to increase of chain length and each stage produces reactive intermediate for use in the next stage of the growth of the chain. Radical addition polmerisation : It is initiated by a source of radical and terminated by another radical. Cationic addition polymerisation : Such type of polymers are initiated by any acid and terminated by any base. Presence of electron-donating group in the monomeric unit increases the ease of cationic addition polymerisation. JEE main Polymers Anionic addition polymerisation : Such type of polymerisation is initiated by a base and terminated by any acid. Presence of electron-withdrawing group in the monomeric unit increases the ease of anionic addition polymerisation. COMMERCIALLY IMPORTANT POLYMERS Polyamides Nylon-66 - from adipic acid and hexamethylene diamine HOOC (CH2)4 COOH + NH2 (CH2)6 NH2 O O ( NH (CH2)6 NH C (CH2)4 C)n amide group Nylon 66 Nylon-6 - from Caprolactam O H ( C (CH2 5 N )n Nylon 6 Formaldehyde resins Phenol formaldehyde resins (Bakelite) - from phenol and formaldehyde OH H + C = O H H+ OH– OH CH2OH + OH CH2OH OH OH OH H2C CH2 CH2 (linear polymer) OH OH CH2 H H CH2 C O Strong heating OH CH2 CH2 CH2 CH2 CH2 OH OH OH CH2 Bakelite (cross linked polymer) Polymers JEE main Melamine formaldehyde resin - from melamine and formaldehyde. H2N N NH2 H HN N NH – CH2 N N NH2 + C O H N N NH SYNTHETIC POLYMERS AND THEIR APPLICATIONS Addition Polymers Polymer Monomer Application Polyethylene Ethene → CH2 = CH2 Propene → CH3 – CH = CH2 Styrene → C6H5 – CH = CH2 Chloroprene CH2 = C – CH = CH2 Cl Styrene → CH = CH2, Butadiene → CH2=CH–CH=CH2 Methyl methacrylate CH3 CH2 = C – COOCH3 CH2 = CH – COOC2H5 Acrylonitrile → CH2 = CH – CN Vinyl chloride → CH2 = CH – Cl Tetrafluoro ethylene → CF2 = CF2 Packing material carry bags, insulation for electrical wires and cables... etc. Polypropylene Packing of textiles and foods, linears for bags, heat shrinkage wraps, carpet fibres... etc. Polystyrene or Styron Plastic toys, house hold wares radio and television bodies Neoprene shoe heels, stoppers, printing rollers Buna-s Manufacture of tyres, rubber sole, water proof shoes Polyacrylates Lenses, light covers, light shades, air craft windows... etc. Polyethyl acrylate Latex paints adhesives Polyacrylonitrile (PAN)(orlon) For making clothes, carpets, blankets... etc. Polyvinyl chloride (PVC) Good electrical insulator, hose pipes, rain coats, hand bags... etc. Polytetrafluoro ethylene (PTFE) (Teflon) For nonstick utensils coating etc. Condensation Polymers Polymer Monomer Application Terylene Ethylene glycol– HO – CH2 – CH2 – OH Terephthalic acid – HOOC COOH Ethylene glycol – HO – CH2 – CH2 – OH Phthalic acid – COOH COOH For wash and wear fabric tyre cords, seat or dacron belts and sails Glyptal or Alkyd resin Paints and Lacquers JEE main Polymers Nylon 6, 6 Adipic acid – HOOC –(CH2)4–COOH Hexamethylenediamine – H2N –(CH2)6 – NH2 H2N(CH2)6NH2 Hexamethylene diamine Sebacic acid – HOOC – (CH2)8COOH H N O Caprolactum – OH Phenol Formaldehyde, HCHO Melamine and Formaldehyde NH2 N N and HCHO NH2 N NH2 O Urea NH2 — C — NH2 Formaldehyde HCHO Textile fabrics Nylon 6, 10 Textile fabrics, carpets, bristles for brushes Nylon 6 Mountainering ropes, tyre cords fabrics Bakelite As binding glue for wood varnishes, lacquers Melamine Formaldehyde resin Non-breakable Urea formaldehyde resin Buttons, bottle caps, surgical items Biodegradable Polymer Name Monomer Uses (i) Poly-β -hydroxy butyrate-Co- β hydroxy valerate [PHBV]. OH CH3 – CH – CH2COOH 3- hydroxybutanoic acid OH CH3 – CH2 – CH – CH2COOH 3-hydroxypentanoic acid As packaging orthopaedic devices and in controlled drug release. ❑ ❑ ❑