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15. Introduction to Polymer Chemistry Cacang 12th Science 12th Chemistry Syllabus 1. Introduction 2, Classification of polymers 2.41 Classification of polymers on the basis of source or origin 2.2 Classification of polymers on the basis of structure 2.3 Classification of polymers on the basis of mode of polymerization 2.4 Classification of polymers on the basis of intermolecular forces 2.5 Classification of polymers on the basis of type of different monomers 2.6 Classification of polymers on the basis of biodegradability 3. Some important polymers : 3.1 Rubber 3.2 Polythene 3.3 Teflon 3.4 Polyacrylonitrile 3.5 Polyamide polymers 3.6 Polyesters 3.7 Phenol - formaldehyde and related polymers 3.8 Buna-S rubber 3.9 Neoprene 3.10 Viscose rayon 4. Molecular mass and degree of polymerization of polymers 5. Biodegradable polymers 5.1 PHBV 5.2 Nylon 2-nylon 6 6. Commercially important polymers | Theory Notes Q. What are polymers? Q. Explain the term monomer. Q. Give the classification of polymers on the basis of their source, Q. How are polymers classified on the basis of structure? Q. Explain with exam- ples, branched and linear polymers. (Mar. 15, Mark 2) Q. What are branched and liner polymers? How are cross-linked polymers formed? Polymers . Macromolecules having very hi igh molecular weights and composeq of smaller repeating units (monomers) ar e called polymers, Monomers it The smaller repeating structural uni monomers. s of polymer are called Polymerization The process of formation of po! polymerization. lymer from the monomers is called Classification of polymers on the basis of source (Origin) 1) Natural polymers The polymers obtained from natura are called natural polymers. l sources like plants and animals Natural polymers are of two types i) Plant polymers These are obtained from plants. Ex. Cotton, linen, natural rubber etc. ii) Animal polymers These are obtained from animals. Ex. wool, silk etc. 2) Semisynthetic polymers The polymers derived from natural polymers are called semisyn- thetic polymers. They are also called regenerated polymers. Ex. Acetae rayon, viscose rayon, cellulose nitrate, cuprammonium silk etc. ‘ 3) Synthetic polymers (Man made polymers) The polymers prepared in laboratories from some chemical substances are called synthetic polymers. These are of three types: Fibres, synthetic rubbers and plastics. Ex. Nylon, polythene, terylene, etc. Classification of polymers on the basis of structure 1) Linear polymers They have long continuous straight chains without branching. They are derived from bifunctional monomers, Ex. PVC, high density polythene etc, 2) Branched polymers They have long chain with branches. They are derived from monomers having three functional groups or having side chain. Ex. Polypropylene with methyl groups as branches, low density polythene. 3) Network or cross-linked polymers They have network like structures formed due to linking of linear chain polymers by strong covalent bonds. They are derived from polyfunctional monomers. Ex. Bakelite, melamine etc. Q. Write the classification of polymers based on molec- ular forces. Q. What are thermoplastic polymers? (Mar. 14, Mark 1) Q. Explain the term elastomers. (Mar. 13, Mark 1) Q. Explain the term homopolymer. (Mar. 13, Mark 1) Q. Explain the term copolymer. Q. Give the classification of polymers on the basis of biodegradability. R—CH)—CHY + nCH, = CHY —— R-(CH:~ CH¥),CH:~ CHy This step repeats again and again and chain grows. in termination step | Gaston peneteeited step can be stopped by stopping the supply of monomer or by adding impurity like oxygen or by combining two free radicals. 2R-+4CH) — CHY}; CH: — CHY — R4CH:CHY};¢CHYCH,,.R Classification of polymers on the basis of molecular forces 1) Elastomers . They have weakest vender Waal’s forces as intermolecular forces, They are soft rubber like solids with elastic properties. Ex. Neoprene, Vulcanized rubber, Buna - S, Buna - N etc. 2) Fibres ‘ : They have strong hydrogen bonding or strong dipole-dipole forces as intermolecular forces. They have high tensile strength and hence used in textile industries, ropes, tyre cords etc. Fibres are polymeric solids which form threads. Ex. Nylon, terylene etc. 3) Thermoplastic polymers They have intermolecular forces intermediate between elastomers and fibres. They become soft on heating and hard on cooling. Therefore they can be remoulded and recycled. Ex, Polythene, polystyrene, PVC etc. 4) Thermosetting polymers These are cross-linked polymers. They do not become soft on heating. Therefore they cannot be remoulded and reused. These are rigid polymers. Ex. Bakelite Classification of polymers on the basis of type of monomers 1) Chain growth polymers (addition polymers) 2) Step growth polymers (condensation polymers) Homopolymers These polymers are formed by joining same type of monomers. Ex. Polythene, nylon-6, polystyrene etc. Heteropolymers These polymers are formed by joining different types of monomers. Ex. Nylon-6-6, terylene, Buna-S, Buna-N etc. Heteropolymers are also known as co. are 2 -polymers and the process is called copolymerization. Classification of polymers on the basi: is of biodegradability Polymers are of two types on the basis of biodegradability 1) Non-biodegradable polymers Synthetic polymers which are not affected by microbes are called non-biodegradable polymers, They remain in the environment for very long time and may cause pollution. 2) Biodegradable polymers Natural polymers which de; grade on their own are called biodegrad- able polymers. TT 0. Write a short note on natural rubber? Q. What is vulcanization of rubber? Q. Give the properties of natural rubber. Q. How is polythene prepared? (Mar. 16, Mark 1) Natural Rubber . It is a linear polymer of isoprene ie. Q- methyl- 1,3 -butadiene. CHs | H.C = C—CH = CH: (isoprene) isci i re i i ibber tree Natural rubber is cis-1,4-polyisoprene. Itis obtained fromru t as a latex, It has long flexible chains and shows elastic properties. Its molecular mass varies from 130,000u to 340,000u. HC H NS oth cH NN CeO N GSN Nog moc No SOON Ct CH, HC H (natural rubber) The polymerization process of formation of natural rubber from isoprene units is given below - CHs ‘ii pelymeriaton | te-cad: mcecncu=cn | TC Lge ct it Gutta- Percha is naturally occurring trans- 1,4-polyisoprene. It is not elastic. Vulcanization of Rubber 1) It was discovered by Charles Goodyear. ; 2) The process by which a network of cross links is introduced into an elastomer is called vulcanization. 3) In sulfur vulcanization, natural rubber is mixed with sulfur and heated for certain time. During this process cis- 1,4-polyisoprene chains are cross linked through disulphide (-S-S-) bonds. 5) Natural rubber is soft, sticky with less tensile strength while vulcanized rubber is strong, tough and elastic. 6) Physical properties and hardness of the vulcanized rubber depend on the amount of sulphur used in vulcanization process. 4 Properties of Natural Rubber 1) Natural rubber has polyisoprene chain of isoprene units having cis configuration. 2) It shows elastic property Polythene It is the simplest addition polymer of ethylene monomer. It is hydro- carbon thermoplastic polymer. nCHy = CH, 2" 1CH,— CHsE (ethene) (polythene) It is of two types - a) Low Density Polyethylene (LDP) 1) It is a branched addition polymer. 2) Polymerization of ethylene under pressure (1000-2000 atm) and temperature (350-570 K) in presence of traces of O» or peroxide as initiator produces LDP. nCH» = CH; +g LDP : ; ae 3) The mechanism of this reaction involves free radical addition and H-atom abstraction. Q. How is nylon - 6, 6 prepared? (Oct. 14, Mark 2) Q. Write the reaction for the preparation of Nylon-6. Q. Write the uses of nylon Jibres. + Nylon ~ 6,6 Nylon - 66 is li ide, co-polymer containing -CO-NH-linkages, a linear, polyamide, ‘pols It has high molecular mass (12000 - 50000 u). Monomers The monomers of nylon - 6,6 are adipic acid and hexamethylene diamine. H2N—(CH,),—NH, | HOOC~(CH:),~ COOH {hexamethylene-diamine) (adipic acid) Polymerization Adipic acid is treated with hexamethylene_diamine to form hexam- —(CH,),- COO Polymer Nylon salt is heated to about 553 K temperature and high pressure to form polymer of nylon - 6, 6. H.N —(CH2),— NH; + 00C — (CH), — COO {heaamethylene diammontum edipate) (nylon salt) [-NH - (CH)),— NH — OC — (CH), ~ CO ~], (nylon=6,6) Nylon-6 It is a polyamide and homopolymer fibre containing many amide linkages (-CO-—NH-). Monomer The monomer of nylon-6 is epsilon (€)-caprolactam. Polymerization When €-caprolactam is heated with water at high temperature, it undergoes ring opening polymerization and forms nylon-6. NN H.C c=0 | \ atta NH -(CH.),-— COL 393-543K \ M4 (nylon~6) CH, — CH: (€— caprolactam) H Nylon-6 has high tensile strength and luster. Uses of Nylon - 6 and Nylon - 6,6 1) They are used to prepare brushes, tubes, toys etc. 2) They are used to prepare surgical sutures. 3) They are used to prepare fishing nets, ropes and tyre cords. 4) They are used in textile industries. 5) They are also used in paints and coatings. 6) They are used in making sarees, shirts, bed covers etc. Q. How is terylene prepared? Q. Write the names of monomers used in preparing polymer- dacron Q. Give the physical proper- ties of synthetic fibres. Q. Write any ‘two’ uses of terylene. (Oct. 14, Mark 1) Q. Give the preparation of bakelite polymer. Q. Write the chemical reac- tion to prepare novolac polymer. (Mar. 13, Mark 2) Q. Write the mechanism of polymerization of phenol and formaldehyde using basic and acidic catalyst to prepare bakelite. Q. Write the reaction to prepare Novolac polymer. | Q. Write the uses of bakelite. Terylene (Dacron or Polyester) Terylene is a polyester fibre. Monomers The monomers of terylene are ethylene glycol. HO ~ CH, ~ CH:~ OH CH;— OOC Oy COO — CH; (ethylene ec) {dimethyl terephthalate) (DMT) dimethyl terepthalate (DMT) anq Polymerization Dimethyl terepthate i a in presence of catalyst zinc acetate or anti terylene. s heated at (420 - 460K) with ethylene glycol, mony trioxide to form coo- cH: lO nHO — CH,—CH:— OH + nCH;—OOC “ethylene glycol) (Gimethyt terephthalate) (DMT) —O — CH, — CH: ~ OOC co- n (terylene) Physical Properties of Synthetic Fibres 1) They have high tensile strength. 2) They are wrinkle proof. 3) They are chemically inert. 4) They are resistant to acids and alkalies. 5) They absorb less water and dry quickly. Uses of Terylene 1) It is used in textile industry. 2) It is used to prepare fishing nets, tyre cords, conveyor belts etc. 3) It is used in magnetic recording tape. 4) It is blended with cotton to form terycot and with wool to form terywool. 5) It is used in making bottles, containers etc. 6) It is also used as glass reinforcing materials in safety helmets. Preparation of Bakelite (formaldehyde phenol polymer) 1) The monomers phenol and formaldehyde undergo polymerization in presence of alkali or acid as catalyst. Phenol reacts with form- aldehyde to form ortho or para-hydroxy methyl phenol, which further reacts with phenol and forms a linear polymer called Novolac. Step 1: OH OH OH OH CH,OH CH:OH HOHC CH;:0H oo +CH:0 “= + + Se Sy CH,OH CH,OH Q. Give the preparation of Buna-S Q. Write names and chem- ical formulae of monomers used in preparing Buna-S, (Mar. 14, Mark 2) Q. Give the preparation of neoprene polymer. Q. Give the preparation of viscose rayon. Preparation of Synthetic Rubber Buna -S or Styrene Butadiene Rubber (SBR) | . . It is a copolymer of styrene and 1,3-butadiene. It is vulcanized with sulfur, It is superior to natural rubber. _—_ O AL nCH: = CH=CH = CH, + (oO = [-CH,— CH = CH - CH. ~ CH~ CH] (1.9-butdine) WY (butadiene =styrene copolymer) , (styrene) (25%) Uses - It is used to make tubes of tyres, rubber soles etc. Neoprene 4 It is a condensation polymer of chloroprene (2-chloro-1,3-butadiene). Chloroprene polymerizes rapidly in presence of oxygen to form synthetic rubber neoprene. Vulcanization of neoprene takes place in presence of magnesium oxide. cl cl Polymerization | | nCH, = C- CH= CH» -LcH,-C = CH- CH: (chloroprene) (acoprese) Fig. (a) Polymerization see Chan © = CH— CH2— CH2— G =CH-CH:-..... cl cl +MgO +MgO cl cl vulconization ie) 10) | | sins ~ CH2— C = CH — CH)»— CH) — C = CH CH... Fig. (b) Vulcanization of neoprene Neoprene is resistant to petroleum, vegetable oils, light and heat. Uses 1) It is used in making hose pipes for transport of gasoline and making gaskets. 2) It is used in the manufacture of insulator cable, jackets, belts for power transmission and conveying. Viscose rayon - a Viscose rayon is a semisynthetic fibre which is regenerated cellulose. Preparation Cellulose (represented as cell-OH) in the form of wood pulp is treated with concentrated NaOH solution to get fluffy alkali cellulose. It is then treated with carbon disulphide to form xanthate. It is mixed with dilute NaOH to form viscose solution which is extruded through spinnerates of spinning machine into acid bath when viscose rayon fibres precipitate. 0. Explain molecular mass and degree of polymeriza- tion of polymers. Q. What are biodegradable polymers and non-biode- gradable polymers? Write one example of each. (Mar. 15, Mark 3) Q. What are biodegradable polymers? Give examples. ee Cell = OH + NaOH — Cell, ON * H,0 ibid (alkali cellulose) oe 3° Cell —O- C~SNa Cell — ONa + CS, —— \| S (cellulose xanthate) Cell O-C—SNa Cell-0- C- SH I +H,0 — || | +NaOH 8 S (cellulose. xanthate) Cell -0-C-SH || +HO— Cell- OH ~*+CS 8 cen ces se) Molecular mass and degree of polymerization of polymers 1) A polymer generally consists of molecules of different molecular masses. Hence the molecular mass of a polymer is an average of the molecular masses of constituent molecules. 2) The number of monomer units in a polymer molecule is called the degree of polymerization (DP). 3) Polymers with low molecular mass are brittle and have low mechanical strength while the polymers with high molecular mass are tough. 4) The certain minimum value of molecular mass required to exhibit specific properties, is called critical degree of polymerization. 5) For polymers containing hydrogen bonding the critical degree of polymerization is lower than those containing weak intermolec- ular forces. Non- biodegradable and Biodegradable polymers Polymers which degrade on their own are called pio-degradable polymers. Polymers which are resistant to environmental degrada- tion process are called non-biodegradable polymers. Some biodegradable polymers are given below- i) PHBV polymer (Polyhydroxy butyrate- CO— B—hydroxy valerate) jt is a copolymer of 3- entanoic acid. It has ester linkages. the environment. hydroxy butanoic acid and 3-hydroxy It is degraded by microbes in OH OH | + | — CH-CH:-COOH CHs~ CHe> CH” CH: COOH (> nydroxypentanoie avid) -0- CHCl E- O° FA lI CHs— (g~ hydroxybutanoic cid) CHs 10) CH,CH; O /, (PHBV) ii) Nylon-2 -nylon -6 — , oo, It is a copolymer of glycine and 6-amino caproic acid. It has amide linkages. 
