Polymer

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Polymer

  1. 1. Introduction to Polymers 1
  2. 2.  What are polymers, monomers and Polymerizations? What are polymer and polymerization types?  The addition-condensation system  The chain growth-step growth system  Nomenclature of polymers  Homopolymer vs. copolymer Classification of polymers depending on their structure Thermosets vs. Thermopalstics Introduction to Polymers 2
  3. 3. Polymers are macromolecules built up by the linking together of large numbers of much smaller molecules. Introduction to Polymers 3
  4. 4. The small molecules which combine with each other to form polymer molecules are termed monomers. Introduction to Polymers 4
  5. 5. Introduction to Polymers 5
  6. 6. Let CH2-CH2 ≈ 1 inch Introduction to Polymers 6 Ethylene Polyethylene Consider only a 200Consider only a 200 - mer, M- mer, Mww ≈ 5600≈ 5600 This ends up with a chain of approximately 1/4 inch (6.4 mm)This ends up with a chain of approximately 1/4 inch (6.4 mm) in diameter and 1/2 mile (805 m) long.in diameter and 1/2 mile (805 m) long. Molecular weights of 1,000,000 are not uncommon for PE …!Molecular weights of 1,000,000 are not uncommon for PE …!
  7. 7. Classification of Polymers Polymer Structure Polymerization Mechanism Step- Polymerization Chain- Polymerization Condensation Polymers Addition Polymers Introduction to Polymers 7
  8. 8. The condensation takes place between two polyfunctional molecules to produce one larger polyfunctional molecule with the possible elimination of a small molecule such as water. The reaction continues until one of the reagents is used up. Introduction to Polymers 8 Polymer StructurePolymer Structure The addition-condensation systemThe addition-condensation system
  9. 9. Introduction to Polymers 9 Adipoyl chloride Hexamethylene diamine Nylone 6/6 Polymer StructurePolymer Structure The addition-condensation systemThe addition-condensation system
  10. 10. Addition polymers are those formed from monomers without the loss of a small molecule. Introduction to Polymers 10 What are addition polymers?What are addition polymers? Y Y
  11. 11. The major addition polymers are those formed by polymerization of monomers containing carbon- carbon double bond; such monomers are called vinyl monomers or substituted ethylenes. Introduction to Polymers 11 Polymer StructurePolymer Structure The addition-condensation systemThe addition-condensation system
  12. 12. Introduction to Polymers 12 Usually in this type of polymerization, vinyl monomers react with themselves to form polymers
  13. 13. What about polyurethane, is it condensation or addition polymer? Introduction to Polymers 13 −−− OCO −−− CONH ester amide
  14. 14. Condensation polymers (New definition) Introduction to Polymers 14 Polymers whose repeating units are joinedPolymers whose repeating units are joined together by functional units such as estertogether by functional units such as ester (-OCO-), amide (-NHCO-), urethane (-OCONH-),(-OCO-), amide (-NHCO-), urethane (-OCONH-), sulfide (-SOsulfide (-SO22-) and other linkages.-) and other linkages. -R-Z-R-Z-R-Z-R-Z-R-Z--R-Z-R-Z-R-Z-R-Z-R-Z- R is aliphatic or aromatic grouping and Z is functional unit.R is aliphatic or aromatic grouping and Z is functional unit. Polymer StructurePolymer Structure The addition-condensation systemThe addition-condensation system
  15. 15. There are two major differences between the two mechanisms: 1. The nature of the species that can react with each other. 2. The relationship between polymer molecular size and polymerization conversion. Introduction to Polymers 15 Polymerization MechanismPolymerization Mechanism The step-chain polymerizationThe step-chain polymerization
  16. 16. The characteristic of chain polymer is that polymer growth takes place by monomer reacting only with the reactive centers. Monomer does not react with monomer and the different-sized species such as dimer, trimer, and n-mer do not react with each other. Polymerization ceases when the active centre destroyed by termination reaction(s). Introduction to Polymers 16 Chain polymerizationChain polymerization
  17. 17. Introduction to Polymers 17 Chain polymerization – anionic polymerization ofChain polymerization – anionic polymerization of styrenestyrene But, the following is NOT possible
  18. 18. In step polymerization each polymer formed can react further with monomer or other polymers. Each dimer, trimer, etc. is just as reactive as monomer. By this mechanism, the size of the polymer molecules increases slowly. Introduction to Polymers 18 Step polymerizationStep polymerization
  19. 19. Introduction to Polymers 19 Step polymerization – the production of polyStep polymerization – the production of poly (ethylene terephthalate) (PET)(ethylene terephthalate) (PET)
  20. 20. Introduction to Polymers 20 Step polymerization – the production of polyStep polymerization – the production of poly (ethylene terephthalate) (PET)(ethylene terephthalate) (PET) Next steps: Or……..
  21. 21. Introduction to Polymers 21
  22. 22.  Most simple and frequently used  It is applicable to polymers synthesized from a single monomer as in addition and ring-opening polymerizations.  How to name: simple monomers: add monomer name to the prefix poly without space or hyphen. Introduction to Polymers 22 Nomenclature based on sourceNomenclature based on source
  23. 23. simple monomers Introduction to Polymers 23 Nomenclature based on sourceNomenclature based on source EthyleneEthylene  PolyethylenePolyethylene AcetaldehydeAcetaldehyde  PolyacetaldehydePolyacetaldehyde
  24. 24. Monomers have multiword name or abnormally long name: parenthesis are placed around its name following the prefix poly Introduction to Polymers 24 Nomenclature based on sourceNomenclature based on source 3-methyl-1-pentene3-methyl-1-pentene  Poly (3-methyl-1-pentene)Poly (3-methyl-1-pentene) Propylene oxidePropylene oxide  Poly(propylene oxide)Poly(propylene oxide) ClorotriflouroethyleneClorotriflouroethylene  Poly(clorotriflouroethylene)Poly(clorotriflouroethylene)
  25. 25. Note: condensation polymers synthesized from single reactants are named in a similar manner. Introduction to Polymers 25 Nomenclature based on sourceNomenclature based on source 6-aminocaproic acid6-aminocaproic acid  Poly(6-aminocaproic acid)Poly(6-aminocaproic acid)
  26. 26. Homopolymers are polymers composed of only one repeating unit in their molecules. Introduction to Polymers 26 What are homopolymers?What are homopolymers? What are copolymers?What are copolymers? Copolymers are polymers composed of two differentCopolymers are polymers composed of two different repeating units in their molecules.repeating units in their molecules. Such asSuch as Styrene Acrylonitirle Be careful !!!
  27. 27. Introduction to Polymers 27 Types of copolymer systemsTypes of copolymer systems Random copolymerRandom copolymer -AABABBBABBAAAA--AABABBBABBAAAA- Alternating copolymerAlternating copolymer -ABABABABABABAB--ABABABABABABAB- Block copolymerBlock copolymer -AAA-BBBBBB-AAAA-BB--AAA-BBBBBB-AAAA-BB- Graft copolymerGraft copolymer
  28. 28. Linear polymers Introduction to Polymers 28 What if polymerization conditions are changed orWhat if polymerization conditions are changed or different monomer is used, e.g. ethylene vs.different monomer is used, e.g. ethylene vs. butadiene?butadiene?
  29. 29. Branched polymers Introduction to Polymers 29 What is the effect of branching on polymer properties? Crystallinity Is it branched polymer?!!!
  30. 30. Cross-linked polymers Introduction to Polymers 30 Using appropriate monomers Chemical reactions Polymer molecules are connected together at points other than their ends Crosslinked polymers do not dissolve but can be swelled by liquids. Light crosslinking improves elasticity properties ⇒ polymer is used as rubber High degree of crosslinking gives high rigidity and thermal stability (high melting point). BOTH CROSSLINKED POLYMERS CANNOT BE RECYLED OR REPOROCESSED
  31. 31. Cross-linked polymers Examples Introduction to Polymers 31 Show the polymer formed by the reaction of the following monomers. Is the resulting polymer linear or branched/cross-linked? Solution
  32. 32. Cross-linked polymers Examples Introduction to Polymers 32 Show the polymer formed by the reaction of the following monomers. Is the resulting polymer linear or branched/cross-linked? Solution
  33. 33. What are thermoset polymers? Introduction to Polymers 33 Polymers that will not flow when heated. ThermosetsPolymers that will not flow when heated. Thermosets have cross-linked structure. Examples are phenolichave cross-linked structure. Examples are phenolic and epoxy resins.and epoxy resins. What areWhat are thermoplasticthermoplastic polymers?polymers? Polymers that soften, without chemical change, and takePolymers that soften, without chemical change, and take new shapes by the application of heat and pressurenew shapes by the application of heat and pressure and harden when cooled. Thermoplastics have linearand harden when cooled. Thermoplastics have linear and branched structures. Examples are PP, PVC andand branched structures. Examples are PP, PVC and NylonNylon
  34. 34. Introduction to Polymers 34 Plastics Thermosets Thermoplastics Amorphous Crystalline Highly cross-linked Lightly cross-linked Classification of polymers – polymer structureClassification of polymers – polymer structure
  35. 35. Introduction to Polymers 35 phenol formaldehyde Phenol-formaldehyde
  36. 36. Introduction to Polymers 36 Is this a homopolymer or copolymer? Why?Is this a homopolymer or copolymer? Why? The monomer composed of more than one structural unit
  37. 37. Introduction to Polymers 37 Branched polymerBranched polymer

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