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Introduction to Polymer Chemistry


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Discussing about the fundamental principles of polymer chemistry emphasising on the type of reactions for making polymers.

Published in: Science, Technology, Business
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Introduction to Polymer Chemistry

  1. 1. Organic Chemistry V Introduction to Polymer Chemistry Indra Yudhipratama
  2. 2. Outline  Defining the terms in polymer  Type of polymers  Polymer synthesis (Polymerisation) and the properties of its product  Addition polymerisation  Polyalkenes  Condensation polymerisation  Polyesters  Polyamides  Enhancing the polymers
  3. 3. Introduction  Polymers in daily life  All of those are synthetic polymers.  Mother nature also produces polymers.
  4. 4. Defining Polymer  Polymers  Poly (many) + mer (unit)  Hence polymer is a macromolecule that is built from smaller unit (monomer)  Proteins are built from many amino acids. Proteins are polymers, amino acids are the monomers  A polymer can be built from the same monomer Homopolymer e.g. Poly(tetrafluoroethene)  Also can be built from different monomers Copolymer e.g. ABS (Acrylonitrile-Butadiene-Styrene)
  5. 5. Type of Polymers Poly(tetrafluoroethene) ABS
  6. 6. Polymerisation  Addition polymerisation  Involving radicals chemistry  Three main steps:  Initiation  An initiator is required to start reaction  Propagation  The chain is propagated to form a long chain  Termination  Reacts with another radical species to stop the reaction
  7. 7. Addition Polymerisation  E.g. Synthesis of Poly(chloroethene) or PVC  Initiation step  Propagation step  Termination step
  8. 8. Addition Polymerisation  The product of addition polymerisation  From alkene alkane, hence stronger in structure.  More rigid/solid structure  The products could have different arrangement:  Regular structure provides rigid, tough, heat resistant polymers. Known as Isotactic  Commonly used for food containers, hospital equipments.
  9. 9. Addition Polymerisation  The product could have different arrangement:  Irregular structure provides more flexible and softer polymers. Known as atactic.  Used as sealants and coatings.  Third type, the functional group alternates between one side and others, known as syndiotactic. This also has regular structure.
  10. 10. Condensation Polymerisation  Producing small molecules as side products.  Commonly water is the small molecules, hence the process known as condensation.  Polyester formation  Difunctional groups are required to form condensation polymers.  Dicarboxylic acids with diols to form polyesters
  11. 11. Polyesters Polyesters in daily life  Poly(ethylene terephtalate) or known as PET.  The monomers are phtalic acid and ethane-1,2-diol.  A rigid structure due to benzene rings.  Used as plastic bottle
  12. 12. Polyamides  Has amide linkage, occur in nature e.g. proteins.  Formed from amino acids  Synthesised in laboratory from diacyl chlorides and diamines  Problem in synthesis with dicarboxylic acids and diamines
  13. 13. Polyamides  Polyamides in daily life  Nylon  Two types of nylon:  Nylon-6  Synthesised from caprolactam
  14. 14. Polyamides  Two types of nylon:  Nylon-6,6  Synthesised from hexane-1,6-dioic acid and 1,6-diaminohexane  Long alkyl chain gives the flexibility of nylon.  Strong structure of polyamides due to hydrogen bonding and amide bonds  No strong hydrogen bonding in polyesters
  15. 15. Enhancing the Polymers’ Properties  Some polymers are synthesised to meet the market requirements.  Properties of polymers determine its function on the market  Example: Hardness, hydrophilicity  Changing the monomers would change the properties of polymers  Some methods to change the hardness of the polymers:  Using cross-linker  Shortening the monomer chain  Using the aromatic functional group
  16. 16. Enhancing the Polymers’ Properties  Forming crosslink  Natural rubber (rubber band) vs Tyres  Both of them are poly(isoprene)  Tyres manufacturing using sulphur as cross-linker  Vulcanisation process  Bind different polymer chains covalently
  17. 17. Enhancing the Polymers  Vulcanisation process  Sulphur as cross-linker  The covalent bonds of sulphur keeps the shape
  18. 18. Enhancing the Polymers  Forming crosslink  Manipulating the monomers  Difunctional monomers are used  Case of contact lenses  Can be polymerised at both ends  Forming polymer networks  hydrogels
  19. 19. Enhancing the Polymers  Shortening the monomers  Case of pacemaker (polyurethanes)  Polyurethanes are copolymer  Consists of different monomers  Shorter chain (blue) gives the rigidity while the longer chain (red) gives the flexibility over the pacemaker  The flexibility over sp3 carbon chain (free rotation)
  20. 20. Enhancing the Polymers  Using aromatic functional group  Case of Nylon vs Kevlar  The planar structure of benzene ring causes the polymer can be packed more closely.  Increase rigidity of the polymer
  21. 21. Inorganic Polymers  Non-carbon based polymers can also be synthesised  Silicone  Si-based polymers  PDMS Poly(dimethylsiloxane)  Hydrophobic liquid polymer with highly flexible chains  Widely used in shampoo formulation  Known as dimethicone
  22. 22. Inorganic Polymers  Silicone hybrid  Used in contact lenses  Combined with carbon-based polymers