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Macromolecules

Macromolecules. K Warne. What do you notice about this structure?. Macromolecules. H. H. H. H. H. H. H. H. H. H. H. H. H. H. H. C. C. C. C. C. C. C. C. C. C. C. C. C. C. C. H. It is made of lots of small repeating units joined together?. H. H. H. H. H. H.

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Macromolecules

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  1. Macromolecules K Warne

  2. What do you notice about this structure? Macromolecules H H H H H H H H H H H H H H H C C C C C C C C C C C C C C C H It is made of lots of small repeating units joined together? H H H H H H H H H H H H H H H H H H H C C C C C H H H H H

  3. These large molecules are referred to as polymers. The repeating unit is usually derived from a small original molecule which is called the monomer? Macromolecules H H H H C C C C H H H H H H H H H H C C C C C C H H H H H H

  4. The small original molecule which makes this polymer isethene. H H Macromolecules C C H H H H H C C C The double bond breaks to form the bonds that link the individual units together. The polymer molecule can stretch up to hundreds or even thousands of units. The formation of a polymer from its monomers is known as polymerisation. H H H H H H H H H H C C C C C C C H H H H H H H

  5. The small original molecule which makes this polymer isethene. The polymer is therefore poly(ethene) or polythene. Macromolecules monomer H H Ethene H H H H H C C (Ethene is usually drawn with bonds at 1200) C C C C C H H H H Poly(ethene) H H H H H H H H H H Polymer C C C C C C C H H H H H H H

  6. Definition - Macromolecule H H H C C C H H H H H H H H H H Note 1: In many cases, especially for synthetic polymers, a molecule can be regarded as having a high relative molecular mass if the addition or removal of one or a few of the units has a negligible effect on the molecular properties. This statement fails in the case of certain properties of macromolecules which may be critically dependent on fine details of the molecular structure, e.g., the enzymatic properties of polypeptides. Note 2: If a part or the whole of the molecule has a high relative molecular mass and essentially comprises the multiple repetition of units derived, actually or conceptually, from molecules of low relative molecular mass, it may be described as either macromolecular or polymeric, or by polymer used adjectivally. Note 3: In most cases, the polymer can actually be made by direct polymerization of its parent monomer but in other cases, e.g., poly(vinyl alcohol), the description �conceptual� denotes that an indirect route is used because the nominal monomer does not exist. Source: IUPAC Polymer Education Website/Glossary: <http://www.iceb.ufop.br/dequi/iupac/polymerglossary/terms_search.php> Macromolecule - Alternative term: polymer molecule Molecule of high relative molecular mass, the structure of which essentially comprises the multiple repetition of (small)unitsderived, actually or conceptually, from molecules of low relative molecular mass. C C C C C C C H H H H H H H

  7. Poly(ethene) or polythene Shorthand representations: (–CH2 – CH2–)n n

  8. Functional groups The functional groupsin a molecule are ………………. or ………………….. of atoms which determine the ……………………. of organic molecules.  Identify the functional group in each molecule below and move it to its appropriate box.

  9. Functional groups The functional groupsin a molecule are atoms or combinations of atoms which determine the properties of organic molecules.  Not needed Not needed

  10. Mixtures - Types

  11. Mixtures - Types

  12. Polymerisation (n ~ 2000 – 20 000) • Reaction conditions: 2000 C, 2000 atmospheres, presence of oxygen initiator. • The reaction proceeds through a set of distinct steps: Initiation, Propagation& Termination • Each of these steps involves a molecule which has one unpaired electron known as a Free Radical (Ra●) which is a highly reactive species. • Initiation: • Propagation: • Termination: • The free radicals, Ra●are produced by reaction between some of the ethene and the oxygen initiator. (The radical can take a number of forms and usually includes at least one oxygen atom.) • R(O) Ra ● (Radicals produced) A free radical joins an ethene molecule and a new longer free radical is formed. (Radicals produce more radicals) Ra●+ CH2=CH2 RaCH2CH2● Ra CH2CH2●+ CH2=CH2 RaCH2CH2CH2CH2●(each time the chain gets longer) Polythene is formed via an addition reaction using free radical polymerisation. The reaction can be represented as: Two free radicals hit each other producing a final molecule. (Two radicals combine) Ra(CH2)n●+ ● (CH2)mRa Ra(CH2)n̶ (CH2)mCH2Ra (The process stops here because no new free radicals are formed.) As chain termination is a random process, poly(ethene) will be made up of chains of a wide variety of different lengths. Mechanism adapted from: www.chemguide.co.uk/mechanisms/freerad/polym.html For an in-depth discussion of this process see: http://www.materialsworldmodules.org/resources/polimarization/3-addition.html

  13. Polymerisation simulations View each of the simulations below (you may need to escape and review the page as slideshow a number of times) to decide which steps are Initiation, Propagation and/or Termination. (Copy/paste or Drag & drop these labels) Initiation Propagation Termination HO● + CH2=CH2  HOCH2CH2 ● HOCH2CH2● + ●CH2CH2OH  HOCH2CH2CH2CH2OH ROCH2CH2● + nCH2=CH2  RO(CH2CH2)nCH2CH2 ●

  14. Polymerisation simulations View each of the simulations below (you may need to escape and review the page as slideshow a number of times) to decide which steps are Initiation, Propagation and/or Termination. Propagation Termination HO● + CH2=CH2  HOCH2CH2 ● HOCH2CH2● + ●CH2CH2OH  HOCH2CH2CH2CH2OH Initiation, Propagation ROCH2CH2● + nCH2=CH2  RO(CH2CH2)nCH2CH2 ● Sources: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  15. Condensation Polymers Carboxylic acids can combine with alcohols to form esters. + H2O +  This reaction is also known as condensation because water is produced. Both carboxylic acids and alcohols can however have two functional groups per molecule. In this case the final products could react again and again... + + (- H2O) (- H2O)  The CH2CH2 groups in these molecules could be replaced with larger chains or even other functional groups to create compounds with different properties... The chain length of the molecule increases and the resulting molecule can continue reacting to increasing the length of the chain further.

  16. Eg: poly(ethylene terephthalate) - PET Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). The next slide has an animation to show the formation of PET PET is used to make soft-drink bottles, magnetic tape, and many other plastic products. poly(ethylene terephthalate) - PET Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  17. Eg: poly(ethylene terephthalate) - PET Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). PET is used to make soft-drink bottles, magnetic tape, and many other plastic products. poly(ethylene terephthalate) - PET Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  18. Eg: poly(ethylene terephthalate) - PET Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). PET is used to make soft-drink bottles, magnetic tape, and many other plastic products. Copy and paste the dotted red box around each ester linkage. poly(ethylene terephthalate) - PET Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  19. Eg: poly(ethylene terephthalate) - PET Since the monomers in these examples are joined by ester linkages, the polymer chain is a polyester. This one is called PET, which stands for poly(ethylene terephthalate). PET is used to make soft-drink bottles, magnetic tape, and many other plastic products. Copy and paste the dotted red box around each ester linkage. Ester linkage poly(ethylene terephthalate) - PET Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  20. Nylon A carboxylic acid monomer and an amine monomer can join in an amide linkage. As before, a water molecule is removed, and an amide linkage is formed. Notice that an acid group remains on one end of the chain, which can react with another amine monomer. Similarly, an amine group remains on the other end of the chain, which can react with another acid monomer. Monomers can therefore continue to join by amide linkages to form a long chain. Because of the type of bond that links the monomers, this polymer is called a polyamide. The polymer made from these two six-carbon monomers is known as nylon-6,6. (Nylon products include hosiery, parachutes, and ropes.) Source: http://www.materialsworldmodules.org/resources/polimarization/4-condensation.html

  21. Kevlar Kevlar is a polymer formed by joing the two monomers; benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene through an amide link. + (- H2O) Kevlar’s strength is enhanced greatly by the presence of cross linking hydrogen bonding between the chains. Sources - Adapted from: http://www.chemguide.co.uk/organicprops/amides/polyamides.html

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