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Some Basic Chemistry: Single and Double Bonds

Learn about single and double bonds, functional groups, condensation reactions, polymers, and nylon development. Understand how branching and crosslinking impact polymer properties and applications. Explore Bakelite and crosslinking in polymers.

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Some Basic Chemistry: Single and Double Bonds

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  1. H – – – C C H C H CH4 – H H H – – C C – – – H C C H C2H6 – – H H H H – – – C C C C – C2H4 – – H H Some Basic Chemistry: Single and Double Bonds

  2. Some Basic Chemistry: Functional Groups CH2=CH2 Ethylene O O = = + R–OH R–C–OH R–C–O–R Alcohol Carboxylic Acid Ester O O = = R–NH2 + R–C–OH R–C–NH–R Amine Carboxylic Acid Amide Functional groups - small groups of atoms held together in specific arrangement by covalent bonds Responsible for principal chemical properties of molecule

  3. O Ester linkage O Ethyl Acetate Some Basic Chemistry: Condensation Reactions Ethyl Alcohol or Ethanol reversible reaction CH3 - C - OH + CH3 - CH2 - OH CH3 - C - O - CH2 - CH3 + H2O Acetic Acid

  4. Now…to make a Polymer These molecules are monofunctional: + To make linear chains need bifunctional molecules: Except, reaction goes step-wise

  5. Polyester - step 1 O O O O Monomers HO - C - (CH2)n - C - OH + HO - (CH2)m - OH HO - C - (CH2)n - C - O - (CH2)m - OH + H2O Dimer

  6. O O HO - C - (CH2)n - C - O - (CH2)m - OH + HO - C - (CH2)n - C - OH O O O O Trimer - H2O HO - C - (CH2)n - C - O - (CH2)m - O - C - (CH2)n - C - OH O O M3 + M2 M5 M1 + M1 M2 M2 + M1 M3 M2 + M2 M4 M3 + M1 M4 M5 + M1 M6 M4 + M1 M5 Etc. Polyester Reacting diacid & dialcohol give polyester

  7. H2N - (CH2)6 - NH2 + HO - C - (CH2)4 - C - OH Hexamethylene Diamine Adipic Acid O O O O H2N - (CH2)6 - N - C - (CH2)4 - C - OH + H2O Amide Group H Nylons

  8. Nylon 6,6 O O - N - (CH2)6 - N - C - (CH2)4 - C - n 6 6 H H “I am making the announcement of a brand new chemical textile fiber ---derivable from coal, air and water -- and characterized by extreme toughness and strength --” Charles Stine V.P. for research, Du Pont, 1938

  9. Nylon “I am making the announcement of a brand new chemical textile fiber ---derivable from coal, air and water -- and characterized by extreme toughness and strength --” Charles Stine V.P. for research, Du Pont, 1938

  10. Nylon May 15 1940 - “Nylon Day” Four million pairs go on sale throughout US Supply exhausted in 4 days.

  11. Nylon Parachute WWII

  12. Post WWII stocking sale, San Francisco.

  13. O = C = N - (CH2)6 - N = C = O + HO - (CH2)2 - OH O Hexamethylene Diisocyanate Ethylene Glycol O = C = N - (CH2)6 - N - C - O - (CH2)2 - OH Urethane Linkage H Polyurethanes Reaction does not involve splitting out of a small molecule usw.

  14. Branched - short branches Linear & branched polymers ex: polyethylene Linear

  15. CH2 - CH2 ~~~CH2 - CH CH2 H .CH2 Formation of short chain branches in polyethylene CH2 - CH2 ~~~CH2 - CH CH2 . CH2H CH2 = CH2 C4H9 - ~~~CH2 - CH - CH2 - CH2. C4H9 - ~~~CH2 - CH - CH2 - CH2- CH2 - CH2. CH2 = CH2 Linear & branched polymers ex: polyethylene

  16. Low density polyethylene (LDPE) (short branches)

  17. Other types of branching short long star Branching suppresses or prevents chain movement & "crystallization" in polymers

  18. Branching Another way to make chains branch * * Use multifunctional (f>2) monomers * OH + CH O 2 OH OH OH CH CH CH 2 2 2 OH CH CH CH 2 2 2 OH OH OH CH 2 OH

  19. The phenol + formaldehyde rxn

  20. Network formation Further reaction under heat & pressure builds up densely cross-linked network. This is Bakelite, a thermosettingpolymer. Once reaction is complete, material cannot be reheated and/or reformed Bakelite

  21. Bakelite - Material of a Thousand Uses Bakelite telephone Clear Bakelite items Phenolic resin/celluloidclock Bakelite radio Bakelite microphone Bakelite camera

  22. Crosslinking Take linear polymer chains & link using covalent bonds

  23. - CH2 CH2 - CH2 CH2 - CH2 CH2 - - - - - - - C = C C = C C = C - - - - - - CH3 H CH3 H CH3 H Crosslinking Ex: rxn of natural rubber or poly(isoprene) with sulfur - interconnects the chains by reacting with the double bonds (vulcanization)

  24. Crosslinking

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