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

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

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

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

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

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

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

- N - (CH2)6 - N - C - (CH2)4 - C - O n 6 H Nylon 6,6 “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

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

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

Nylon Parachute WWII

Post WWII stocking sale, San Francisco.

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

Linear & branched polymers ex: polyethylene - short branches

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

Low density polyethylene (LDPE) (short branches)

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

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

The phenol + formaldehyde rxn

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

Bakelite - Material of a Thousand Uses Clear Bakelite items Phenolic resin/celluloid clock Bakelite telephone Bakelite camera Bakelite radio Bakelite microphone

Crosslinking Take linear polymer chains & link using covalent bonds

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

Crosslinking