An expert is someone who has made all of the possible mistakes in a very narrow field of study – Niels Bohr An expert is someone who has made all of the possible mistakes in a very narrow field of study – Niels Bohr

Nylons H 2 N - (CH 2 ) 6 - NH 2 + HO - C - (CH 2 ) 4 - C - OH O O H 2 N - (CH 2 ) 6 - N - C - (CH 2 ) 4 - C - OH + H 2 O O O O O O O Adipic Acid Hexamethylene Diamine Amide Group H H

Nylon 6,6 - N - (CH 2 ) 6 - N - C - (CH 2 ) 4 - C - O O O O n n H H 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 “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 “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 “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 - (CH 2 ) 6 - N = C = O + HO - (CH 2 ) 2 - OH O = C = N - (CH 2 ) 6 - N - C - O - (CH 2 ) 2 - OH O O Hexamethylene Diisocyanate Ethylene Glycol Urethane Linkage H H usw.

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

Linear & branched polymers ex: polyethylene Linear & branched polymers ex: polyethylene ~~~CH 2 - CH - CH 2 - CH 2. ~~~CH 2 - CH - CH 2 - CH 2. C4H9C4H9 C4H9C4H9 - - ~~~CH 2 - CH - CH 2 - CH 2 - CH 2 - CH 2. ~~~CH 2 - CH - CH 2 - CH 2 - CH 2 - CH 2. C4H9C4H9 C4H9C4H9 - - Formation of short chain branches in polyethylene ~~~CH 2 - CH CH 2 - CH 2 CH 2.. CH 2 H ~~~CH 2 - CH CH 2 - CH 2 CH 2. CH 2 H H CH 2 = CH 2

Low density polyethylene (LDPE) (short branches) 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 2 O O * * * * * * OH CH 2 2 OH CH 2 2 OH CH OH CH 2 2 OH CH

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

Crosslinking Take linear polymer chains & link using covalent bonds

Crosslinking Ex: rxn of natural rubber or poly(isoprene) with sulfur - interconnects the chains by reacting with the double bonds (vulcanization) with sulfur - interconnects the chains by reacting with the double bonds (vulcanization) H CH 2 - CH 3 - C = C - CH H CH 2 - CH 3 - C = C CH H CH 2 - CH 3 - C = C CH

Crosslinking

Assignment: Review today's classnotes a. nylons b. polyurethanes c. branching d. networks e. Bakelite f. crosslinking g. vulcanization Read: chapter 14 Assignment: Review today's classnotes a. nylons b. polyurethanes c. branching d. networks e. Bakelite f. crosslinking g. vulcanization Read: chapter 14