Topics to be Covered. Elements of Step-Growth Polymerization. Branching Network Formation

Transcription

1 Topics to be Covered Elements of Step-Growth Polymerization Branching Network Formation Chapters 1 & 2 in CD (Polymer Science and Engineering)

2 Dawn of Understanding "I am inclined to think that the development of polymerization is perhaps the biggest thing that chemistry has done, where it has had the biggest effect on everyday life Lord Todd,1980 Ethylene Polyethylene C 2 =C 2 Magic? [-C 2 -C 2 -] n

3 Staudinger My dear chap, give up your ideas on big molecules. There are no organic molecules with a molecular weight of more than Just clean up your products and they will crystallize and reveal themselves as low-molecularweight compounds. C C 2 C C 3 C 2 C 2C C C 2 C 3 A cyclic isoprene dimer C 2 C C 2 C C 2 C C 2 C C 2 C C 2 C C 2 C

4 Timeline 1920 STAUDINGER; The macromolecular hypothesis CARLES STINE; Initiates a program of fundamental research at du Pont. LATE 1920's CARTERS; Set out to prove the existence of macromolecules by systematically building them from small molecules using well known chemistry.

5 Condensation Reactions Acetic Acid Ethyl Alcohol or Ethanol Reversible Reaction! Ethyl Acetate Ester linkage C 3 - C - + C 3 -C 2 - C 3 -C - -C 2 -C If you don t know what this is you should be castigated unmercifully

6 Why do Molecules React? Acetic Acid C 3 -C - kersplat! - C 2 -C 3 Ethyl Alcohol or Ethanol

7 Why do Molecules React? C 3 -C: : - C 2 -C : ~ 2 C 3 -C C 2 -C 3 C 3 -C: -C 2 -C 3 This isn t what really happens, but shows you how the valency electrons get rearranged

8 Making a Polymer Acetic Acid Ethyl Alcohol or Ethanol Reversible Reaction! Ethyl Acetate Ester linkage C 3 - C - + C 3 -C 2 - C 3 -C - -C 2 -C If we heat acetic acid and ethanol up to just over C, to get the reaction going and drive off water, why don t we form polymer?

9 Making a Polymer The molecules are monofunctional; + To make linear chains we need bifunctional molecules; Except the reaction doesn t happen all in one go, like this, but in a step- growth fashion.

10 Making a Polyester Monomers -C -(C 2 ) n - C (C 2 ) m - -C -(C 2 ) n -C - -(C 2 ) m Dimer

11 Making a Polyester -C -(C 2 ) n -C - -(C 2 ) m - + -C -(C 2 ) n -C Trimer -C -(C 2 ) n -C - -(C 2 ) m - -C -(C 2 ) n -C - Note, reacting a diacid and a dialcohol will give you a polyester! M 1 + M 1 M 2 M 2 + M 1 M 3 M 2 + M M 2 4 M 3 + M M 1 4 M 4 + M M 1 5 M 3 + M M 2 5 M 5 + M M 1 6 Etc.

12 The Invention of Nylon Stine offers Carothers a job Carothers and his group succeed in making low molecular weight aliphatic polyesters

13 The molecular still and the shift to polyamides

14 Nylons 2 N - (C 2 ) 6 -N C - (C 2 ) 4 - C - examethylene Diamine Adipic Acid 2 N - (C 2 ) 6 -N -C -(C 2 ) 4 - C Amide Group

15 Nylon 6,6 -N -(C 2 ) 6 -N -C -(C 2 ) 4 -C n

16 Julian ill reenacting the discovery of Nylon

17 Ad. from N.Y. erald Tribune, ct 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

18 Stockings! Demonstration of knitting nylon stockings at the N.Y. World s Fair, 1939

19 Marie Wilson s Leg, 2 ton 35 ft cast, N.Y. World s Fair1939 DuPont did a masterly job in two areas; Advertising Technical Service

20 Why Stockings? As skirts got shorter after the end of WWI, shocking expanses of leg were being revealed and the appearance and "feel" of stockings became a pressing fashion concern. And, there was money to be made! At that time nothing could compare with silk for sheerness. Wool was thick and scratchy; cotton was, well, cotton, not very exciting; rayon also was not sheer enough and tended to droop and bag at the ankles. But, silk was expensive and not very durable (silk stockings would "run" at the slightest provocation). Nevertheless, about 1.6 million pairs of silk stockings were being a day in the U.S. alone! Golden Gate Exposition, 1939

21 Wilmington gets the first nylon stockings, 1939 May Nylon Day. Four Million pairs go on sale throughout the U.S. Supply exhausted in 4 days.

22 Nylon Parachute WWII

23 Betty Grable auctions her stockings for the war effort.

24 Post WWII stocking sale, NYC. She couldn t wait!

25 Post WWII stocking sale, San Francisco.

26 Sold ut!

27 A Tragic End Carothers in happier times.

28 Polymer Synthesis - Classification Carothers suggested that most polymers could be classified into two broad categories according to the mechanism of polymerization; Condensation Addition As you will see, a better classification may be; Step-growth Chain

29 Types of Reactions Condensation 2 N - (C 2 ) 6 -N C - (C 2 ) 4 - C - Nylon 6,6 Addition C 2 = C 2 Polyethylene Ring opening C N Nylon 6

30 Nylon 6,6 -N -(C 2 ) 6 -N -C -(C 2 ) 4 -C n

31 Nylon 6,10 What would nylon 6,10 look like? A B -N -(C 2 ) 6 -N -C -(C 2 ) 10 -C - -N -(C 2 ) 10 -N -C -(C 2 ) 6 -C - n n C -N -(C 2 ) 6 -N -C -(C 2 ) 8 -C - n

32 More on Nylons Applications Carpet Fibers Clothes Gear wheels Etc.

33 Back to Condensation Is a molecule of water always split out? 2 N - (C 2 ) 6 -N 2 examethylene Diamine + Cl-C -(C 2 ) 4 -C -Cl Adipoyl Chloride 2 N - (C 2 ) 6 -N -C -(C 2 ) 4 - C - + Cl Amide Group

34 The Nylon Rope Trick Nylon "skin" carefully drawn off to form fiber or rope examethylene diamine in water Adipoyl chloride in chloroform Nylon 6,6 formed at the interface

35 The Nylon Rope Trick

36 Polyurethanes A reaction that does not involve the splitting out of a small molecule; = C = N - (C 2 ) 6 - N = C = + - (C 2 ) 2 - examethylene Diisocyanate Ethylene Glycol = C = N - (C 2 ) 6 -N-C--(C 2 ) 2 - Urethane Linkage

37 Network Formation ow would you make chains that branch and then perhaps interconnect to form networks? A. Use a mixture of bifunctional and monofunctional units B. Get a tube of Molecular Super Glue and stick a bunch of chains together C. Use multifunctional (f>2) monomers

38 Network Formation The hydrogens in the ortho and para positions to the group, which by convention are not usually shown but here are indicated by a *,can react with fomaldehyde to form (initially) oligomers. * * * + C 2 C 2 C 2 C 2 C 2 C 2 C 2 C 2

39 Another Condensation Reaction

40 Network Formation C2 C2 C2 C2 C 2 C2 C2 C 2 C2 2C C2 2C C2 C 2 C2 C2 C 2 C 2 C2 C 2

41 Step-Growth Polymerization ; Summary

42 Conversion and Molecular Weight in Step-Growth Polymerizations x n = 1 (1 p) (1 - p) Note; you only get high molecular weight polymer at high degrees of conversion Conversion, p 1.0

43 Some Important Step Growth Polymers Nylons Polyesters Polyurethanes Polycarbonate Epoxies Phenolics