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Keywords

Keywords. Derive from title Multiple word “keywords” e.g. polysilsesquioxane low earth orbit Brain storm synonyms Without focus = too many unrelated hits If you haven’t already, get it to me today. Research paper topics. 3D Stereolithography with polymers

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Keywords

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  1. Keywords • Derive from title • Multiple word “keywords” • e.g. polysilsesquioxane low earth orbit • Brain storm synonyms • Without focus = too many unrelated hits • If you haven’t already, get it to me today.

  2. Research paper topics • 3D Stereolithography with polymers • Plastic concrete – preparation, properties & applications. • Biocompatibility of silicones • Teflon and fluoropolymers –from Heaven or Hell? • Piezoelectric polymers- how they are made, why they are piezoelectric , and applications. • Plastic in the oceans. How long do plastics last and where do they end up? • Plastic hermetic seals • Gas separation membranes through phase inversion • Thermally induced phase separation of polymeric foams. • The strongest plastic • Major catastrophe(s) due to a polymer • Replacing ivory with plastic (comparison of composition, structure and properties) • Plastic explosives and rocket fuels

  3. Polymers from soybeans • Furan based polymers from corn • Bacterial and fungal attack on polymers • Conducting polymers, new metallic materials • Semiconducting polymers for PV • Semiconducting polymers for OLED’s • Polymers for stealth • Polymers for fire protection • Smart polymers that change properties with external stimuli • Reworkable, healable or removable polymers • Photoresists

  4. Homework • Name files with your last name, and HWK# • Within file, your name, HWK title, descriptive information (like the title of you paper topic) -Never make your audience work

  5. Bibliography homework • Due on 27th at 11:59 PM • Based on your keyword search • J. Am. Chem. Soc. format with title e.g. Doe, J., Smith, J. “Proper bibliographies for Professor Loy’s class,” J. Obsc. Academ. B. S. 2012, 1, 234. Recommend endnote or pages or biblio.

  6. Pseudoscience An established body of knowledge which masquerades as science in an attempt to claim a legitimacy which it would not otherwise be able to achieve on its own terms; it is often known as fringe- or alternative science. The most important of its defects is usually the lack of the carefully controlled and thoughtfully interpreted experiments which provide the foundation of the natural sciences and which contribute to their advancement. Johathan Hope: Theodorus' Spiral (2003) Examples of pseudoscience: Intelligent design, polywater, cold fusion, N-rays, Creationism, holistic medicine, etc…

  7. Detecting Baloney • The discoverer pitches the claim directly to the media. • No peer review or testing of claims is possible • The discoverer says that a powerful establishment is trying to suppress his or her work. • The scientific effect involved is always at the very limit of detection. • At signal noise & no one else can replicate • Requires unique instrumentation or experience • Evidence for a discovery is anecdotal. • The discoverer says a belief is credible because it has endured for centuries. • The discoverer has worked in isolation. • The discoverer must propose new laws of nature to explain an observation.

  8. Polymer Phase Diagrams Solid: amorphous glass (below glass trans) or crystalline & Liquid (above melting point)

  9. Polymer Tacticity: Stereochemical configuration • typical for addition or chain growth polymers • not for typical condensation or step growth polymers

  10. Polymer Tacticity: Polymethylmethacrylate (PMMA) Free radical - atactic Anionic - isotactic isotactic syndiotactic

  11. Why is this important? • Tacticity affects the physical properties • Atactic polymers will generally be amorphous, soft, flexible materials • Isotactic and syndiotactic polymers will be more crystalline, thus harder and less flexible • Polypropylene (PP) is a good example • Atactic PP is a low melting, gooey material • Isoatactic PP is high melting (176º), crystalline, tough material that is industrially useful • Syndiotactic PP has similar properties, but is very clear. It is harder to synthesize

  12. Step Growth Configurations

  13. Step Growth Configurations

  14. Chapter 2: Synthesis of Polymers Two major classes of polymerization mechanisms 1) Step Growth 2) Chain Growth

  15. Step Growth Polymerization: Condensation Poly(ethylene terephthalate) or PET or PETE = polyester Two equivalents of water is lost or condensed for each equivalent of monomers

  16. Dacron if a fiber

  17. Step Growth Polymerization: Condensation Biaxially stretched PETE is “Mylar”

  18. Step growth systems • Epoxies • Polyurethanes & ureas • Nylon & polyesters • Kevlar • Polyaryl ethers (PEEK) • Polysulphones • Polyimides • Polythiophenes & Photovoltaic polymers • Polysulfides and polyphenyl ether

  19. Mechanics of Step Growth: • Many monomers • All are reactive Mole fraction Conversion = 1 – [COCl]/[COCl]0 Each has functionality of 2; Can make two bonds Linear, soluble Nylon polymer

  20. Mechanics of Step Growth: 34 COCl groups; p = 1 - [COCl]/[COCl]0 = 0 conversion

  21. Mechanics of Step Growth: Monomer & Dimers 30 reactive groups p = 1 - [COCl]/[COCl]0 = 1-30/34 = 0.11

  22. Mechanics of Step Growth: Monomer & Dimers & Trimers 19 reactive groups p = 1 - [COCl]/[COCl]0 = 1-19/34 = 0.44

  23. Mechanics of Step Growth: Monomer, Dimers, Trimers, & Tetramers 13 reactive groups p = 1 - [COCl]/[COCl]0 = 1-13/34 = 0.62

  24. Mechanics of Step Growth: Monomer, Dimers, Trimers, Tetramers & Higher 7 reactive groups p = 1 - [COCl]/[COCl]0 = 1-7/34 = 0.80

  25. Mechanics of Step Growth: Monomer, Dimers, Trimers, Tetramers & Higher 3 reactive groups p = 1 - [COCl]/[COCl]0 = 1-3/34 = 0.91

  26. Mechanics of Step Growth: Monomer, Dimers, Trimers, Tetramers & Higher 1 reactive groups p = 1 - [COCl]/[COCl]0 = 1-1/34 = 0.97

  27. Mechanics of Step Growth: Monomer, Dimers, Trimers, Tetramers & Higher If R = R’ = Phenylene = Kevlar Mw = 4014 g/mol 1 reactive groups p = 1 - [COCl]/[COCl]0 = 1-1/34 = 0.97

  28. Step-Growth Polymerization • Because high polymer does not form until the end of the reaction, high molecular weight polymer is not obtained unless high conversion of monomer is achieved. Xn = Degree of polymerization p = mole fraction monomer conversion

  29. Degree of Polymerization for step growth polymers X = [COCl]0/[COCl] = 1/1-p

  30. Mechanics of Step Growth: Monomer, Dimers, Trimers, Tetramers & Higher If R = R’ = Phenylene = Kevlar Mw = 4014 g/mol X or DP = 1/(1-p) = 1/1-0.97 = 1/0.03 = 33

  31. Impact of percent reaction, p, on DP Degree of Polymerization, D.P. = No / N = 1 / (1 - p) Assuming perfect stoichiometry DPmax= (1 + r) / (1 - r) where r molar ratio of reactants if r = [Diacid] / [diol] = 0.99, then DPmax= 199

  32. Effect of Extent of reaction on Number distribution

  33. Effect of Extent of reaction on weight distribution

  34. Problems in Achieving High D. P. 1. Non-equivalence of functional groups a. Monomer impurities 1. Inert impurities (adjust stoichiometry) 2. Monofunctional units terminate chain b. Loss of end groups by degradation c. Loss of end groups by side reactions with media d. Physical losses e. Non-equivalent reactivity f. Cyclization . Unfavorable Equilibrium Constant

  35. Impact of Thermodynamics • Esters from Acids and alcohols Keq = 1-10 • Amides from Acids and amines Keq = 10-1000 • Amides or esters from acid chlorides, Keq >104

  36. Interfacial Polymerization: Nylon Rope trick Driving Reactions forward with physics

  37. Biaxially stretched PETE is “Mylar” Tg = 70 °C Tm = 265 °C Tg < 0 °C Tm = 50 °C

  38. Step Growth Polymerization: Condensation Each reaction occurs at approximately the same rate. Any monomer or growing oligomer can participate

  39. Step Growth Polymerization: Condensation Impurities will kill growth and limit molecular weight Delayed commercialization of condensation polymers

  40. The Guy who got the ball rolling Nylon Polyester Polychoroprene (Neoprene) Dr. Wallace Hume Caruthers Head of DuPont Organic research Labs 50 patents

  41. More Step Growth (Condensation) Polymers & their monomers Polyaramides Tg = NA Tm = 500 °C Twaron (AKZO) Stephanie Louise Kwolek (DuPont) Nomex and Technora

  42. Polyamides via Condensation -- Nylon 66 mp. 265C, Tg 50C, MW 12-15,000 Unoriented elongation 780%

  43. More Step Growth (Condensation) Polymers & their monomers Tg = 150 °C Tm = 267 °C Two phase: interfacial polymerization

  44. More Step Growth (Condensation) Polymers & their monomers Mw = 60-250K Tg = 200 °C; Films pressed at 250 °C Use temperature < 175 °C Stable in air to 500 °C Self-extinguishing

  45. More Step Growth (Non-condensation) Polymers & their monomers isocyanates

  46. Polyphenylene Oxide (PPO) Oxidative Coupling Process Mn 30,000 to 120,000 Amorphous , Tg  210C Crystalline, Tm  270C Brittle point  -170C Thermally Stable to  370C Noryl is a blend with polystyrene

  47. Step Growth Polymers • Polyesters, polyamides, engineering plastics such as polysulfones, polyetherether ketones (PEEK), polyurethanes. • Condensation often occurs. • Polymerization affords high MW late in the game

  48. Step-Growth Non-Condensation Polymerization Polyurethanes [RCO2]2SnBu2 1,4-toluenediisocyanate + 1,3-propanediol

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