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Molecular architecture

Molecular architecture. Polymer properties depend on molecular architecture (the structure of the molecules) and the physical state of the polymer. HOW DO WE DEFINE MACROMOLECULAR ARCHITECTURE?. Macromolecular architecture.

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Molecular architecture

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  1. Molecular architecture Polymer properties depend on molecular architecture (the structure of the molecules) and the physical state of the polymer. Chapter 2. molecular architecture

  2. HOW DO WE DEFINE MACROMOLECULAR ARCHITECTURE? Chapter 2. molecular architecture

  3. Macromolecular architecture • Constitution: type of atoms in the chain (backbone), type of side groups/branch groups, type of end groups, monomer sequence, molecular weight distribution • Configuration: arrangement of neighboring atoms along the backbone or chain segments • Conformation: the arrangement of the chain in space Constitution and configuration are usually set in the polymerization and/or blending processes. Conformation is a product of the polymer’s environment. Chapter 2. molecular architecture

  4. BR-PE.avi BR-PE_2.avi 1_butene.avi 1_butene_2.avi CASE STUDY: LDPE Chapter 2. molecular architecture

  5. Low density polyethylene Constitution • The high pressure synthesis of LDPE via free radical reactions was one of the first commercial processes at supercritical conditions for the solvent (ethylene is near or above Tc). • Constitution: polymerized from ethylene monomer in a process initiated by free radicals. Some oxygen in the monomer accelerates the process. Other free radical initiators can be used. Chapter 2. molecular architecture

  6. Low density polyethylene Configuration • Statistically, local rearrangements of the chain near the free radical chain end results in short chains being formed (15-25 per 1000 monomer units; 2 – 8 carbon atoms long) • This product has similar properties to ethylene/a-olefin copolymers with 0.25 mol % a-olefin. • Some long chain branching also occurs (0.5 – 4 per 1000 monomer units long). • Both types of branching interfere with crystallite growth and structure. Chapter 2. molecular architecture

  7. Low density polyethylene Conformation • Arrangement of the backbone and side chains in 3-D. • In dilute solution, the C-C backbone will be in the zig-zag conformation, i.e., for carbon atoms lying in the same plane. • This particular conformation represents a local state of low energy for the chain; which can be calculated using conventional molecular dynamics methods • Branches/side chains will disrupt the zig-zag conformation and three dimensional ‘packing’ of neighboring chains in their vicinity. • Much of the LDPE material will form small crystallites, that can act as physical crosslinks. This means that the bulk material will be a flexible solid between Tg (Tg < -100° C; difficult to measure due to rapid crystallization) and Tm (98 < Tm < 115° C). Chapter 2. molecular architecture

  8. HOW DOES MOLECULAR ARCHITECTURE AFFECT PROPERTIES? Chapter 2. molecular architecture

  9. LDPE properties • Crystallites: • Fewer defects means higher crystallinity • Even single crystals are not 100% crystalline due to edges and corners, and defects in the crystallite surfaces themselves. • See Table 1, Appendix B, p. 614 for different polyethylenes • Linear LDPE has ~ 80% crystallinity, Tm ~ 135 °C compared to LDPE with 45-55% crystallinity, and a lower Tm. • Performance: • Excellent flexibility and easy processing • Good structural strength Chapter 2. molecular architecture

  10. Generalization • Within one polymer family, it is possible to infer differences in performance with changes in constitution, configuration and conformation. • It is more difficult to compare across families due to the influence of the different chemical building blocs Chapter 2. molecular architecture

  11. Constitutions Configurations Homopolymers Copolymers C, O, N are the most common elements in synthetic polymer chains Table 2.1 – elements that form long chains SYNTHETIC POLYMERS Chapter 2. molecular architecture

  12. Synthetic polymers with the highest # of literature references. This list is skewed toward thermoplastics. Thermosets and other matrix materials have greater diversity in building blocks, and therefore have fewer specific literature references. TOP 100 POLYMERS Chapter 2. molecular architecture

  13. TOP 100/GENERAL USE Chapter 2. molecular architecture

  14. Top 100/general use Chapter 2. molecular architecture

  15. Top 100/general use Chapter 2. molecular architecture

  16. TOP 100/ENGINEERING PLASTICS Chapter 2. molecular architecture

  17. Top 100/engineering plastics Chapter 2. molecular architecture

  18. TOP 100/THERMOSETS Chapter 2. molecular architecture

  19. Top 100/thermosets Chapter 2. molecular architecture

  20. TOP 100/ELASTOMERS Chapter 2. molecular architecture

  21. Top 100/elastomers Chapter 2. molecular architecture

  22. TOP 100/ADHESIVES Chapter 2. molecular architecture

  23. Top 100/adhesives Chapter 2. molecular architecture

  24. TOP 100/SPECIALTY Chapter 2. molecular architecture

  25. Top 100/specialty Chapter 2. molecular architecture

  26. Top 100/specialty Chapter 2. molecular architecture

  27. Top 100/specialty Chapter 2. molecular architecture

  28. Medical application example Citation data – one way to look for future trends SciFinder Scholar 1985 - 2005 WHERE’S THE ‘ACTION’ IN POLYMERS? Chapter 2. molecular architecture

  29. Medical applications are a rich applications area for polymers. Local variations in surface roughness at the nanoscale can induce strains in cell membranes, leading to the growth of F-actin stress fibers that span the length of the cell. W.E. Thomas, D. E. Discher, V. P. Shastri, Mechanical regulation of cells by materials and tissues, MRS Bulletin, 35 (2010), 578-583. POLYMER SCIENCE DIRECTIONS Chapter 1. Primer/introduction

  30. Cells feel their environment • Tissues are hydrated natural polymers with controlled elasticity • Most animals cells require adhesion to a solid to be viable • Tissue elasticity (~ kPa’s) is important for regulating cell growth, maturation and differentiation. Brain – 0.2 < E < 1 kPa; fat – 2 < E < 4 kPa; muscle – 9 < E < 15 kPa; cartilage – 20 < E < 25; bone – 30 < E < 40 kPa • Nanoroughness seems to affect a number of cell processes • 3D scaffolding is important • Mechanotransduction: cells adhere to surfaces via adhesive proteins attached to adaptor proteins, to the actomyosin cytoskeleton. Chapter 1. Primer/introduction

  31. There has been a major decline in publications on the physical properties of polymers, dropping from ~23% in 1985-9 to ~13% over the last two years. Plastics manufacturing, processing and fabrication has been relatively steady, but may have declined recently. Information on fundamental polymer chemistry seems to be nearly constant at 10% of the total. Information about pharmaceutical applications is increasing significantly, from 6% to ~12% recently. TOPICS 1-5 Chapter 2. molecular architecture

  32. Chapter 2. molecular architecture

  33. The synthetic high polymers category seems to be discontinued. Coatings and inks seem to be fairly steady at 2 %. There is significant growth in the areas of electric phenomena, optical, and radiation technology. These three areas together constitute ~11% of the current publication volume. TOPICS 6-10 Chapter 2. molecular architecture

  34. Chapter 2. molecular architecture

  35. There may be some renewed interest in the near term in photochemistry applications. Synthetic elastomers show some fluctuations, as do textiles and fibers. However, both surface chemistry + colloids, and biochemical methods show significant growth. TOPICS 11-15 Chapter 2. molecular architecture

  36. Chapter 2. molecular architecture

  37. Ceramics applications seem to be decline, despite that fact the ceramers are creating new interest. Cellulosics seems to be relatively steady, while general biochemistry is growing. The textile topic is now combined with fibers, and fossil fuel applications are dropping off dramatically. TOPICS 16-20 Chapter 2. molecular architecture

  38. Chapter 2. molecular architecture

  39. Chapter 2. molecular architecture

  40. Semiconductor industry Biomedical devices POLYMERS FOR SPECIFIC APPLICATION AREAS Chapter 2. molecular architecture

  41. Semiconductor industry • PolyBenzImidazole • Polyimide • PolyAmide-Imide • PolyEtherImide • PolyEtherEtherKetone • Polyphenylene Sulfide • Polyvinylidene Fluoride • Ethylene-ChloroTriFluoro-Ethylene • Ethylene-TetraFluoro-Ethylene • Polyethylene Terephthalate • Polyfluorene derivatives • Polymer transport layers: • Polyanaline (PANI) • Poly(3,4-ethylenedioxythiophene)/Poly(styrenesulfonate) [PEDOT-PSS] • Polypyrrole • Polythiophene • Polydiacetylene • Polyaryl ethers containing Perfluorocyclobutyl (PFCB) linkages; replacement for PMMA Chapter 2. molecular architecture

  42. Biomedical applications • Polyanhydrides • Polyphosphazenes • Polyurethanes • Polyvinylchloride (PVC) • Polyethylene (PE) • Polypropylene (PP) • Polymethylmethacrylate (PMMA) • Polystyrene (PS) • Polyester • Polyamide • Polyacetal • Polysulfone • Polycarbonate • Polysiloxane • Polylactide (PLA) • Polyglycolide (PGA) • Poly(glycolide-co-lactide); PLGA • Poly(dioxanone) • Poly(carbonate) Chapter 2. molecular architecture

  43. CARBON-CARBON BASED CHAINS Chapter 2. molecular architecture

  44. Poly(acrylic acid). PAA_2.avi Polyacrolein Polyacrylamide Polyacrylonitrile Poly(methyl methacrylate) Poly(2-hydroxyethyl methacrylate) POLYACRYLICS Chapter 2. molecular architecture

  45. Polyethylene Chlorinated polyethylene Polypropylene Poly(1-butene) Poly(isobutylene) Polystyrene Poly(2-vinyl pyridine) POLY(OLEFINS) Chapter 2. molecular architecture

  46. Poly(1,4-butadiene) BR (butadiene rubber) Polyisoprene NR (natural rubber) Polychloroprene CR, Neoprene Polynorbornene Poly(pentenamer) Ring-opening monomer POLYDIENES Chapter 2. molecular architecture

  47. Configurations for dienes Chapter 2. molecular architecture

  48. Lower costs than ethylene-based polymers Bond energies: C-F: 461 kJ/mol; C-H: 377 kJ/mol; C-Cl: 293 kJ/mol; C-Br: 251 kJ/mol; C-I: 188 kJ/mol PTFE + copolymers with hexafluoropropylene, perfluoropropylvinylether PTFCE PVC PVDF PVDC POLYHALOCARBONS Chapter 2. molecular architecture

  49. Poly(vinyl acetate)- inexpensive emulsion systems (paints) Poly(vinyl alcohol) - adhesives Poly(vinyl formal) -adhesives Poly(vinyl butyral) - adhesives Poly(vinyl methyl ether) – adhesives, plasticizers Poly(2-vinyl pyrrolidone) - OTHER VINYL POLYMERS Chapter 2. molecular architecture

  50. CARBON-NITROGEN CHAINS Chapter 2. molecular architecture

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