Direct Measurement of Interaction Forces between Microsphere Particle and Polyelectrolyte Brush using Total Internal Reflection Microscope (TIRM)

Introduction to Synthetic Polymers in Modern Life

• Presenter: To Ngai, Department of Chemistry, The Chinese University of Hong Kong
• Contact: [email protected]
• Concepts:
  • Polymers are large molecules composed of long chains of atoms covalently bonded.
  • Both natural and synthetic polymers play a crucial role in life and industry.

Natural vs. Synthetic Polymers

• Natural Polymers:
  • Proteins, DNA, RNA
  • Polysaccharides (e.g., cellulose in plants and animals)
• Synthetic Polymers:
  • Polystyrene, polyethylene, poly(vinyl chloride)
  • Polyesters, polyurethane

Basics and History of Polymers

• Purpose: Initially created as substitutes for natural materials or to improve them.
• Key Figures:
  • Hermann Staudinger (1920): Father of Modern Polymer Chemistry.
  • Wallace Hume Carothers (1930s): Father of Synthetic Polymer Science.
• Significant Developments:
  • Staudinger's Nobel Prize in 1953 for Polymer Chemistry.

Commercialization of Polymers

• Key Polymers and Their Development:
  • Polystyrene (1929/1930)
  • Nylon 66 (1939)
  • Polyethylene (1939)
• Economic Impact:
  • Over 100 billion pounds of synthetic polymers produced annually in the U.S.
  • $20 billion net favoring exports in the U.S.

Classification of Polymers

• Thermal Response:
  • Thermoplastics: Melt when heated, resolidify when cooled.
  • Thermoset: Do not melt upon heating; decompose at high temperatures.
• Chemical Reaction:
  • Addition Polymers: Formed by the addition reaction of unsaturated monomers.
  • Condensation Polymers: Formed by the loss of a small molecule during polymerization.

Polymer Architectures and Properties

• Examples:
  • The properties of polymers vary based on their chemical composition and molecular structure.
• Big Six Plastics:
  • Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Teflon, Poly(ethylene terephthalate) (PET), Kevlar

Specific Polymers

Polyethylene (PE)

• Discovered in 1933; applications include film, packing, containers, and pipes.
• Types:
  • Low Density Polyethylene (LDPE): Stretchy, transparent.
  • High Density Polyethylene (HDPE): Opaque, rigid, strong.

Polypropylene (PP)

• Similar to ethylene, polymerized using Ziegler-Natta catalysts.
• Applications: Kitchenware, car bumpers, CD cases.

Polystyrene (PS)

• Entered market in 1930, notable for transparency, thermal stability, and low cost.
• Forms: Standard PS, Expanded PS (foam), High Impact PS (HIP).

Teflon

• Trade name for poly(tetrafluoroethylene) (PTFE), known for extreme chemical resistance and thermal stability.

Poly(ethylene terephthalate) (PET)

• Known as Dacron, used extensively in bottles for drinks.
• Advantages include clarity, air-tightness, and lightweight compared to glass.

Kevlar

• Discovered in 1965, known for high strength and lightweight properties.
• Applications: Body armor, racing cars, industrial uses.

Environmental and Economic Considerations

• Challenges:
  • Limited petroleum resources for monomer production.
  • Low recycling rates for plastics.
• Innovations:
  • Use of renewable resources for polymer production (e.g., sugar-based polyethylene).
  • Development of biodegradable polymers like Polylactic Acid (PLA) from renewable resources.

Conclusion

• Synthetic polymers have revolutionized modern living with a wide array of applications.
• Future advancements require collaboration across disciplines to address environmental impacts.

References

1. Emsley, J. Molecules at An Exhibition: Portraits of Intriguing Materials in Everyday Life, Oxford University Press, Oxford, UK, 1998, pp116-145.
2. Eubanks, L. P., Middlecamp, C. H., Heltzel, C. E., Keller, S. W. Chemistry in Context: Applying Chemistry to Society, 6th Ed., McGraw-Hill, New York, 2009, Chapter 9, pp368-403.