Introduction and Nomenclature

Abstract

The initial proof of the existence of very large organic molecules was supplied by Raoult [1] and van’t Hoff [2], who carried out cryoscopic molecular weight determinations on rubber, starch, and cellulose nitrate. By the methods developed by Raoult and by van’t Hoff and by the formulation of solution laws, molecular weights of 10,000–40,000 were demonstrated. Unfortunately, chemists of that day failed to appreciate this evidence and refused to accept it. The main reason for such a response was the inability to distinguish macromolecules from colloidal substances that could be obtained in low molecular weights. The opinion of the majority of that day was that “Raoul’s solution does not apply to materials in colloidal state.”

Appendices

Appendix

1.1.1 Additional Definitions:

Term	Definition
Tensile strength	Ability to resist stretching
Flexural strength	Resistance to breaking or snapping
Tensile stress (σ)	σ = force/cross-section area σ = F/A
Tensile strain (ε)	Change in sample length (when stretched) divided by the original length ε = Δl/l
Tensile modulus (E)	Ratio of stress to strain E = σ/ε

1.1.2 Recommended Reading

• R.B. Seymour, History of Polymer Science and Technology, Dekker, New York, 1982

• H. Morawetz, The Origin and Growth of a Science, Wiley-Interscience, New York, 1982

• M.P. Stevens, Polymer Chemistry, 3rd Ed., Oxford University Press, 1998, (Chapter 1)

• G. Odian, Principles of Polymerization, 3rd Ed. Wiley, New York, 1991, (Introduction)

Review Questions

1.2.1 Section 1.2

• 1. Define the degree of polymerization.

• 2. Polystyrene has a DP of 300. What is the molecular weight of the polymer?

• 3. What is a linear, a branched, a star-shaped, a comb-shaped, and a ladder polymer? Explain.

• 4. What is a network structure?

• 5. How can a network structure be formed by step-growth polymerization and also by chain-growth polymerization?

• 6. What is the difference between random and alternating copolymers?

• 7. What is meant by graft and block copolymers? Illustrate such copolymers of styrene and methyl methacrylate?

• 8. What are the important features of chain-growth and step-growth polymerizations. Explain the difference between the two? Can you suggest an analytical procedure to determine by what mechanism a particular polymerization reaction takes place?

• 9. What is the DP of polystyrene with molecular weight of 104,000 and poly(vinyl chloride) with molecular weight of 63,000?

• 10. Explain the differences between thermosetting and thermoplastic polymers and define gel point. How would you determine the gel point of a thermoset polymer?

• 11. Give the definitions of oligomer, telomer, and telechelic polymers.

• 12. What is a dendrimer polymer and what is a rotaxane polymer?

• 13. Illustrate three chain-growth polymers and three step-growth polymers.

1.2.2 Section 1.3

• 1. Name the following chain-growth polymers by the IUPAC system and by giving them trivial names:

1.2.3 Section 1.4

• 1. What is meant by tacticity?

• 2. Give a definition of and illustrate by examples on polystyrene, isotactic, syndiotactic, and atactic arrangement of the macromolecules. This should include Fischer and Newman projections.

• 3. Explain what is meant by erythrodiisotactic, threodiisotaactic polymers. Illustrate. Do the same for erythrodisyndiotactic and threodisyndiotactic.

• 4. What are tritactic polymers? Draw cis and trans tritactic polymers.