Page 587 - Carrahers_Polymer_Chemistry,_Eighth_Edition

550 Carraher’s Polymer Chemistry

3. Among the most important reactions on polymers are those that occur with biomacromole-
cules such as involved in the transfer of oxygen and the activity of enzymes. Shape, size, elec-
tronic configuration are all essential factors in the transfer of oxygen and activity of enzymes.

The transfer of oxygen can be mathematically described using the classical Michaelis–Menten
approach. The two major models describing the activity of nonallosteric enzymes such as
myoglobin are referred to as the lock-and-key model and the induced-fi t model. Hemoglobin
is an example of an allosteric enzyme where the two most popular models describing this
behavior are the concerted and sequential models.

GLOSSARY
Anchimeric reactions: Reactions enhanced by the presence of a neighboring group.
Chain scission: Breaking of a polymer chain.
Curing: Cross-linking producing a polymer network.
Cyclized rubber: Isomerized rubber containing cyclohexane rings.
Heme: Iron-containing active site for hemoglobin and myoglobin.
Hemoglobin: Allosteric enzyme responsible for the transport of oxygen in our bodies; con-
tains four myoglobin-like units.
Hydrogenation: Addition of hydrogen to an unsaturated compound.
Induced-fit model: One of two basic models employed to describe enzymatic behavior of

nonallosteric molecules. Here, the steps are similar to the lock-and-key model except the
reactants “induce” a change in the conformation ini the conformation of the active site
allowing the active site to bind with the reactant.
Kraton: Trade name for ABA block copolymer of styrene (A) and butadiene (B).
Kuhn element: Number of repeat units needed so that the most probable distance between the

first and the growing end is back at the first unit again.

Ladder polymer: Double-stranded polymer for added stability.
Lock-and key model: One of two basic models to describe the selectivity and catalytic nature
of nonallosteric enzymes. In this model the reactant(s) is attracted to the active site on the
enzyme, which is of the same general size, shape, and complementary electronic nature as
the reactant.
Macromolecular monomers (macromers): Polymers containing one reactive end group.
Myoglobin: Nonallosteric enzyme responsible for the storage of oxygen in our bodies. The
activity follows the kinetic scheme described by Michaelis–Menten.
Ozonolysis: Reaction of an unsaturated organic compound with ozone.
Photosynthesis: Metabolic pathway for the conversion of carbon dioxide into organic com-
pounds, mainly carbohydrates, using sunlight as the energy source.
Telechelic polymers: Polymers containing two active ends.
Telomerization: Abstraction of an atom by a macroradical.
Topochemical reactions: Reactions on the surface.

EXERCISES
1. In general, which metal ions are better chelated by polymers such as the salt of poly(acrylic acid)?
2. What is the general mechanism for the curing of step-reaction polymers?
3. Write the formula for perdeuterated PE.
4. What is the major difference between reactions occurring on benzene and polystyrene.
5. When would you expect a polymer to undergo degradation via random scission?
6. How might you cross-link a PE coating after it is applied to a wire?
7. How might you prepare a block copolymer of styrene and an alternating copolymer of ethylene
and propylene?

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