Page 290 - Carrahers_Polymer_Chemistry,_Eighth_Edition

Copolymerization 253

Dendrites: Complex molecules that are highly branched.
Domains: Sequences in a block copolymer or polymer.
Graft copolymer: Branched copolymer in which the backbone and the branches consist of
different mers.
Homopolymer: Macromolecule consisting of only one type of mer.
Hytrel: Trade name for a commercial TEP.
Ideal copolymer: Random copolymer.
Interpenetrating polymer network (IPN): Intimate combination of two polymers, both in net-
work form, where at least one of the two polymers is synthesized and or cross-linked in the
immediate presence of the other.
Ionomers: Copolymers typically containing mostly ethylene units, with the remaining units
being ion containing that are neutralized through reaction with metals.
Kraton: Trade name for an ABA block copolymer of styrene and butadiene.
Living polymers: Macrocarbanions.
Polyallomers: Block copolymers of ethylene and propylene.
Q-e scheme: A semiempirical method for predicting reactivity ratios.

Random copolymer: Copolymer in which there is no definite order for the sequence of the
different mers.
Reactivity ratio: Relative reactivity of one monomer compared to another monomer.
Saran: Trade name for copolymer of VC and vinylidene chloride.
SBR: Elastomer copolymer of styrene and butadiene.
Spandex: Elastic fiber consisting of a block copolymer of a polyurethane, hard segment, and

a polyester or polyether, soft segment.

Viscosity modifier: A polymer added to a solution that expands its effective length as tempera-
ture increases compensating for the effect that increased temperature has on decreasing
the viscosity.
Wall equation: Predecessor to the copolymer equation.

EXERCISES
1. Draw representative structures for (a) homopolymers, (b) alternation copolymers, (c) random
copolymers, (d) AB block copolymers, and (e) graft copolymers of styrene and acrylonitrile.
2. If equimolar quantities of M and M are used in an azeotropic copolymerization, what is the
1 2
composition of the feed after 50% of the copolymer has formed?
3. Defi ne r and r in terms of rate constants.
1 2
4. Do the r and r values increase or decrease during copolymerization?
1 2
5. What is the effect of temperature on r and r ?
1 2

6. What will be the composition of copolymers produced in the first part of the polymerization of
equimolar quantities of vinylidene chloride and VC?
7. What monomer may be polymerized by anionic, cationic, and free radical chain techniques?
8. Which chain-polymerization technique would you select to polymerize (a) isobutylene, (b) acry-
lonitrile, and (c) propylene?
9. If r r is about zero, what type of copolymer would be formed?
1 2
10. Show a structure for an AB block copolymer.
11. What is the value of r r for an ideal random copolymer?
1 2
12. Which would polymerize more readily?
Cl C
or
H C
2
Cl C
(a) (b)

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