Slide_ Polímeros ITA

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Vc consegue 
dizer quais 
polímeros estão 
aqui?
POLÍMEROS
Unidades 
básicas do 
polímero
Polímeros Macromoléculas formadas por monômeros
Muitas partes
2 X = X2
Monômero Dímero
2 NO2 = N2O4 Dimerização do NO23 X = X3
Monômero Trímero
Acetileno Benzeno
Trimerização 
do acetilenoPolímero
n X = [ X ]n
Homopolímeros e copolímeros
Mesmo monômero Monômeros diferentes
CLASSIFICAÇÃO
Termoplásticos x Termofixos (termoestáveis)
Podem ser 
remoldados 
com 
aquecimento
Não podem 
ser remoldados 
com 
aquecimento
Naturais x Sintéticos
Proteínas
Carboidratos
DNA, RNA
Borrachas
Demais
Não esqueça: a 
celulose também é 
um polímero!
PVC
Estereoquímica dos polímeros -Taticidade
Comportamento mecânico
Plásticos
Fibras
Borrachas (elastômeros) 
ADIÇÃO 
CONDENSAÇÃO
REARRANJO
Tipo de reação 
de polimerização
Polímeros de adição
Em geral são homopolímeros (mas podem ser copolímeros)
Em geral: C – C[ ]n
π
C = Cn
PVC
26-2 Addition Polymers 1225
Chain growth may continue with addition of several hundred or several thousand
styrene units. The length of a polymer chain depends on the number of additions of
monomers that occur before a termination step stops the process. Strong polymers with
high molecular weights result from conditions that favor fast chain growth and minimize
termination steps. Eventually the chain reaction stops, either by the coupling of two chains
or by reaction with an impurity (such as oxygen) or simply by running out of monomer.
P R O B L E M 26-1
Show the intermediate that would result if the growing chain added to the other end of the
styrene double bond. Explain why the final polymer has phenyl groups substituted on every
other carbon atom rather than randomly distributed.
Application: Bacterial Polymers
In the presence of limited nutrients,
bacteria can be induced to make polyhy-
droxybutyrates and valerates, which are
processed into a copolymer known as
Biopol™. Biopol™ has properties similar
to polypropylene, but it is biodegradable
and obtained from nonpetroleum sources.
C CO
O O
O C
H
HH
C
heat heat
C
H
H
H
C
benzoyl peroxide phenyl radicals styrene benzylic radical
(–CO2 )
C
H
H
growing chain
C C
H
H
H
C C
H
H
C
H H
H
elongated chain
C
H
H H
polystyrene
n = about 100 to 10,000
n
C
many more
styrene molecules
styrene
C
H
C
H
Chain Branching by Hydrogen Abstraction Low-density polyethylene is soft and
flimsy because it has a highly branched, amorphous structure. (High-density poly-
ethylene, discussed in Section 26-4, is much stronger because of the orderly structure
of unbranched linear polymer chains.) Chain branching in low-density polyethylene
results from abstraction of a hydrogen atom in the middle of a chain by the free radical
H
n
C
CH3
polypropylene
propylene
Cn H2 C CH CH3
H
H
benzoyl peroxide
high pressure
MECHANISM 26-1 Free-Radical Polymerization
Initiation step: The initiator forms a radical that reacts with the monomer to start the chain.
Propagation step: Another molecule of monomer adds to the chain.
Ethylene and propylene also polymerize by free-radical chain-growth polymeriza-
tion. With ethylene, the free-radical intermediates are less stable, so stronger reaction
conditions are required. Ethylene is commonly polymerized by free-radical initiators at
pressures around 3000 atm and temperatures of about 200 °C. The product, called low-
density polyethylene, is the material commonly used in stretchy polyethylene bags.
P R O B L E M 26-2
Propose a mechanism for reaction of the first three propylene units in the polymerization of
propylene in the presence of benzoyl peroxide.
POLIETILENO
PEAD PEBD
PEAD = HDPE e PEBD = LDPE
Estereoquímica dos polímeros -Taticidade
Menos resistente
Tg = temperatura de transição vítrea
Tm = temperatura de fusão
Curiosidade
1232 CHAPTER 26 Synthetic Polymers
Synthetic Rubber There are many different formulations for synthetic rubbers, but
the simplest is a polymer of buta-1,3-diene. Specialized Ziegler–Natta catalysts can
produce buta-1,3-diene polymers where 1,4-addition has occurred on each butadiene
unit and the remaining double bonds are all cis. This polymer has properties similar to
those of natural rubber, and it can be vulcanized in the same way.
Three or more monomers may combine to give polymers with desired properties.
For example, acrylonitrile, butadiene, and styrene are polymerized to give ABS plas-
tic, a strong, tough, and resilient material used for bumpers, crash helmets, and other
articles that must withstand heavy impacts.
1,4-polymerization of buta-1,3-diene
cis-1,4-polybutadiene
Overall reaction
H
H
H
Cl
C C
vinyl chloride
+
H
H
Cl
Cl
C C
vinylidene chloride
CH2 C
H
Cl
CH2 C
Cl
Cl
Saran®
n
P R O B L E M 26-12
(a) Isobutylene and isoprene copolymerize to give “butyl rubber.” Draw the structure of the
repeating unit in butyl rubber, assuming that the two monomers alternate.
(b) Styrene and butadiene copolymerize to form styrene-butadiene rubber (SBR) for pas-
senger tires. Draw the structure of the repeating unit in SBR, assuming that the two
monomers alternate.
Wallace Carothers, the inventor of
nylon, stretches a piece of synthetic
rubber in his laboratory at the
DuPont company.
P R O B L E M 26-11
(a) Draw the structure of gutta-percha, a natural rubber with all its double bonds in the trans
configuration.
(b) Suggest why gutta-percha is not very elastic, even after it is vulcanized.
All the polymers we have discussed are homopolymers, polymers made up of identical
monomer units. Many polymeric materials are copolymers, made by polymerizing two
or more different monomers together. In many cases, monomers are chosen so that they
add selectively in an alternating manner. For example, when a mixture of vinyl chloride
and vinylidene chloride (1,1-dichloroethylene) is induced to polymerize, the growing
chain preferentially adds the monomer that is not at the end of the chain. This selective
reaction gives the alternating copolymer Saran®, used as a film for wrapping food.
26-6
Copolymers of 
Two or More
Monomers
Condensation polymers result from formation of ester or amide linkages between difunc-
tional molecules. Condensation polymerization usually proceeds by step-growth poly-
merization, in which any two monomer molecules may react to form a dimer, and dimers
may condense to give tetramers, and so on. Each condensation is an individual step in
the growth of the polymer, and there is no chain reaction. Many kinds of condensation
polymers are known. We discuss the four most common types: polyamides, polyesters,
polycarbonates, and polyurethanes.
26-7
Condensation
Polymers
Filme “PVC"
COPOLÍMERO
] queima tem 
cheiro de vela
] queima tem 
cheiro adocicado
] queima libera 
gás tóxico
Um exemplo de polímero condutor de eletricidade
o trans - poli - acetileno
600 D e l o c a l i z e d P i S y s t e m sC H A P T E R 1 4
1,2-Dimethylenecyclohexane
Exercise 14-18
Formulate the products of [4 1 2]cycloaddition of tetracyanoethene with
(a) 1,3-butadiene; (b) cyclopentadiene; (c) 1,2-dimethylenecyclohexane (see margin).
The Diels-Alder reaction is concerted
The Diels-Alder reaction takes place in one step. Both new carbon–carbon single bonds 
and the new ! bond form simultaneously, just as the three ! bonds in the starting materi-
als break. As mentioned earlier (Section 6-4), one-step reactions, in which bond breaking 
happens at the same time as bond making, are concerted. The concerted nature of this 
transformation can be depicted in either of two ways: by a dotted circle, representing the 
six delocalized ! electrons, or by electron-pushing arrows. Just as six-electron cyclic overlap 
Can you imagine replacing all the copper wire in our electri-
cal power lines and appliances with an organic polymer? A 
giant step toward achieving this goal was made in the late1970s by Heeger, MacDiarmid, and Shirakawa,* for which 
they received the Nobel Prize in 2000. They synthesized a 
polymeric form of ethyne (acetylene) that conducts electric-
ity as metals do. This discovery caused a fundamental 
change in how organic polymers (“plastics”) were viewed. 
Indeed, normal plastics are used to insulate and protect us 
from electrical currents.
What is so special about polyethyne (polyacetylene)? For 
a material to be conductive, it has to have electrons that are 
free to move and sustain a current, instead of being localized, 
as in most organic compounds. In this chapter, we have seen 
how such delocalization is attained by linking sp2 hybridized 
carbon atoms in a growing chain: conjugated polyenes. We 
have also learned how a positive charge, a single electron, or 
a negative charge can “spread out” along the ! network, not 
REAL LIFE: MATERIALS 14-1 Organic Polyenes Conduct Electricity
unlike a molecular wire. Polyacetylene has such a polymeric 
structure, but the electrons are still too rigid to move with the 
facility required for conductivity. To achieve this goal, the 
electronic frame is “activated” by either removing electrons 
(oxidation) or adding them (reduction), a transformation 
called doping . The electron hole (positive charge) or electron 
pair (negative charge) delocalize over the polyenic structure 
in much the same way as that shown for extended allylic 
chains in Section 14-6. In the original breakthrough experi-
ment, polyacetylene, made from acetylene by transition 
metal-catalyzed polymerization (see Section 12-15), was 
doped with iodine, resulting in a spectacular 10-million-fold 
increase in conductivity. Later refi nement improved this 
fi gure to 1011, essentially organic copper!
*Professor Alan J. Heeger (b. 1936), University of California at Santa 
Barbara, California; Professor Alan G. MacDiarmid (1927–2007), 
University of Pennsylvania, Philadelphia, Pennsylvania; Professor 
Hideki Shirakawa (b. 1936), University of Tsukuba, Japan.
!
!
!
HHHH
HHHH
trans-Polyacetylene Conducting polyacetylene
!1e
"
"
"
Oxidation
(doping)
The black, shiny, fl exible foil of polyacetylene 
(polyethyne) made by polymerization of gaseous 
ethyne.
600 D e l o c a l i z e d P i S y s t e m sC H A P T E R 1 4
1,2-Dimethylenecyclohexane
Exercise 14-18
Formulate the products of [4 1 2]cycloaddition of tetracyanoethene with
(a) 1,3-butadiene; (b) cyclopentadiene; (c) 1,2-dimethylenecyclohexane (see margin).
The Diels-Alder reaction is concerted
The Diels-Alder reaction takes place in one step. Both new carbon–carbon single bonds 
and the new ! bond form simultaneously, just as the three ! bonds in the starting materi-
als break. As mentioned earlier (Section 6-4), one-step reactions, in which bond breaking 
happens at the same time as bond making, are concerted. The concerted nature of this 
transformation can be depicted in either of two ways: by a dotted circle, representing the 
six delocalized ! electrons, or by electron-pushing arrows. Just as six-electron cyclic overlap 
Can you imagine replacing all the copper wire in our electri-
cal power lines and appliances with an organic polymer? A 
giant step toward achieving this goal was made in the late 
1970s by Heeger, MacDiarmid, and Shirakawa,* for which 
they received the Nobel Prize in 2000. They synthesized a 
polymeric form of ethyne (acetylene) that conducts electric-
ity as metals do. This discovery caused a fundamental 
change in how organic polymers (“plastics”) were viewed. 
Indeed, normal plastics are used to insulate and protect us 
from electrical currents.
What is so special about polyethyne (polyacetylene)? For 
a material to be conductive, it has to have electrons that are 
free to move and sustain a current, instead of being localized, 
as in most organic compounds. In this chapter, we have seen 
how such delocalization is attained by linking sp2 hybridized 
carbon atoms in a growing chain: conjugated polyenes. We 
have also learned how a positive charge, a single electron, or 
a negative charge can “spread out” along the ! network, not 
REAL LIFE: MATERIALS 14-1 Organic Polyenes Conduct Electricity
unlike a molecular wire. Polyacetylene has such a polymeric 
structure, but the electrons are still too rigid to move with the 
facility required for conductivity. To achieve this goal, the 
electronic frame is “activated” by either removing electrons 
(oxidation) or adding them (reduction), a transformation 
called doping . The electron hole (positive charge) or electron 
pair (negative charge) delocalize over the polyenic structure 
in much the same way as that shown for extended allylic 
chains in Section 14-6. In the original breakthrough experi-
ment, polyacetylene, made from acetylene by transition 
metal-catalyzed polymerization (see Section 12-15), was 
doped with iodine, resulting in a spectacular 10-million-fold 
increase in conductivity. Later refi nement improved this 
fi gure to 1011, essentially organic copper!
*Professor Alan J. Heeger (b. 1936), University of California at Santa 
Barbara, California; Professor Alan G. MacDiarmid (1927–2007), 
University of Pennsylvania, Philadelphia, Pennsylvania; Professor 
Hideki Shirakawa (b. 1936), University of Tsukuba, Japan.
!
!
!
HHHH
HHHH
trans-Polyacetylene Conducting polyacetylene
!1e
"
"
"
Oxidation
(doping)
The black, shiny, fl exible foil of polyacetylene 
(polyethyne) made by polymerization of gaseous 
ethyne.
(Ita 2011) Assinale a opção que apresenta a 
fórmula molecular do polímero que pode 
conduzir corrente elétrica. 
a) –[-CH2 – CH2 –]-n 
b) –[-CH = CH–]-n 
c) –[-CF2 – CF2 –]-n 
d) –[-CHCH3 – CH2 –]-n 
e) –[-CHOH – CH2 –]-n 
Exercícios
EXTRA PVA = PoliVinilAcetato - usado em 
colas e tintas. Como produz?
E como produz: (alcool polivinílico)?
Poliacrilato de sódio Polímero das fraldas, absorventes, etc
26-5 Natural and Synthetic Rubbers 1231
The cis double bonds in natural rubber force it to assume a kinked conformation
that may be stretched and still return to its shorter, kinked structure when released.
Unfortunately, when we pull on a mass of natural rubber, the chains slide by each other
and the material pulls apart. This is why natural rubber is not suitable for uses requiring
strength or durability.
Vulcanization: Cross-Linking of Rubber In 1839, Charles Goodyear accidentally
dropped a mixture of natural rubber and sulfur onto a hot stove. He was surprised to
find that the rubber had become strong and elastic. This discovery led to the process
that Goodyear called vulcanization, after the Roman god of fire and the volcano.
Vulcanized rubber has much greater toughness and elasticity than natural rubber. It
withstands relatively high temperatures without softening, and it remains elastic and
flexible when cold.
Vulcanization also allows the casting of complicated shapes such as rubber tires.
Natural rubber is putty-like, and it is easily mixed with sulfur, formed around the tire
cord, and placed into a mold. The mold is closed and heated, and the gooey mass of string
and rubber is vulcanized into a strong, elastic tire carcass.
On a molecular level, vulcanization causes cross-linking of the cis-1,4-polyisoprene
chains through disulfide bonds, similar to the cystine bridges that link
peptides (Section 24-8C). In vulcanized rubber, the polymer chains are linked together
so they can no longer slip past each other. When the material is stressed, the chains
stretch, but cross-linking prevents tearing. When the stress is released, the chains return
to their shortened, kinked conformations as the rubber snaps back. Figure 26-4 shows
the structure of rubber before and after vulcanization.
Rubber can be prepared with a wide range of physical properties by controlling the
amount of sulfur used in vulcanization. Low-sulfur rubber, made with about 1 to 2%
sulfur, is soft and stretchy. It is good for rubber bands and inner tubes. Medium-
sulfur rubber(about 2 to 5% sulfur) is somewhat harder, but still flexible, making good
tires. High-sulfur rubber (10 to 30% sulfur) is called hard rubber and was once used
as a hard synthetic plastic. Using more sulfur in the mixture increases the number of
disulfide cross-links as well as the frequency of bridges containing three or more
sulfur atoms.
1¬ S ¬ S ¬ 2
Natural rubber
White latex drips out of cuts in the
bark of a rubber tree in a Malaysian
rubber plantation.
S
S S
heat
S
S
S S S
S
SS
S
S
FIGURE 26-4
Vulcanized rubber has disulfide
cross-links between the polyisoprene
chains. Cross-linking forms a
stronger, elastic material that does
not pull apart when it is stretched.
Isopreno (adição 1-4)
Polimerização da borracha - sintética (Buna)
Vulcanização
Borrachas sintéticas
Eritreno (buta-1,3-dieno)
Cloropreno
Eritreno + estireno
Buna
Neoprene
SBR (styrene - butadiene - 
rubber)
ABS = acrilonitrila+butadieno+estireno
(Ita 2012) Assinale a opção que indica o polímero da borracha natural. 
a) Poliestireno 
b) Poliisopreno 
c) Poli (metacrilato de metila) 
d) Polipropileno 
e) Poliuretano 
OBS.: O formol também pode formar um polímero de 
adição (usado em engrenagens). Escreva a reação.
Polímeros de condensação
Nylon
Em geral são copolímeros (mas também podem ser 
homopolímeros)
Alternativa para produzir Nylon
Nesse caso é um homopolímero!!
O Kevlar® é feito do 
ácido tereftálico e do 
p-diaminobenzeno.
Escreva a estrutura do 
Kevlar®
PET
Bom exemplo de 
homopolímero de 
condensação,
Escreva a reação de 
polimerização.
1236 CHAPTER 26 Synthetic Polymers
P R O B L E M 26-18
Propose a mechanism for the reaction of phenyl isocyanate with ethanol.
A polyurethane results when a diol reacts with a diisocyanate, a compound with two
isocyanate groups. The compound shown next, commonly called toluene diisocyanate,
is frequently used for making polyurethanes. When ethylene glycol or another diol is
added to toluene diisocyanate, a rapid condensation gives the polyurethane. Low-
boiling liquids such as butane are often added to the reaction mixture. Heat evolved
by the polymerization vaporizes the volatile liquid, producing bubbles that convert the
viscous polymer to a frothy mass of polyurethane foam.
CH3
N N
+
C OO C
toluene diisocyanate
HO CH2 CH2 OH
ethylene glycol
CH3
N N C O
O
C
H H
O
CH2 CH2 O
CH3
N N C O
O
C
a polyurethane
H H
O
CH2 CH2 O
n
R´OH+
carbamate ester
(urethane)
isocyanate alcohol
N C OR N C OH
O
R´R
P R O B L E M 26-19
Explain why the addition of a small amount of glycerol to the polymerization mixture gives a
stiffer urethane foam.
P R O B L E M 26-20
Give the structure of the polyurethane formed by the reaction of toluene diisocyanate with
bisphenol A.
Although polymers are very large molecules, we can explain their chemical and physi-
cal properties in terms of what we already know about smaller molecules. For exam-
ple, when you spill a base on your polyester slacks, the fabric is weakened because the
base hydrolyzes some of the ester linkages. The physical properties of polymers can also
be explained using concepts we have already encountered. Although polymers do not
crystallize or melt quite like smaller molecules, we can detect crystalline regions in a
26-8
Polymer Structure
and Properties
Example
N CH2 CH3C O +
phenyl isocyanate
OH
ethanol
N C O
ethyl-N-phenylcarbamate
H
O
CH2 CH3
Poliuretanas (polímero de rearranjo)
Podem ser espumas, sólidos isolantes, 
flexíveis (preservativos de poliuretano) etc. 
Silicones
R
e
p
ro
d
u
ç
ã
o
p
ro
ib
id
a
.
A
rt
.1
8
4
d
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C
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d
ig
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a
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e
i
9
.6
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1
9
d
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fe
v
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re
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d
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1
9
9
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.
394
6.4. Silicones
Os polímeros descritos até aqui são polímeros orgânicos, isto é, formados por C, H, O, N etc. Um
produto diferente, mas muito importante, são os silicones, cuja estrutura fundamental é:
Observe que se trata de um polímero linear, cuja cadeia (chamada de siloxano) é formada por
átomos de silício e de oxigênio alternados. Ao silício, ligam-se grupos orgânicos (R), que podem variar
CH3, CF3, C2H5, etc. , resultando então polímeros de propriedades muito diferentes.
As cadeias O Si O Si são comuns na Química Inorgânica, pois existem na areia, no
quartzo e nos silicatos.
Os silicones, contudo, devem ser considerados produtos intermediários entre a Química Inorgânica
e a Química Orgânica, já que apresentam ramificações orgânicas e propriedades que muito se asse-
melham aos polímeros orgânicos que estamos estudando. Também não se deve estranhar a possibili-
dade de ligação entre o silício e os grupos orgânicos. Afinal, o carbono e o silício pertencem à mesma
família da Classificação Periódica dos Elementos (grupo 14 ou coluna 4A) e, portanto, devem apre-
sentar propriedades semelhantes (por exemplo, existem os chamados silanos: SiH4; Si2H6 etc., seme-
lhantes aos alcanos).
O silicone foi inventado em 1943. Sua fabricação é feita pela seguinte seqüência de reações:
SiO O
R
R
Si O
R
R
Si O
R
R
Si
R
R
Cl Cl
CH3
CH3
Si
Dicloro-dimetil-silano
Si 2 CH3Cl1
Dependendo dos grupos orgânicos presentes e do menor ou maior tamanho das moléculas, o
silicone pode variar de líquido extremamente fluido, para graxa viscosa e, por fim, para um sólido
semelhante à borracha. Daí sua utilização em:
• fluidos dielétricos, hidráulicos; surfactantes; antiespumantes; desmoldantes usados em indús-
trias têxtil, farmacêutica, de cosméticos, de tintas, de equipamentos elétricos etc.;
• graxas, como lubrificante para temperaturas altas e baixas e para alto vácuo;
• resinas, para tintas resistentes ao tempo e à corrosão;
• plásticos, para equipamentos e implantes cirúrgicos, para a fabricação de adesivos e selantes (por
exemplo, a cola de silicone é usada na montagem de aquários residenciais e na vedação de janelas);
SiO2 (areia) 1 C Si 1 CO2
Calor
Cl2n H2O2nCl
CH3
CH3
Si 1 HCl4n1O O
CH3
CH3
Si
CH3
CH3
Si
n
Polidimetil-siloxano
Capitulo 17B-QF3-PNLEM 11/6/05, 12:56394
Dependendo do tamanho do grupo podem ser :
Fluidos
Graxas
Resinas
Colas
Borrachas Etc
(Ita 2012) Assinale a opção com a resina polimérica que mais 
reduz o coeficiente de atrito entre duas superfícies sólidas. 
a) Acrílica 
b) Epoxídica 
c) Estirênica 
d) Poliuretânica 
e) Poli (dimetil siloxano) 
(Ita 2015) Considere as seguintes comparações entre as 
respectivas temperaturas de fusão dos polímeros representados 
pelas suas unidades repetitivas: 
Assinale a opção que apresenta a(s) comparação(ões) ERRADA(S). 
a) Apenas I 
b) Apenas I e IV 
c) Apenas II e III 
d) Apenas III e IV 
e) Apenas IV 
E agora ?
BOA PROVA - BOM DESCANSO
ATÉ A REVISÃO