BASIC TYPES OF POLYMERIZATIONS Flashcards
(192 cards)
1
Q
a process through
which a large number of monomer
molecules react together to form a
polymer
A
Polymerization
2
Q
The macromolecules
produced from a polymerization may
have a _______________ structure.
A
linear or a branched
3
Q
In _______, W. H. Carothers suggested a
classification of polymers into two
groups
A
1929
condensation (step-growth)
and addition (chain-growth) polymers
4
Q
a process by which monomer
units are attached one at a time in chainlike
fashion to form a linear molecule
A
Chain-growth polymerization or addition
polymerization
5
Q
In chain-growth polymerization or addition
polymerization, the composition
of the resultant product molecule is __________ of that of the original reactant monomer.
A
an exact
multiple
6
Q
growth of a polymer chain proceeds exclusively by
reaction(s) between **monomer(s) and reactive
site(s) **on the polymer chain with regeneration of
the reactive site(s) at the end of each growth step
A
chain reaction
7
Q
Chain-growth polymerization involves the addition of __________ to a rapidly growing chain
A
unsaturated
molecules
8
Q
The most common unsaturated compounds that undergo chain-growth polymerization are
A
olefins
9
Q
chain growth olefins, vinyl monomer example
A
image5
10
Q
Chain-growth polymerization is a polymerization
technique where unsaturated monomer molecules
add onto the ________on a growing polymer chain ____________.
A
active site , one at a time
11
Q
There are a ________ number of these
active sites at any moment during the polymerization which gives this method its key characteristics
A
limited
12
Q
The growing polymer in chain-growth polymerization is a __________, and polymerization proceeds via ___________
A
free radical, chain
mechanism.
13
Q
It is induced by the addition of ________________ or by ionic initiators.
A
-freeradical-forming reagents
14
Q
It involves three fundamental steps
A
initiation,
propagation, and termination.
15
Q
Growth centers can either be _____________________ in nature—
depending on the kind of initiator
system used.
A
ionic
(cationic or anionic), free radical,
or coordinational
16
Q
Based on the nature of the growth centers, chaingrowth polymerization is further
classified as
A
- Free-Radical polymerization
- Cationic polymerization
- Anionic polymerization
- Coordination or stereoregular
polymerization
17
Q
A chain
polymerization in which the
kinetic
-chain carriers are
radicals.
A
Free Radical
Polymerization
18
Q
a method of
polymerization by which a
polymer forms by the successive
addition of free
-radical building
blocks (repeat units).
A
➢ Free
-radical polymerization
19
Q
can be formed by
a number of different
mechanisms, usually involving
separate initiator molecules
A
Free radicals
20
Q
1st step in free-radical polymerization wherein there is an active monomer
A
❑ Initiation
21
Q
2ndstep in free-radical polymerization wherein there is a growth of the active
(free-radical) chain by sequential
addition of monomers
A
❑ Propagation
22
Q
3rd step in free-radical polymerization wherein active chain give
the final polymer product.
A
❑ Termination
23
Q
involves the acquisition of an
active site by the monomer
A
Initiation
24
Q
This may occur spontaneously by the** absorption of
heat, light (ultraviolet and visible), redox
reagents, electricity, high-energy
radiation, etc. that is any process that
creates the essential free radicals.**
A
Initiation
25
initiation of free-radical
polymerization is brought about by the
addition of small quantities of
compounds called
initiators
26
Typical initiators include
peroxides, azo
compounds, Lewis acids, and organometallic
reagents
27
usually a **weak organic compound **
that can be **decomposed thermally** or **by
irradiation** to produce free radicals, which are
molecules containing atoms with **unpaired
electrons.**
initiator
28
example of organic
compounds that can be decomposed thermally
to produce free radicals.
Dialkyl peroxides (ROOR)
diacylperoxides (RCO-O-O-CO-R)
hydroperoxides (ROOH)
azo compound (RN>NR)
29
example of commonly used free-radical
initiator
Benzoyl peroxide azobisisobutyronitrile
dit-butylperoxide
30
Initiation in a free-radical polymerization consists of two steps
1. dissociation of the initiator to form two radical species
2. addition of a single monomer molecule to the initiating radical (the association step).
31
On heating, benzoyl peroxide decomposes to give
two free
radicals
(image 11)
32
(image 11)
what is the active site
the electrons in the oxygen–oxygen bond are unpaired and become the
active site.
33
R representing a generalized ____________, the free radical can
be written R
organic chemical group
34
initiation step usually includes the addition of the ___________________
first monomer molecule
35
In this initiation reaction the free radical attacks the monomer and adds to it. The double bond is
__________, and the _________ reappears at the far end
broken open , free radical
36
Chain initiation involves the __________ of a radical initiator molecule (I) which is
easily dissociated by heat or light into two free radicals (2 R°).
Each radical R°
then adds a first monomer molecule (M) to start a chain which terminates with a
monomer activated by the presence of an ____________ (RM1°).
I → 2 R°
R° + M → RM1°
dissociation , unpaired electron
36
Involves the linear
growth of the polymer chain by
the sequential addition of
monomer units to this active
growing chain molecule
Propagation
37
On the addition of each monomer,
the free radical moves to the
end
of the chain.
38
Chain growth is relatively rapid;
the period required to grow a
molecule consisting of say , __________
repeat units in on the order of ____________ s.
1000 , 10-2
to 10-3
39
a reaction of an active center on the
growing polymer molecule, which
**adds one monomer molecule** to
form a new polymer molecule
(RM1°) **one repeat unit longer**.
Propagation
40
RM1° + M → RM2°
RMn° + M → RMn+1°
Propagation
41
**active center **remains an atom with
an **unpaired electron**.
The addition of the second monomer and a
typical later addition step
radical polymerization
42
due to annihilation of the radical center of the propagating chain.
Termination
43
The termination step involves the reaction of any two free radicals with each other, either by
combination or disproportionation.
44
Two propagating chains are terminated when two radicals combine to form an electron-pair (covalent) bond
combination (or coupling)
45
reaction of the unpaired electrons of two chains to
form a covalent bond between them
Combination
46
product is a single polymer
molecule with the combined length of
the two reactant chains:
RMn° + RMm°→ Pn+m
Combination
47
A pair of radicals can form two new molecules
disproportionation
48
a disproportionation termination step involves two growing molecules that react to from
two
“dead chains”
49
complicated step in which two growing polymer
chains are rendered inactive.
a disproportionation
50
transfer of a hydrogen atom from one chain to the
other, so that the two product chain
molecules are **unchanged in length **but
are **no longer free radicals**
RMn° + RMm° → Pn + Pm
Disproportionation
51
a growing polymer chain is deactivated or terminated
by transferring its growth activity to a previously inactive species
Chain Transfer
52
additional step usually involved in a free-radical polymerization
Chain Transfer
53
a step in which the growing polymer chain RMn°
takes an atom X from an inactive molecule XY, terminating the growth of the polymer chain
RMn° + XY → RMnX + Y°.
Chain transfer
54
RMn° + XY → RMnX + Y°.
The Y fragment ls a __________ which adds more monomer M
to form a new growing chain YMn°
new active center
55
can be categorized according to the nature
of the growing polymer centers, which yields the classifications
cationic polymerization and anionic polymerization.
Ionic polymerization
56
involve chain carriers or reactive centers that
are organic ions or charged organic groups
Ionic polymerization
57
an
ionic polymerization in which the kinetic-chain
carriers are cations.
Cationic polymerization
58
___________ is a type of chain growth
polymerization in which a cationic initiator transfers
charge to a monomer, which then becomes _______________. This reactive monomer goes on to react similarly with other monomers to form a polymer.
Cationic polymerization , reactive
59
The types of monomers necessary for cationic
polymerization are limited to __________ with ________________
alkenes , electrondonating substituents and heterocycles.
60
The growth center in this class of ionic
polymerizations is cationic in nature.
Cationic
Polymerization
61
polymer cation adds on the monomer
molecules to it sequentially, just as the
polymer radical adds on the monomer in
radical polymerization.
Cationic
Polymerization
62
**a true
catalyst** that is restored at the end of the
polymerization and does not become
incorporated into the terminated polymer
chain
Cationic
Polymerization
63
The initiation of the polymerization is accomplished by catalysts that are _________________.
proton donors (e.g.,protonic acids such as H2SO4)
64
Typical catalysts that are effective for cationic
polymerization include
AlCl3
AlBr3
BF3
TiCl4
SnCl4
sometimes H2SO4
65
exception of H2SO4,
these compounds are all _________________.
Lewis acids with strong
electron-acceptor capability
66
To be effective, H2SO4 (lewis acids) catalysts generally require the presence of a Lewis base such as water, alcohol, or acetic acid as a __________
cocatalyst.
67
The monomer molecules act like _____________ and react with the catalyst, giving rise to polymer ions.
electron donors
68
The successive addition of the monomer to the polymer ion is the
propagation reaction
69
Monomers that polymerize readily with these catalysts include
isobutylene
styrene
α-methylstyrene
vinyl alkyl ethers.
70
Cationic polymerizations proceed at _______________
.
high rates at low temperatures.
71
For example, the polymerization at –100°C of **isobutylene** with **BF3 or
AlCl3 as catalysts** yields, within a few seconds, a polymer with _______________________
molecular weight as high as 10^6
72
polymerization of isobutylene with BF3 as the
catalyst procedure
(image 28 & 29)
- Boron Triflouride (catalyst) react with Water (cocatalyst) to produce Catalystcocatalyst
complex
- Catalystcocatalyst complex react with isobutylene
- Isobutylene carbonium ion produced with gegen ion (Catalystcocatalyst complex without H+ outside)
73
Termination occurs either by ______________ to yield a polymer molecule with an unsaturated terminal unit and the original complex or through __________.
rearrangement of the ion pair
transfer to a monomer
74
in
which the kinetic
-chain carriers are anion
An ionic polymerization
75
a form of chain-growth polymerization or addition
polymerization that involves the
polymerization of monomers initiated with
anions.
An ionic polymerization
76
Anionic polymerizations are chain
-growth
processes in which the active center to which
successive monomers are added is a __________ that is associated with a ________________
negative ion
positive counterion
77
The _________________ between the
macromolecular anion and its counterion
depends on the **nature of the respective ions** and the **medium in which the polymerization is proceeding**
degree of interaction
78
While initiators for anionic polymerization are all _________ of varying base strengths, the initiator type required for a particular polymerization **depends on the ease** with which an anion can be formed from the monomer
electron donors
79
The initiator in an anionic polymerization may be any ____________, including **Grignard reagents** and other ________________ like n-butyl (n-C4H4) lithium
strong nucleophile
organometallic compounds
80
In general, the **strength of the base** required to i**nitiate polymerization** ______________ with increasing electronegativity of the
substituent on the monomer
decreases
81
commonly used initiator systems
for anionic polymerization
1. Alkali metals and alkali metal complexes (Na, K, Li, and their stable complexes with
aromatic compounds, liquid ammonia, or
ethers
2. Organometallic compounds (butyl lithium,
boron alkyl, tetraethyl lead, Grignard reagent)
3. Lewis bases (ammonia, triphenyl methane,
xanthene, aniline)
4. High-energy radiation
82
initiate polymerization by transfer of
an electron to the **double bond**
of the monomer
Alkali metals and alkali metal
complexes
83
83
84
Initiation by** direct attack **on the
alkali metal involves transfer of
the ____________ from
a **Group IA metal atom** to the
monomer. A radical ion (i.e., a
species having both ionic and
radical centers) is formed
loosely helds electron
85
The radical ion may dimerize to give a dianion
Initiation in Anionic Polymerization
86
The initiation process making dianion results in a _____________ capable of propagating at both of its ends
bifunctional dicarbanion
species
87
Initiation by organometallic compounds
and Lewis bases occurs by a _____________
of these compounds on the double bond
of the monomer molecule.
direct attack
88
Before the Lewis base can attack the
monomer, it must _________, and only then can
a carbanion be formed.
ionize
89
Anionic propagation is generally much ________
than free-radical reactions
faster
90
Propagation in anionic addition polymerization
results in the __________________ of
monomer.
complete consumption
91
If the starting reagents are **pure** and if the
polymerization reactor is **purged of all oxygen **and **traces of water**, propagation can
proceed indefinitely or until all monomer are consumed.
92
anionic polymerization proceed indefinitely or until all monomer are consumed
“living” polymerization.
93
most important group of initiators in Coordination Polymerization
Ziegler-Natta catalysts
94
In polymerizations of this type, each monomer is **inserted between the growing macromolecule and the initiator.**
Coordination Polymerization
95
Complexing of the monomer to the initiator frequently precedes the **insertion process **and this polymerization
coordination polymerization.
96
The field of coordination polymerization
originated in the __________ with the
pioneering works of ______________________
mid-1950s ,
Karl Ziegler in
Germany and Giulio Natta in Italy
97
Karl Ziegler discovered in the early 1950s that a **combination of aluminum alkyls** with certain ______________________ such as TiCl4 or VCl4
generated complexes that would polymerize
_______________ at low temperatures and pressures,
producing ______________ with an essentially linear
structure, now referred to as ________________________
transition metal compounds
ethylene
polyethylene
high-density polyethylene (HDPE)
98
Giulio Natta’s work led to the
recognition that the catalytic complexes described
by Ziegler were capable of polymerizing _____________
(commonly known as ___________ in the chemical
industry) to yield stereoregular polymers.
1-alkenes
alpha olefins
99
Many polymers are now manufactured on a commercial scale using Ziegler-Natta catalysts, the most prominent among them being ________________ of high molecular weight.
stereoregular (isotactic)
polypropylene
100
Since the Ziegler-Natta catalyst systems appear to
function via formation of a **coordination complex ** between the **catalyst, growing chain**, and **incoming monomer**, the process is also referred to as
________________ and the catalysts as __________________
coordination addition polymerization
coordination catalysts
101
arises because of order in the
spatial structures of polymer chains.
Stereoregularity
101
Ziegler–Natta catalyst systems consist of a mixture of the following two classes of compounds:
1. Compounds (normally **halides**) of transition elements of **groups IV to VIII **called catalyst ( TiCl3, TiCl4, VCl4, e, ZrCl4)
2. Compounds (**hydrides, alkyls, or aryls**) of elements of **groups I to IV**, called cocatalysts (Al(C2H5)3, Al(i-C4H9)3)
102
Coordination Polymerization ordered spatial structures are determined by two
phenomena.
- During the polymerization step the monomer
units are** joined together in a regular sequence ** determined by the **catalyst** used and by the polymerization conditions. Regularity of this type cannot be altered or changed during subsequent physical treatment of the polymer.
- Subsequently these regularly constructed
polymer chains **spontaneously arrange
themselves** into helical structures
103
Coordination
Polymerization -
Mechanism 3 types
(image 43)
isotactic
syndiotactic
atactic
104
Each polymer molecule __________ in size at a rapid
rate once its growth has been started. When the
macromolecule stops growing it ____________ generally
react with more monomers
increases , cannot
105
Growth of polymer molecules is caused by a _____________________
kinetic
chain of reactions.
106
Chain-growth polymerization involves the reaction
of _________________ that may be **free
radicals, ions, or polymer-catalyst bonds**
monomers with active centers
107
In ______________ polymerizations the **mechanisms
and rates of the reactions** that initiate, continue, and terminate polymer growth are _____________
chain-growth , different.
108
Chain-growth polymerization is usually
initiated by some _______________ and
the reaction is allowed to proceed under
conditions in which monomers ____________ react
with each other without the intervention of
an active center.
external source (energy,
highly reactive compound, or catalyst)
cannot
109
Polymers made by chain-growth reactions
are often ____________ by Carothers’s
definition. The most common polymers
made by these processes have only ____________ in their backbones.
addition polymers
carboncarbon links
110
refers to a type of polymerization mechanism in
which **bi-functional or multifunctional
monomers **react to form** first dimers**, then
**trimers**, longer oligomers and eventually
long chain polymers.
Step-growth polymerization
111
Many naturally-occurring and some
synthetic polymers are produced by
Step-growth polymerization
112
polyesters,
polyamides, polyurethanes, etc.example of
Step-growth polymerization
113
its** interlinking capacity**, or the
number of sites it has available for
**bonding with other molecules **under the
specific polymerization conditions.
functionality
114
A molecule may be classified as
______________________ depending on whether it
has one, two, or greater than two sites
available for linking with other
molecules.
monofunctional, bifunctional, or
polyfunctional
115
In step-growth polymerization, the **stepwise
reaction **occurs between pairs of _____________________ on the **reacting
molecule**s.
chemically
reactive or functional groups
116
There is usually a **low-molecular-weight **byproduct such as water that is eliminated (or
condensed)
STEP-GROWTH
POLYMERIZATION
117
**No reactant species has the chemical formula** of the repeat unit, and the **intermolecular reaction** occurs every time a repeat unit is formed.
STEP-GROWTH
POLYMERIZATION
118
Each step may consist of a combination of two
polymers having a **different or the same length **to form a** longer-length molecule.**
STEP-GROWTH
POLYMERIZATION
119
In a step-growth polymerization, the molecular weight of the polymer chain builds
up ____________ and there is __________reaction mechanism for the formation of polymer
slowly , only one
120
The polymerization reaction proceeds by **individual reactions** of the **functional
groups** on the monomers.
STEP-GROWTH POLYMERIZATION
121
two monomers react to form a dimer
Monomer + Monomer = Dimer +H2O
STEP-GROWTH POLYMERIZATION
(1st step)
122
The dimer may now react with another dimer to produce a tetramer, or the dimer
may react with more monomer to form a trimer
Monomer + Dimer = Trimer +H2O
Dimer + Dimer = Tetramer + H2O
STEP-GROWTH POLYMERIZATION (2nd step so on)
123
Any two species in the reaction mixture can react with
each other.
STEP-GROWTH POLYMERIZATION
124
expressed by n-mer +m-mer = (n+m)-mer
Step polymerization
(n and m from 1- large number)
125
reaction between dimethyl terephthalate and ethylene glycol to form a
linear poly(ethylene terephthalate) or
PET molecule with methyl alcohol as a by-product
126
Small molecule is eliminated at each step
Polycondensation
127
The structural unit in step-growth polymers is __________________ to the structure of the starting
monomer(s).
not
identical chemically
128
Step-growth polymers derive their names from
the __________________ involved in the polymerization process.
reactive type (characteristic interunit linkage)
129
In the reaction between the glycol and
dicarboxylic acid, the resulting
polymer is a ___________, in consonance with the
general name of reactions between ____________________
polyester
hydroxyl groups (–OH) and carboxylic cid groups (–COOH)
130
Monomers react without the elimination of a small molecule.
Polyaddition
131
______________ form a large class of
commercially important
polymers.
Polyesters
132
A typical polyester
is ______________________ the largest volume
synthetic fiber. It is also used
as ______________ and in bottle
applications.
poly(ethylene terephthalate)
(PETP)
film (mylar)
133
s are a special class of polyesters derived from carbonic acid (image 56)
Polycarbonates
134
second largest by volume engineering thermoplastics next
to polyamides.
Polycarbonates
135
Polycarbonates preparation involves the linking together of _______________ ,
by reacting them with a derivative of carbonic acid such as ____________________________
aromatic dihydroxy compounds (2,2-bis(4-hydroxyphenyl) propane or bisphenol A)
phosgene or diphenyl carbonate
136
characterized by the
presence of amide linkages (–CONH–) on the polymer main chain.
Polyamides, or nylons
137
a large number of polyamides can be synthesized based on four main synthetic routes
(1) **condensation reaction** between a dicarboxylic acid and a diamine,
(2) **reaction** between a diacid chloride and a diamine,
(3) **dehydration–condensation **reactions of amino acids
(4)** ring-opening polymerization** of
lactams.
138
nylons may be divided into two categories
based on synthetic routes (1) and (2)
based on routes (3) and (4).
139
are condensation polymers obtained from the reaction of **dianhydrides with diamine**s.
Polyimides
140
synthesized generally from **aromatic dianhydrides** and** aliphatic diamines**
Polyimides
141
from the reaction of **aromatic dianhydrides **with** aromatic diamines**.
aromatic polyimides
142
families of synthetic heterocycles with a wide
range of applications due to their physical and
chemical properties
Polybenzimidazoles and
Polybenzoxazoles
143
These **man-made molecules** are commonly used in **medicinal, agricultural, and environmenta**l areas due to their **ability to form strong metallic complexes **and their unique thermal and electrical
properties.
Polybenzimidazoles and
Polybenzoxazoles
144
also known as ladder
polymers or linker polymers
Aromatic ladder polymers,
145
type of polymer that consists of repeating units connected by **aromatic linkers**, such as benzene rings.
Aromatic ladder polymers,
146
popular for their **versatility **and
can be used in a variety of applications, including
**coatings, adhesives, and membranes.**
Aromatic Ladder Polymers
147
Ladder polymers are designed to have ____________________ and _____________________,
which makes them resistant to **heat and degradation.**
high
molecular weights and high melting temperatures
148
employed in the production of **aminoplasts and phenoplasts**, which are two different but related classes of thermoset polymers.
Formaldehyde
149
aminoplasts and phenoplasts
thermoset polymers
150
are products of the condensation reaction between either **urea** (urea–formaldehyde or UF resins) or** melamine** (melamine–formaldehyde or MF resins) with formaldehyde.
Aminoplasts
151
are prepared from the condensation products of **phenol or resorcinol and formaldehyde**
Phenoplasts or phenolic (phenol–formaldehyde or PF)
152
are polymers consisting of monomers joined together by ether linkages (two carbon atoms bonded to an oxygen atom).
Polyethers
153
example of Polyethers
elastomers
154
The structures of the Polyethers compounds vary
significantly, yet they all preserve the ____________.
C—O—C
connection
155
Polyethers can be either _____________ polyethers.
aliphatic or
aromatic
156
closely related to polyethers in
structure and properties
Polysulfides
157
Polysulfides also known as
Aromatic polythioethers
158
A typical aromatic polysulfide is _____________ which is used as electrical insulators and structural parts in the building of engines and vehicles.
poly(phenylene sulfide)
(PPS),
159
is prepared by the condensation
reaction between **p-dichlorobenzene and sodium sulfide**
Poly(phenylene sulfide)
160
Another family of linear aromatic
polymers which are tough, high-temperature-resistant engineering thermoplastics.
Polysulfones
161
Polysulfones may be synthesized by
the nucleophilic substitution of ________________ with activated ___________________.
alkali salts of biphenates
aromatic dihalides
162
A polysulfone from the reaction of **disodium salt of
bisphenol A** with **dichlorodiphenyl sulfone**
preparation
of bisphenol
163
In STEP-GROWTH, Monomers bearing _______________________ undergo step
polymerization.
functional groups such as
-OH, -COOH, -NH2, -NCO, etc.,
164
# ```
```
In chain growth, Monomers with ____________________
undergo polymerization when an active center
is formed.
carbon-carbon unsaturation
165
In step-growth , the growth of polymer molecules proceeds
by a ______________________________ , normally with the elimination of small molecules as by-products of condensation, such as H2O, HCl, NH3, etc., in each step.
stepwise intermolecular reaction (at a
relatively slow rate
166
The molecule never stops growing during polymerization.
STEP-GROWTH
167
Any two molecular species present can react.
STEP-GROWTH
168
In chain growth. each polymer molecule/chain ____________ once its growth has been
started by formation of an active center.
increases in size at a rapid rate
169
When the macromolecule stops growing (due to
termination reaction) it can generally not react
with more monomers (barring side reactions)
CHAIN-GROWTH
170
Only growth reaction adds repeating unit one
at a time of the chain.
CHAIN-GROWTH
171
In STEP-GROWTH, Monomer units _______react with each other or with polymers of any size.
can
172
Growth occurs in a _____________ and starts as the reactive species of a monomer or polymer encounters other species with which it can form a link.
series of fits
173
This can occur even in the absence of an added catalyst
STEP-GROWTH
174
In **chain growth of a polymer** molecule is caused by
a **kinetic chain of reactions** involving **rapid
addition of monomer** to an active center that
may be a _______________________
free radical, ion, or polymer-catalyst
bond.
175
The active center is produced by some
external source (energy, highly reactive
compound, or catalyst)
CHAIN-GROWTH
176
At any moment the reaction mixture essentially
consists of **full-grown**,** large polymer molecules,** **unreacted monomer molecules, and a very low concentration** (10-8- 10-3 mol L-1) of growing chains (i.e., possessing an active center) of **intermediate sizes**
CHAIN-GROWTH
177
In STEP-GROWTH, backbone of polymer chains contains
________________________ at **regular
intervals **due to condensed interunit links.
heteroatoms such as N, O, S, etc.,
178
In chain growth, usually the backbone of polymer chains consists
of_____________ and other kinds of
atoms such as O, N, S, etc., may appear in the
**side groups**
-C-C- linkages
179
A polymerization in which a **cyclic monomer yields a monomeric unit** which is **acyclic** or contains **fewer cycles** than the
monomer.
RING-OPENING POLYMERIZATION
180
Ring-opening polymerization (ROP) is a form of chain-growth polymerization in which the** terminus of a polymer chain attacks** ___________ to form a longer polymer. The reactive center can
**be radical, anionic or cationic.**
cyclic monomers
181
method where cylic monomers are
opened up to make extended chain
structures.
RING-OPENING POLYMERIZATION
182
The RING-OPENING POLYMERIZATION reaction is typically
driven by the release of
ring strain
183
example of ringopening of cyclic organic
compounds
epoxides
- ethylene
- propylene oxides
- epichlorohydrin
other cyclic ethers
- trioxane
- tetrahydrofuran.
Other important systems include
- cyclic esters (lactones)
- cyclic amides (lactams)
- cycloolefins
- siloxane.
184
Major applications of polymers
obtained from ring-opening
polymerization are in
coatings
fibers
elastomers
adhesives
thermoplastics
thermoset-based composite system
185
RING-OPENING
POLYMERIZATION
1. initial ring-opening of the cyclic monomer
2. polyaddition.
3. resulting polymers are normally linear.
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Their structural units usually have the same
composition as the monomer.
RING-OPENING
POLYMERIZATION
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(image 73)
1. type
2. what is the X?
RING-OPENING
POLYMERIZATION
X may be a **heteroatom** such as O, S,
or a group like NH, –O–CO–, –NH–CO, or –C›
C–.
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________________ is capable of ring-opening
polymerization to produce a linear chain of
**degree of polymerization, n.**
Cyclic structure
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such that it** provides a mechanism** for a
catalyst or initiator **to form the initiating
coordination intermediate** with the cyclic
ring.
nature of X
