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Spring 2007
Basic Principles and Introduction
Prof. Y.M. LeeSchool of Chemical Engineering, College of Engineering
Hanyang University
Hanyang Univ.Hanyang Univ.
Spring 2007We live in a polymer age!!We live in a polymer age!!
Plastics
Fibers
Elastomers
Coatings
Adhesives
Rubber
Protein Cellulose
Polymers are everywhere !!!
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Spring 2007
"I just want to say one word to you -- just one word -- 'plastics.'"
Advice to Dustin Hoffman's character in The Graduate
Hanyang Univ.Hanyang Univ.
Spring 2007
Monomer, Dimer, Trimer…., OligomerA monomer (from Greek mono "one" and meros "part") is a small molecule that may become chemically bonded to other monomers to form a polymer.
CH2 CH2 ** n
CH2 CH2Ethylene Polyethylene
monomer Polymer
The lower molecular weight compounds built from monomers are also referred to as dimers, trimers, tetramers, quadramers, pentamers, octamers, 20-mers, etc. Polymers with relatively low number of units are called oligomers
HO CH2CO
OH HO CH2CO
O CH2C OHO
2monomer dimer
HO CH2CO
O CH2C OO
TrimerCH2C OH
O
Chapter 1 .The Scope of Polymer Chemistry
Hanyang Univ.Hanyang Univ.
Spring 2007
Polymer: large molecules made up of simple repeating units Greek poly, meaning many, and mer, meaning part Synonymous Term: Macromolecules
Repeating unit (RU): monomeric units (examples: polyethylene) Degree of polymerization (DP): the total number of structural units, including end groups. It is related to both chain length and molecular weight
Hanyang Univ.Hanyang Univ.
Spring 2007
CH C
O
C O
CH3
** n
-2CH2 CH
O
C O
CH3
Vinyl acetate (a important industrial
monomer)
If DP (n) = 500, for example, M.W.= 500 × 86(m.w. of structural unit) = 43,000Because polymer chains within a given polymer sample are almost always of varying lengths(except for certain natural polymers like proteins), we normally refer to the average degree of Polymerization (DP).
nEx.
Low polymer: molecular weight < 10,000 to 20,000 repeating units < 1000 to 2000 High polymer: molecular weight > 10,000 to 20,000 repeating units > 1000 to 2000
1000-2000
Pro
pert
y
Number of repeating unit
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Spring 2007
Types of polymer a) Linear
PolymersLinear polymer consists of a long chain of skeletal atoms to which are attached the substituent groupsEx) PVC, PMMA, PE , Nylon
b) Branch Polymerslinear polymers with branches in which chemical linkages exist
between the chains
c) Cross linked Polymers
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Spring 2007
HDPE vs LDPE
HDPELDPE
The branching increases the volume and thus reduces the density of the polymer.
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Spring 2007
Types of polymer d) Star Polymers have arms (3 or more) radiating from a common core
e) Dendritic Polymers (Dendrimer)
f) Ladder Polymersconsists of linesr molecules in
which two skeletal strands are linked together in a regular sequence by crosslinking units
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Spring 2007
i) Interpenetrating network (IPN)
g) Cyclolinear Polymers linking together of ring systems
h) Cyclometrix Polymers Ring systems are linked together to
form a three dimensional matrix of connecting units
HC CH2 HC CH2
CH CH2
AIBN
styrene
divinylbenzenePEA-PS IPN
PEA network
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Spring 2007
Copolymer
Homopolymer: -A-A-A-A-A-A-A-A-A-
Copolymer:(1) Alternating copolymer: -A-B-A-B-A-B-A-B-A-B-A-B-(2) Random copolymer: -A-A-B-A-B-B-A-B-(3) Block copolymer: -A-A-A-A-A-A-B-B-B-B-B-B-(4) Graft copolymer: -A-A-A-A-A-A-A-A-A-A-A-A-
BB-B-B-B-B-B-B-
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Spring 2007
Network polymers arise when polymer chains are linked together or when polyfunctional instead of difunctional monomers are used.Ex) Vulcanized rubber
PolymerChains
crosslink1. Excellent dimensional stability2. X-polymers will not melt or flow and cannot be molded.
(thermosetting or thermoset thermoplastic)3. Usually insoluble, only swelling
Network Polymers (Crosslinked polymers)
Hanyang Univ.Hanyang Univ.
Spring 2007Thermoplastic & Thermosetting Polymer
Thermoplasic Thermosettingthermoplastic polymers are defined as materials that soften, melt, and flow when heat is applied; the adhesives solidify when cooled. Majority of familiar plasticsCan be reprocessedPolyethylene (LDPE / MDPE /HDPE),Polyamide, PEK, TPU, PET, PVC
A thermosetting polymer, as the name suggests, becomes set into a given network, normally through the action of a catalyst—heat, radiation, or a combination of these factors—during the process of cross-linking. As a result of this process, thermosets become infusible and insoluble. Hard, strong, rigidExcellent heat resistanceCannot be reprocessedCrystallineEpoxy, phenolic, polyester,Rubber, silicone, polyurethane
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Spring 2007
Molecular conformation & configuration1) Molecular conformation
Molecular conformation refers to the spatial arrangement of substituent groups that, without breaking any bonds, are free to assume different positions in space because of the freedom of bond rotation.
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2) Molecular configurationConfiguration denotes the fixed spatial arrangement of atoms in a molecule that is conferred by the presence of either:
(1) double bonds, around which there is no freedom of rotation
(2) chiral centers, around which substituents are arranged in a specific sequence.
Configurational isomers cannot be interconverted without temporarily breaking one or more covalent bonds.
An example of configurational isomers…
Geometric or cis/trans isomers: they cannot be interconverted without breaking bonds.
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Spring 2007
Tacticity- Isotatic, Syndiotactic, Atactic (heterotactic)
Atactic
C
CH3
C C C C C C C C
CCCCCCCCC
CCCCCCCCC
CH3
CH3
CH3
CH3
CH3
CH3 CH3CH3
Isotactic
Syndiotactic
CH3 CH3
For further details,
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Spring 2007
Why is this important? (Tacticity) Tacticity affects the physical properties
– Atactic polymers will generally be amorphous, soft, flexible materials
– Isotactic and syndiotactic polymers will be more crystalline, thus harder and less flexible
Polypropylene (PP) is a good example– Atactic PP is a low melting, gooey material– Isoatactic PP is high melting (176º), crystalline, tough material
that is industrially useful– Syndiotactic PP has similar properties, but is harder to
synthesize
Hanyang Univ.Hanyang Univ.
Spring 2007Historic Highlights in Polymer Chemistry
• 1600 BC - Meso-americans produce Rubber• rubber balls• rubber handles for tools (600-900 AD)• medicinal chewing gum, rubber boots and clothes (1400 AD)
• 1830 AD - Re-invention of Rubber. New -vulcanisation with Sulphur - Charles Goodyear
• pneumatic tire (Real: 1845 Thomson, but ‘copy’1888 Dunlop)
• 1846 Gun Cotton by Christian Schönberg• 1866 - Celluloid Wesley Hyatt & Alexander Parkes
• billiard balls
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Spring 2007
Meso-American Rubber
• Latex from Castilla Elastica• Liquid extracted from Ipomoea Alba (morning glory vine)
Mixing causes:Latex coagulation and purificationIntroduction of plasticizers
Thermal curing:Crystalline entanglementsChemical crosslinking via sulfonyl chlorides and acids
* *n
Hanyang Univ.Hanyang Univ.
Spring 2007• 1907 - Bakelite Leo Baekeland
• electrical insulator• light-weight war machinery
• 1924 Concept of Macromolecules H.Staudinger (Nobel Prize 1953)
• 1929 Concepts of Addition and Condensation polymers, Wallace H. Carothers
• neoprene• polyesters• nylons
• 1929 Plastisizing PVC by Waldo Semon• 1938 TEFLON by Roy Plunkett• 1943/1949 Silly Putty by James Wright/Peter Hodgson• 1953/1954 Polyethylene/polypropylene Karl Ziegler &
Giulio Natta (Nobel Prize 1963)
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Spring 2007
• 1974 Paul J. Flory Nobel Prize• Flory temperature• Chain Transfer• Universal constant
• 1991 Pierre-Gilles de Gennes Nobel Prize• Reptation model
• 2000 Heeger, Macdiarmid, Shirakawa Nobel Prize • conductive polymers
• 2002 - John B. Fenn, Koichi Tanaka, Kurt Wüthrich Nobel Prize
• Structural determination biomacromolecules
• Historical winner of the Nobel Prize List – Click!!
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Spring 2007Important Advances in Polymer Science
• High thermal and oxidation-stable polymer: high performance aerospace applications • Engineering plastics – polymers designed to replace metals • High strength aromatic fibers – a variety of applications from tire cord to cables for anchoring oceanic oil-drilling platforms • Non flammable polymers – emit a minimum of smoke or toxic fumes • Degradable polymers – allow controlled release of drugs or agricultural chemicals • Polymer for a broad spectrum of medical applications – from degradable sutures to artificial organs • Conducting polymers – exhibit electrical conductivities comparable to those of metals • Polymer that serve as insoluble support for catalysts or for automated protein or nucleic acid synthesis (Bruce Merrifield, who originated solid-phase protein synthesis, was awarded the Nobel Prize in Chemistry in 1984)
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Spring 2007Quiz
University of Southern MississippiPolymer Science Learning Center
---------------------------------------------------------------General Polymer Knowledge TestClick the next homepage
http://www.pslc.ws/quizzes/poly0.htm
If you take quizzes more than once, you will get different questions, so try them again.
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Spring 2007
Chapter 2 .Classification of Polymer by polymerization reaction types
Addition Polymerization Condensation Polymerization Ring opening polymerization Step polymerization Chain polymerization
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Spring 2007
1) Addition Polymerization
Styrene CH2 CH * CH2 CH *
Methyl Methacrylate CH2 CCH3
CO2CH3 * CH2CCH3
CO2CH3
*
Polymerization processes (traditional)Traditionally, polymers have been classified into two main groups: 1) addition polymers and 2) condensation polymers (first proposed by Carothers)
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Spring 2007
2) Condensation Polymerization
HOCH2CH2OH OCH2CH2* *n -H2O
Ethylene glycol
4-Hydroxymethyl benzoic acid
HOCH2 CO2H
CH2 C
O
*O* n -H2O
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Spring 2007
2. Polyamide from lactam and ω-amino acid
1. Polyester from lactone and ω-hydroxycarboxylic acid:
Example
Hanyang Univ.Hanyang Univ.
Spring 20073. Polyurethane from diisocyanate and diol
4. Hydrocarbon polymer from ethylene and ,ω-dibromide by the Wurtz reaction
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Spring 2007
3) Ring opening polymerizationO
H2C
OCH2
O
CH2
n catalyst* CH2 O *n
(CH2)5 C
NH
O * NH (CH2)5 C *
O
n
O
H2C CHR * O CH2 CH *
R
nTertiary amines
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Spring 2007
In more recent years the emphasis has changed to classifying polymers according to whether the polymerization occurs in a stepwise fashion (step reaction or step growth) or by propagating from a growing chain (chain reaction or chain growth).
1. Step reaction polymerization
A B A B* *n
A A B B * A A B B *n +
Reactive functional group in one molecule
Two difunctional monomers
Ex) Polyesterification diol + dibasic acid or intermolecularly between hydroxy acid molecules
Polymerization processes (recent)
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Spring 2007
If one assumes that there are No molecules initially and N molecules (total) after a given reaction period, then amount reacted is No-N. The reaction conversion, p is then given by the expression
o
o
NNNp
)1( pNN o
pDP
NNo
11
or
Ex) At 98% conversion, p = 0.98 DP = 50
Carothers’ equation
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Spring 20072. Chain-reaction polymerization
Chain-reaction polymerization involves two distinct kinetic steps, initiation and propagation.
Initiation
Propagation
R CH2 CH2+ RCH2CH2..
RCH2CH2. CH2 CH2+ RCH2CH2CH2CH2
.
In both addition and ring-opening polymerization, the reaction propagates at a reactivechain end and continues until a termination reaction renders the chain end inactive (e.g., combination of radicals), or until monomer is completely consumed.
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Spring 2007
Step reaction
Growth occurs throughout matrix by reactionbetween monomers, oligomers, and polymers
DP low to moderate
Monomer consumed rapidly while molecularweight increases slowly
No initiator needed; same reaction mechanismthroughout
No termination step; end groups still reactive
Polymerization rate decreases steadily asfunctional groups consumed
3. Comparison of step-reaction and chain-reaction polymerization
Chain reaction
Growth occurs by successive addition of monomerunits to limited number of growing chains
DP can be very high
Monomer consumed relatively slowly, but molecularweight increases rapidly
Initiation and propagation mechanisms different
Usually chain-terminating step involved
Polymerization rate increases initially as initiator unitsgenerated; remains relatively constant until monomerdepleted
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Spring 2007
Progress of a Step-Growth Polymerization
Progress of a Chain-Growth Polymerization
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Spring 2007Vinyl polymersNomenclatures
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Spring 2007
Nonvinyl polymers
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Spring 2007
Nonvinyl polymers
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Spring 2007Quiz 2
University of Southern MississippiPolymer Science Learning Center
---------------------------------------------------------------Naming of polymers: What works and doesn’tClick the next homepage
http://www.pslc.ws/quizzes/assess/NAMING/NAMING.HTM
If you take quizzes more than once, you will get different questions, so try them again.
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Spring 2007
PlasticsCommodity plastics
Industiral polymers
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Spring 2007Engineering plastics
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Spring 2007
Thermosetting plastics
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Spring 2007
FibersSynthetic fibers
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Spring 2007
Synthetic rubber
Rubber (elastomers)
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Spring 2007
Chap 3. Bonding in Polymers
Primary Covalent Bond C C C H
Hydrogen Bond OH
H OC O H N
+
+
Dipole Interaction C N
N C
+
Ionic Bond C O
O
Zn O C O+1 _
_
_
_
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Spring 2007
PE
m r
Attraction
Repulsion
Van der Waals CH2
CH2
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Spring 2007
Six crystal system Isometric ; 3 mutually perpendicular axes of equal length. Tetragonal ; 3 perpendicular axes are equal in length. Orthogonal ; 3 perpendicular all of different length. Monoclinic ; 3 axes of unequal length.
Unit cell
2 are not to each other both are to the third Triclinic; all 3 axes of different length.
Hexagonal; 4 axes, 3axes in the same plane & symmetrically spa and of equal length.
Chap 4. Crystallinity
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Spring 2007
Polymer crystallinity
Some are amorphous, some are partially crystalline (semi-crystalline).-Why is it difficult to have a 100% crystalline polymer?
%100)()(%
acs
ascitycrystallin
rs = density of specimen in questionra = density of totally amorphous polymerrc = density of totally crystalline polymer
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Spring 2007
%100%100%100% cs
c
ss
cc
total
ecrystallin fVV
MM
itycrystallin
s
aa
s
ccs
aaccss
acs
amophousecrystallintotal
VV
VV
VVVMMM
MMM
s
cc VVf
What is fc? Volume fraction of crystalline component.
To get fc :
Using definition of volume fractions: ands
aa VVf
ac
asc
aaccs
caccaaccs
f
fffff
)()1(
Substituting in fc into the original definition: %100%
ac
as
s
citycrystallin
Polymer crystallinity
Hanyang Univ.Hanyang Univ.
Spring 2007Conditions for crystallization
1. Packing is facilitated for polymer chains that have structural regularity and compactness. In addition, polymers having stereoregular structure have higher degree of crystallinity comparing to polymers having irregular structure.
2. In the crystal lattice, the strong secondary attaractive forces affect the thermodynamic and kinetic freatures of the polymer.
biaxial stress(stretching) is stronger than uniaxial stretch ∵different arrangement of chain.
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Spring 2007
Conditions for crystallization
Degree of crystallinity depends on processing conditions (e.g. cooling rate) and chain configuration.
Cooling rate: during crystallization upon cooling through MP, polymers become highly viscous. Requires sufficient time for random & entangled chains to become ordered in viscous liquid.
Chemical groups and chain configuration:
More Crystalline
Smaller/simper side groups
Linear
Isotactic or syndiotactic
Less Crystalline
Larger/complex side groups
Highly branched
Crosslinked, network
Random
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Spring 2007
Semicrystalline polymers1. Fringed-Micelle Model Fringed-Micelle(or crystallites) spread within the amorphous matrix
orientation
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Spring 2007
2. Folded-Chain Crystallites There is a formation of polymer crystal as the single crystal grows from the dilute solution. Also from cooling or solvent evaporation process there is the formation of thin, pyramidal, or platelike polymer crystal(lamellae). The thickness of these crystallites is about 100Å where the length is several tens of thousands Å.From X-ray result, the chain axis is arranged in perpendicular way on the flat surface.Furthermore, each chain contains the lengh more than 1000Å. Therefore, it is concluded that the chain can only be folded back and forth. It can be seen not only from dilute solution but also from molten state where same lamellae type model is formed.
The chain-foided structure for a plate-shaped Polymer Crystallite.
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Spring 2007
3. Extended-Chain X-tal
In molten state, fibrillar structure is formed as the extension (stress) increases and the degree of crystallinity begin to rise where the chain arrangement takes place in the direction of expansion. They are known as extended-chain crystals and arranged in parallel way where the chain folding is minium.
“Shish-Kebab”
Hanyang Univ.Hanyang Univ.
Spring 20074. Spherulites
Polymer chains are arranged to form crystallites, a huge aggregate called as spherulites. These spherulites grow from nucleation to rounded circular shape. There is a control in the number of nucleus existing in each spherulites, therefore, more nucleus means more smaller spherulites. The bigger spherulites are one of the causes for the brittleness of polymer. So, adding nucleating agent to polymer or shock cooling process is performed to reduce the brittleness.
Hanyang Univ.Hanyang Univ.
Spring 2007
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