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Polymer Chemistry
고분자화학
Course Overview
담당 교수: 윤영수
E-mail: [email protected]
[email protected]
Phone: 033-570-6540
Office: 3E320
TEXT BOOK:
“CONTEMPORARY POLYMER CHEMISTRY” 3rd edition
(Harry R. Allcock, Frederick W. Lampe, James E. Mark)
CONTEMPORARY
POLYMER
CHEMISTRY
Harry R. Allcock
Frederick W. Lampe
James E. Mark
Goal
This course is designed to provide an introduction to polymer
chemistry, including the synthesis, analysis, and physicochemical
properties of macromolecules. Additional lectures will be on examples of
polymer applications in industrial fields in order to understand polymers.
(본 강의는 고분자 화학에 대한 개론으로 합성법, 분석법 및 물리화학적 특
징들을 제공한다. 또한, 실제 응용 사례들을 접함으로써 고분자에 대한 전
반적인 이해를 하도록 한다.)
“Polymers are Everywhere”
1. DEFINITIONS
1.1 Monomers
A monomer is any substance that can be converted into a polymer.
Polymerization
Monomers
Small molecules
Polymer
One large molecule
(Ethylene)
(Amino acid)
(Polyethylene)
(Polypeptides)
1.2 Dimers and Trimers
Monomer + Monomer = Dimer
Dimer
+ Monomer = Trimer
…Tetramer, Pentamer, ,,,
1.3 Oligomers
Low-molecular weight polymerization products
-Dimers, trimers, tetramers, pentamers, and so on – cyclic or linear
Glycolic acid
(monomer)
Dimer
Trimer
Example of Oligomers
Benzene
(cyclic trimer)
Acetylene
(monomer)
Polyacetylene
Trioxane
(cyclic trimer)
Formaldehyde
(monomer)
Polyformaldehyde
1.3 Polymers
- The term polymer is used to describe high-molecular-weight substances.
Polymer: large molecules made up of simple repeating units
Greek poly, meaning many, and mer, meaning unit
Synonymous Term: Macromolecules
- However, this is a very broad definition, and in practice it is convenient to
divide polymers into subcategories according to their molecular weight and
structure.
- Generally, low polymers = MW 10,000 ~ 20,000
High polymers = MW 20,000 ~ several million
2. CLASSIFICATION OF POLYMERS
Representation of polymer types
2.1 Linear Polymers
- A long chain of skeletal atoms to which are attached the substituent groups.
- Linear polymers are usually soluble in some solvent, and in the solid state at
normal temperatures they exist as flexible materials, or glasslike thermoplastics.
EX) Polyethylene, Poly(vinyl chloride, PVC), Poly(methyl methacrylate, PMMA),
Polyacrylonitrile, Nylon
2.2 Branched Polymers
- Consisting of side chains or branches in the main chain
- They are often soluble in the same solvents as the corresponding linear
polymer
-However, they can sometimes be distinguished from linear polymers by their
lower tendency to crystallize or by their different solution viscosity or light
scattering
2.3 Crosslinked Polymers
- This polymer is one in which chemical linkages exist between the chains.
Such materials are usually swelled by “solvents” but do not dissolve.
- Actually, the amount by which the polymer is swelled by a liquid depends on
the density of crosslinking.
- Degree of crosslinking is high enough, the material may be a rigid, highmelting, unswellable solid.
crosslinking
crosslinking
2.4 Star Polymers
- Star polymers have arms radiating from a common core.
- The number of arms may from three to six or more.
- Such polymers are prepared either by growing the arms by polymerization
from a multifunctional core, or by linking preformed polymer molecules to a
core through reactive end groups on the polymer.
Tri-star polymer
2.5 Dendrimeric Polymers
Preparation method
1. Core-first: they are accessible through the reactions of a multifunctional
core with a ti- (or higher) functional monomer. The growth of the molecule
is usually carried out in successive layers or “generations” moving further
and further from the core.
2.
Arms-first: each highly branched arm is synthesized first, and several of
these are then linked in a final step to the core.
1st generation
2nd generation
3rd generation
2.6 Cyclolinear Polymers
- A special type of linear polymer formed by the linking together of ring systems.
-The properties resemble those of conventional linear polymers, except that
the solubility of the cyclolinear species is often low.
-The tendency for crystallization may be very high.
2.6 Ladder Polymers
-Two skeletal strands are linked together in a regular sequence by
crosslinking units. In practice, aromatic rings may constitute the linking units.
-Ladder polymers have a more rigid molecular structure than do conventional
linear polymers and they are often much less soluble.
R: polymer chain
2.7 Cyclomatrix Polymers
- Many polymer systems are known in which ring system are linked together
to form a three-dimensional matrix of connecting units.
- Since 3D network of bonds is formed in these systems, the polymers are
highly insoluble, rigid, very high melting, and usually stable at elevated
temperatures.
Silicon resins
2.8 Copolymers
- A polymer is made from two or more different monomers.
- It should be noted that the sequence of monomer units along a copolymer
chain can vary according to the method and mechanism of synthesis.
2.8.1 Random copolymers
- In random copolymers, no definite sequence of monomer units exists.
Poly (A-ran-B)
A–B–A–A–A–B–A–B–B–A–A–B–A
2.8.2 Alternating copolymers
- A regular alternating sequence of two monomer units
Poly (A-alt-B)
A–B–A–B–A–B–A–B–A–B–A–B
2.8.3 Block copolymers
- Combination of one block of monomers and another block of monomers
- They are often formed by ionic polymerization process.
Ex) AB diblock copolymers
A–A–A–A–A–B–B–B–B–B
Ex) ABA triblock copolymers
A–A–A–A–B–B–B–B-A–A–A–A
2.8.4 Terpolymer
- A terpolymer contains three different monomer units. These can be
sequenced randomly or in blocks.
2.8.5 Graft Copolymers
Two preparation methods
1) Monomer B can be polymerized from sites along the length of polymer A.
–B–B
–B–B–B–B
– B–B
–B–B–B–B
2) Two preformed polymers derived from A and B can be induced to react
with each other to form a graft structure.
A–A–A–A–A–A–A–A–A–A–A–A
2.8.6 Telechelic Polymers
- A telechelic polymers is one that bears reactive functional groups at one or
both of its chain ends.
- These are frequently produced by living polymerization processes.
2.9 Average Molecular Weights and Distributions
- A sample of a synthetic polymer has no single, fixed molecular weight.
- Instead, there is a distribution of different molecular weights in the same
sample of material.
1) Number-average molecular weight
Ni: Number of molecules of molecular weight Mi
Xi: Number fraction or mole fraction of molecular weight Mi
*It can be obtained from the study of the osmotic pressure of polymer solutions.
2) Weight-average molecular weight
vi: Weight of molecules of molecular weight Mi
Wi: Weight fraction of molecules with molecular weight Mi
*It can be obtained from light-scattering or ultracentrifugation experiments, GPC
3) Polydispersity index (PDI, fraction MW/Mn)
The fraction is a measure of the molecular weight distribution.
For most polymers Mw/Mn: 1.5 – 2.5
For monodisperse polymer: Mw/Mn = Mz/Mw = 1
Mw
> 1 Polydisperse
Mn
Mw
Mn
= 1 Monodisperse
2.10 Polymer Morphology
2.10.1 Thermoplastics
- Linear or branched polymers which can be melted upon the application of
heat. (Largest proportion of the polymers used in industry.)
2.10.2 Elastomers
- A flexible polymer that is in the temperature range between its glass
transition temperature and its liquefaction temperature.
- Crosslinked rubbery polymers that can be stretched easily to high
extensions and which rapidly recover their original dimensions when the
applied stress is released.
- Low crosslink density
2.10.3 Plasticizers
- Only when this rigid polymer is softened by the addition of low-volatility
liquids, such as phthalate esters, can it be used as flexible-film or tygon
tubing.
2.10.4 Thermosetting Resin
- Rigid materials and network polymers in which chain motion is greatly
restricted by a high degree of crosslinking.
2.10.5 Polymer blends
- Two or more polymers are mixed together mechanically.
- Many polymer blends display properties that are different from those of the
individual polymers.
- Polymer blends can be of two main types, miscible or immiscible.
Comparison of the thermal behavior of amorphous,
crystalline, and liquid crystalline polymers
Summary
Definition of Polymer
- High molecular weight polymers
- Average molecular weight and distribution
Classification of Polymers
- Linear, branched, crosslinked, dendrimeric, star, ladder
polymers
- Copolymers: random, alternating, block copolymers
- Grafting polymers and Telechelic Polymers
Polymer morphology
- Thermosetting resin, Elastomers, Thermoplastics, Polymer blends