Hanyang Univ. Spring 2007 Basic Principles and Introduction Prof. Y.M. Lee School of Chemical...

Hanyang Univ.Hanyang Univ.

Spring 2007

Basic Principles and Introduction

Prof. Y.M. LeeSchool of Chemical Engineering, College of Engineering

Hanyang University


Spring 2007We live in a polymer age!!We live in a polymer age!!

Plastics

Fibers

Elastomers

Coatings

Adhesives

Rubber

Protein Cellulose

Polymers are everywhere !!!

Click the next homepage

http://www.pslc.ws/mactest/level1.htm

Surfing to the internet

http://www.pslc.ws/mactest/level1.htm


Spring 2007

"I just want to say one word to you -- just one word -- 'plastics.'"

Advice to Dustin Hoffman's character in The Graduate


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


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


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


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


Spring 2007

HDPE vs LDPE

HDPELDPE

The branching increases the volume and thus reduces the density of the polymer.


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


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


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-


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)


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


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.


Spring 2007

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.


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,

Click next homepage.

http://www.pslc.ws/mactest/tact.htm





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


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


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


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)


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!!

http://100.file.daum.net/spotlight/data/nobel/npw/winners.html


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)


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.


http://www.pslc.ws/quizzes/poly0.htm


Spring 2007

Chapter 2 .Classification of Polymer by polymerization reaction types

Addition Polymerization Condensation Polymerization Ring opening polymerization Step polymerization Chain polymerization


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)


Spring 2007

2) Condensation Polymerization

HOCH2CH2OH OCH2CH2* *n -H2O

Ethylene glycol

4-Hydroxymethyl benzoic acid

HOCH2 CO2H

CH2 C

O

*O* n -H2O


Spring 2007

2. Polyamide from lactam and ω-amino acid

1. Polyester from lactone and ω-hydroxycarboxylic acid:

Example


Spring 20073. Polyurethane from diisocyanate and diol

4. Hydrocarbon polymer from ethylene and ,ω-dibromide by the Wurtz reaction


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


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)


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


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.


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


Spring 2007

Progress of a Step-Growth Polymerization

Progress of a Chain-Growth Polymerization


Spring 2007Vinyl polymersNomenclatures


Spring 2007

Nonvinyl polymers


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.


http://www.pslc.ws/quizzes/assess/NAMING/NAMING.HTM


Spring 2007

PlasticsCommodity plastics

Industiral polymers


Spring 2007Engineering plastics


Spring 2007

Thermosetting plastics


Spring 2007

FibersSynthetic fibers


Spring 2007

Synthetic rubber

Rubber (elastomers)


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 _

_

_

_


Spring 2007

PE

m r

Attraction

Repulsion

Van der Waals CH2

CH2


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


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


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


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.


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


Spring 2007

Semicrystalline polymers1. Fringed-Micelle Model Fringed-Micelle(or crystallites) spread within the amorphous matrix

orientation


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.


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”


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.


Spring 2007

Hanyang Univ. Spring 2007 Basic Principles and Introduction Prof. Y.M. Lee School of Chemical...

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