Polymer Chemistry Basic Principles and Introduction Prof. Y.M. Lee

Hanyang Univ.Hanyang Univ.

Spring 2006

Basic Principles and Introduction

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

Hanyang University

Polymer Chemistry


Spring 2006We 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 2006

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

Advice to Dustin Hoffman's character in The Graduate


Spring 2006

Polymer: large molecules made up of simple repeating units Greek poly, meaning many, and mer, meaning part Synonymous Term: Macromolecules


Spring 2006Synthesis of Polymer:

Synthesized from simple molecules called “monomers”

CH2 CH2 CH2 CH2 ** n Ethylene

CH2 CH CHCH2 ** n

Styrene

1) Addition Polymerization


Spring 20062) Condensation Polymerization

HOCH2CH2OH OCH2CH2* *n -H2O

Ethylene glycol

4-Hydroxymethyl benzoic acid

HOCH2 CO2H

CH2 C

O

*O* n -H2O


Spring 2006Historic 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 2006

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 2006• 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 2006

• 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


Spring 2006Important 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 2006Quiz

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 2006Chap 2. Types of Polymers & Definitions

Polymer: a large molecule whose structures depends on the monomer or monomers used in preparationOligomer: low-molecular weight polymer (a few monomer units)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

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).

n


Spring 2006

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-

Definitions


Spring 2006

(a) Linear (b) Branched (c) Network

(a) Star (b) Comb

(c) Ladder (d) Semiladder

Representation of polymer types


Spring 2006

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 2006

Traditionally, polymers have been classified into two main groups: 1) addition polymers and 2) condensation polymers (first proposed by Carothers)

1. Polyester from lactone and ω-hydroxycarboxylic acid:

2. Polyamide from lactam and ω-amino acid

Polymerization processes (traditional)


Spring 20063. Polyurethane from diisocyanate and diol

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


Spring 2006

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) orby 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 2006

If one assumes that there are No molecules initially and N molecules (total) after a givenreaction period, then amount reacted is No-N. The reaction conversion, p, is then given bythe expression

o

o

NNNp

)1( pNN o

pDP

NNo

11

or

Ex) At 98% conversion, p = 0.98 DP = 50

Carothers’ equation


Spring 20062. 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 2006

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 2006

Polymerization mechanisms

- Step-growth polymerization


Spring 2006

Polymerization mechanisms

- Chain-growth polymerization


Spring 2006Vinyl polymersNomenclatures


Spring 2006

Nonvinyl polymers


Spring 2006

Nonvinyl polymers


Spring 2006Quiz 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.






Spring 2006

PlasticsCommodity plastics

Industiral polymers


Spring 2006Engineering plastics


Spring 2006

Thermosetting plastics


Spring 2006

FibersSynthetic fibers


Spring 2006

Synthetic rubber

Rubber (elastomers)


Spring 2006

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 2006

PE

m r

Attraction

Repulsion

Van der Waals CH2

CH2


Spring 2006Chap 4. Stereoisomerism Activity (Tacticity)

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






Spring 2006

How to Determine Tacticity?13C NMR is a very powerful way to determine the microstructure of a polymer.

13C NMR shift is sensitive to the two stereocenters on either side on sptectrometers > 300 MHz. This is called pentad resolution.

r mm rmr

mmrm pentadm = meso (same orientation)r = racemic (opposite orientation)

12 1 2


Spring 2006

Unit cell

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. 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 5. Crystallinity


Spring 2006

c =mass

volume =4 14 AMU

93.3 Ao 3

gm

6.023 10 23 AMU cm31024 3o

A

= 0.997 gm / 3cmCrystal density

CH2

H2C

CH2

H2C

H2C

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2

CH2 CH2

CH2 CH2

CH2

Polyethylene: a = 7.41Å , b = 4.94Å , c = 2.54Å ( Chain axes )

Unit cell volume = a×b×c = 93.3 Å3

Mass in cell corner = 8 CH2’s shared / 8 cells = 1 CH2

2 sidewall CH2’s = 2/2 = 1 CH2

Top & bottom face CH2’s =


Spring 2006결정화의 조건

1. 정규 결정 격자로 사슬이 packing 되려면 ordered, regular chain structure 가 필요 . 따라서 stereoregular structure 를 가진 고분자가 irregular structure 를 가진 고분자보다 결정화가 될 확률이 높다 .

2.결정격자간 2 차 간력이 강해서 열에너지에 의한 무질서 효과 ( 엔트로피 효과 ) 를 극복할 수 있어야 함 .

biaxial stress(stretching) is stronger than uniaxial stretch ∵different arrangement of chain.


Spring 2006Crystallizability

고분자의 화학구조에 의한 고유의 성질

구조의 규칙성 강한 친화력

Crystallinity

가공 history 에 직접 의존

Temperature/time Stress/time

For further details,

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http://www.pslc.ws/macrogcss/crystal.html






Spring 2006몇가지 결정 MODELS

1. Fringed-Micelle Model

fringed-micelle(or crystallites) 가 amorphous matrix 내에 퍼져 있음

orientation


Spring 2006

2. Folded-Chain Crystallites

희박용액으로부터 single crystal 이 성장하여 polymer crystal 이 생성됨을 발견 . 냉각 또는 solvent 가 evaporation 함으로서 thin, pyramidal, or platelike polymer crystal(lamellae) 가 생성 . 이 결정들은 두께 약 100Å 에 수십만 Å 길이를 가짐 . X-ray 결과로는 chain axis 가 flat surface 에 수직으로 배열 됨이 알려짐 . 또한 각자 사슬들이 1000Å 이상의 길이를 가짐 . 따라서 chain 이 folded back and forth 할 수 밖에 없다는 결론 . Dilute solution 으로부터 뿐 아니라 melt 로부터도 이 같은 lamellae 형성 model 이 적용됨 .


Spring 2006

3. Extended-Chain X-tal

melt 상태에서 extension(stress) 을 가하면서 결정화가 일어날 때 확장하는 방향으로 사슬이 배열하며 fibrillar 구조를 형성 . 이들은 extended-chain crystals 로 알려져 있고 이들은 먼저 서로 평행으로 배열되어 있고 chain folding 은 minimum.

“Shish-Kebab”


Spring 20064. Spherulites

고분자 사슬들은 crystallites 를 형성할 수 있도록 배열되어 있으며 이들 crystallites들은 spherulites 라고 하는 커다란 집합체로 되어 있다 . 이들 spherulites 는 핵형성점 으로부터 원형으로 성장 . 따라서 각개 spherulites 는 존재하는 핵의 숫자로부터 조절될 수 있으며 핵이 더 있으면 더 많은 작은 spherulites 가 됨 . Spherulites 가 큰 것들은 고분자의 brittleness . Brittleness 를 적게 하려면 nucleating agent 를 첨가하든가 고분자를 shock cooling 함 .


Spring 2006


Spring 2006

V = Vc wc + Va (1 wc)

Vc : calculated x-ray(1 / c

wc : wt ftaction of xtalls

Specific volume

For further details, Click next homepage.

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

&

http://plc.cwru.edu/tutorial/enhanced/files/polymers/orient/orient.htm




http://plc.cwru.edu/tutorial/enhanced/files/polymers/orient/orient.htm


Spring 2006Polymer Conformation

Virtual Experiment

Case Western Reserve Univ.Polymer and Liquid Crystals

Conformation Lattice SimulationClick the next homepage, experiment part

http://plc.cwru.edu/tutorial/enhanced/lab/lattice/lattice.htm

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Polymer Chemistry Basic Principles and Introduction Prof. Y.M. Lee