Spring 2004 Basic Principles and Introduction Prof. Y.M. Lee School of Chemical Engineering, College of Engineering Hanyang University Polymer Chemistry.

Spring 2004

Basic Principles and Introduction

Prof. Y.M. Lee

School of Chemical Engineering, College of EngineeringHanyang University

Polymer Chemistry

Spring 2004

We live in a polymer age!!We live in a polymer age!!

PlasticsPlastics

FibersFibers

ElastomersElastomers

CoatingsCoatings

AdhesivesAdhesives

RubberRubber

ProteinProtein CelluloseCellulose

Spring 2004

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

Synthesis of Polymer: Synthesized from simple molecules called “monomers”

CH2 CH2 CH2 CH2 ** n Ethylene

CH2 CH CHCH2 ** n

Styrene

1) Addition Polymerization

Spring 2004

2) Condensation Polymerization

HOCH2CH2OH OCH2CH2* *n

-H2OEthylene glycol

4-Hydroxymethyl benzoic acid

HOCH2 CO2H

CH2 C

O

*O* n -H2O

Spring 2004

Historical Milestones in Polymer Science

• Prehistory – 19th CenturyMankind relies on natural polymeric materials like wood, bone, and fur.

• 1833Polymer was first used by the Swedish chemist Berzelius.

• 1839 Charles Goodyear vulcanizes natural rubber with sulfur, launches rubber industry. The polymerization of styrene was firstly reported.

•1860sPoly(ethylene glycol) and poly(ethylene succinate) was published.

*O

*n

*

O

O

*n

Spring 2004

•1870John Wesley Hyatt invents Celluloid through chemical treatment of natural cellulose (nitrated cellulose).

•1887Count Hilaire deChardonnet spins cellulose nitrate into Chardonnet silk

•1909American inventor Leo Baekeland (who had already earned considerable success with his light-sensitive photographic paper) treated phenol with formaldehyde to produce Bakelite, the first successful fully synthetic polymer material.

Historical Milestones in Polymer Science

Spring 2004

Historical Milestones in Polymer Science

•1920German chemist Hermann Staudinger proposes his Macromolecular Hypothesis, claims giant molecules exist (revealing view is that plastics are assemblies of small molecules). Staudinger is widely criticized but eventually becomes the first polymer chemist to win the Nobel Prize in Chemistry (in 1953).

•1928German chemists Kurt Meyer and Herman Mark confirm the existence of macromolecules through x-ray studies.

Spring 2004

Historical Milestones in Polymer Science

• 1928DuPont hires Professor Wallace Hume Carothers from Harvard to start first basic R&D lab in the USA.

•1930s - An explosion of new materials. Wallace Carothers - Polyamide (Nylon)

Polychloroprene (Neoprene)Waldo Semon - Polyvinyl chloride (PVC) Roy Plunket - Polytetrafluoroethylene (Teflon)Paul Flory - Theory of gelation

•1940sWWII leads to synthetic rubber programProfessor Peter Debye develops light scattering for MW meas

urementFlory and Huggins develop theory of polymer thermodynamics

Spring 2004

Historical Milestones in Polymer Science

• 1953German chemist Karl Ziegler and Italian chemist Giulio Natta develop effective catalysts for olefin polymerization allowing large scale production of polyethylene and polypropylene. They receive the Nobel Prize in 1963.

• 1974 Professor Paul Flory is awarded the Nobel Prize in Chemistry for his many contributions to polymer science.

• 1986Chemical Engineering Professor Robert Langer and Medical Doctor Joseph Vacanti demonstrate the use of polymers in tissue engineering. Liver cells grown on a special polymer can be transplanted and still function.

Spring 2004

Historical Milestones in Polymer Science

• 2000The Nobel Prize in Chemistry is given “for the discovery and development of electrically conductive polymers.”

Professor Alan J. Heeger at the University of California at Santa Barbara, USA

Professor Alan G. MacDiarmid at the University of Pennsylvania, USA

Professor Hideki Shirakawa at the University of Tsukuba, Japan

Polymer Science and Technology remains a vital and exciting field!

Spring 2004

Important 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 2004

Chap 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)

n

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).

- 2

Spring 2004

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 2004

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

(a) Star (b) Comb

(c) Ladder (d) Semiladder

Representation of polymer types

Spring 2004

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 2004

Traditionally, polymers have been classified into two main groups: 1) addition polymers and2) 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 2004

3. Polyurethane from diisocyanate and diol

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

Spring 2004

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 2004

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

N

NNp

)1( pNN o

pDP

N

No

1

1

or

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

Carothers’ equation

Spring 2004

2. 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 2004

3. Comparison of step-reaction and chain-reaction polymerization

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

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 2004

Vinyl polymersNomenclatures

Spring 2004

Nonvinyl polymers

Spring 2004

Nonvinyl polymers

Spring 2004

Plastics

Commodity plastics

Industiral polymers

Spring 2004

Engineering plastics

Spring 2004

Thermosetting plastics

Spring 2004

FibersSynthetic fibers

Spring 2004

Synthetic rubber

Rubber (elastomers)

Spring 2004

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 BondC O

O

Zn O C O+1 _

_

_

_

Van der Waals CH2

CH2

Spring 2004

PE

m

r

Attraction

Repulsion

Spring 2004

Chap 4. Stereoisomerism Activity (Tacticity)

Atactic C

CH3

C C C C C C C C

CCCCCCCCC

CCCCCCCCC

CH3

CH3

CH3

CH3

CH3

CH3 CH3

CH3

CH3

Isotactic

Syndiotactic

CH3 CH3

CH3

Spring 2004

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 2004

c =

massvolume

=4 14 AMU

93.3 Ao 3

gm

6.023 10 23 AMU cm3

1024 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 2004

결정화의 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 2004

Crystallizability

고분자의 화학구조에 의한 고유의 성질

구조의 규칙성 강한 친화력

Crystallinity

가공 history 에 직접 의존

Temperature/time Stress/time

Spring 2004

몇가지 결정 MODELS

1. Fringed-Micelle Model

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

orientation

Spring 2004

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 2004

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 2004

4. 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 2004

Spring 2004

V = Vc wc + Va (1 wc)

Vc : calculated x-ray(1 / c

wc : wt ftaction of xtalls

Specific volume