Polymer Chemistry

MBM 471

Lecture 1: Introduction

Faculty Asst. Prof. İlke Anaç (e-mail:ilkeanac@gyte.edu.tr)

Room: 212

Content-1

Introduction: Basic concepts and definitions, classification of

polymers, nomeculature of polymers, molecular weight and its

distribution

Polymerization mechanisms: Chain polymerization

-Free radical polymerization

-Cationic polymerization

- Anionic polymerization

Step- growth polymerization, ring-opening polymerization,

coordination polymerization

Chemical bonding and polymer structure, polymer molecular weight

Thermal transitions in polymers

Polymer modification: Copolymerization, post polymerization

reactions and functional polymers

Content-2

Assesment

Midterm- %35 (18 November)

Final: %50

Quiz- %10 (4 quiz)

Attendence % 5

Polymer additives and reinforcements

Polymerization techniques

Polymer processing: an overview of processing

techniques for thermoplastics and thermosets

Solution properties of polymers

Mechanical properties of polymers

Polymer viscoelasticity

Textbook

• Textbook: Polymer Science and Technology, Robert O Ebewele

(CRC press, New York,2000)

•

Additional Books: Introduction to Polymers, R.J. Young and P. A.

Lowell (Stanley Thornes, 2nd edition)

• Polymer Science & Technology, Joel R. Fried, Prentice Hall, 2nd

edition

• Polymer Kimyası, Prof. Dr. Mehmet Saçak, Gazi Yayınevi, 5. baskı

• Polymer Teknolojisi, Prof. Dr. Mehmet Saçak, Gazi Yayınevi, 5.

baskı

Historical Background

Ages ago - Natural Fibers Ex. Wool, silk, cotton

In 1736, Charles Marie de La

Condamine introduced the para

rubber tree (natural rubber).

Hevea brasiliensis

“Crying tree”

(para rubber) Latex Coating Natural (hevea) rubber known as

polyisoprene in its synthetic form.

1839-Charles Goodyear

Vulcanization: Transformation of sticky natural rubber to a useful

elastomer for tire use

Historical Background

S8

1843-Charles Goodyear Ebonite High % vulcanization (1st synthetic plastic made from natural rubber)

Fountain pen bodies smoking pipe mouthpiece bowling balls

Synthetic Polymers Started

cellulose cellulose nitrate

1847 “Cellulose nitrate”

1860s -Parkes (Electrical industry) and Hyatt (Billiard balls)

“Celluloid” (1st artificial thermoplastic)

Cellulose nitrate+ Camphor (as plasticizer)

1907-Leo Baekeland “Bakelite”

(thermosetting phenol-formaldehyde resin)

Bakelite letter opener

Bakelite distributor rotor

Bakelite radio

Bakelite telephone 1st truly synthetic plastic

On further heating with HCHO, novalac undergoes cross-linking to an infusible solid called bakelite. It is hard scratch and water resistant.

A chain of paper clips (above) is a good

model for a polymer such as polylactic acid (below).

Nobel Prize-Chemistry 1953 for “his discoveries in the field of macromolecular chemistry”

Hermann Staudinger

1920 “Macromolecular Hypothesis”

Demonstrations of both synthetic and natural polymers

Polymer is a giant molecule

long chains of short repeating

molecular units linked by covalent bonds

Between 1925-1950 Phenomenal growth in the number of polymeric products that achieved commercial use

1950`s acetal and polycarbonates (automotive and appliance parts)

1960s-1970s- thermoplastic polyesters (exterior automotive parts, bottles), high barrier nitrile resins and

high temperature plastics including materials such as polyphenylene sulfide, polyether sulfone.

Polymer –is a large molecule consisting of a number of repeating

units with molecular weight typically several thousand or higher

Polymers are made up of many Monomers

Many units One units

Repeating unit – is the fundamental recurring unit of a polymer

Monomer - is the smaller molecule(s) that are used to prepare a

polymer

Oligomer –is a molecule consisting of reaction of several repeat

units of a monomer but not large enough to be consider a polymer

(dimer , trimer, tetramer, . . .)

Degree of polymerization (DP)- number of repeating units

Polymer science is relatively a new branch of science . It deals with chemistry

physics and mechanical properties of macromolecule .

Definitions

3

2 1

Nylon 6,6

Zig-zag conformation

POLYETHYLENE

Substituent groups such as –CH3, -OCOCH3, CN, Cl or –Ph that are attached

to the main chain of the skeletal atoms are known as pendant groups. Their

structure and chemical nature can offer unique properties on polymer.

Classification of Polymers

A. Classification by Origin

• Natural Polymers

-Biological Origin - enzymes, nucleic acids, proteins

-Plant Origin – cellulose, starch, natural rubber

•Synthetic Polymers

- Fibers

- Elastomers

- Plastics

-Adhesives

3.Classification by Polymerization Mechanism

Classification of polymers to be suggested by Carothers

Addition polymers are produced by reactions in which monomers are added

one after another to a rapidly growing chain. Most important addition polymers

are polymerized from ethylene based polymers.

Trioxane

Ring opening polymerization

Polyoxymethylene

•Initiation

•Propagation

•Termination Unsaturated (C-C double bond)

(ethylene based monomers)

2.Classification by Polymerization Mechanism

Condensation polymers are obtained by random reaction of two molecules.

A molecule participating in a condensation reaction may be a monomer, oligomer, or high molecular

weight intermediate each having complementary functional end units, such as carboxylic acid or

hydroxyl groups. Typically condensation polymerizations occur by the liberation of a small molecule in

the form of gas, water, or salt.

More recently, another classification scheme based on polymerization kinetics has been adopted

over the more traditional addition and condensation categories.

• Step growth

• Chain growth

3.Classification by Polymer Structure

Classification by Chain structure (molecular architecture)

The architecture of the polymer is often physically determined by the functionality of the monomers

from which it is formed. This property of a monomer is defined as the number of reaction sites at which

may form chemical covalent bonds.

bifunctional

bifunctional bifunctional

3.Classification by Polymer Structure

Classification by Chain structure (molecular architecture)

(a) linear

(c) network

Branched polymers have side chains, or branches, of significant

points (known as junction points), are characterized in terms of the

number and size of the branches

The basic functionality required for forming even a linear chain is two

bonding sites.

Higher functionality yields branched or even crosslinked or networked

polymer chains.

(b) branch

Network polymers have three dimensional structures in which each

chain is connected to all others by a sequence of junction points and

other chains. Such polymers are said to be crosslinked and

characterized by their crosslink density, or degree of crosslinking,

which is related to the number of junction points per unit volume

Non linear polymers may be formed by polymerization, or can be prepared by linking together (ex.

crosslinking) pre-existing chains.

(d) ladder polymer

2.Classification by Polymer Structure

Classification by Chain structure (molecular architecture)

Ladder polymers constitute a group of polymer with a regular sequence of crosslinks.

diacetylene

2.Classification by Polymer Structure

Classification by Chain structure (molecular architecture)

(g) dendrimer

Dendrimers are repeatedly branched, roughly

spherical large molecules.

4.Classification by Polymer Structure

Classification by Monomer Composition

contain only one type of repeat unit (A))-A. Homopolymer

contain two different repeating units (AB)-B. Copolymer

If there are three chemically different repeating unit, it is then called terpolymer

Poly(styrene-co-acrylonitrile) (SAN)

Type of Copolymers

Random copolymer : -A-B-B-A-B-A-A-B-

-two or more different repeating unit are distributed randomly

Alternating copolymer : -A-B-A-B-A-B-A-B-

-are made of alternating sequences of the different monomers

Block copolymer : -A-A-A-A-B-B-B-B-

-long sequences of a monomer are followed by long sequences of

another monomer

Graft copolymer : -A-A-A-A-A-A-A-A-

-Consist of a chain made from one type of monomers with branches

of another type

B-B-B-B-B-

5.Classification by Thermal Behavior

A thermoset is a polymer that, when heated, undergoes a chemical change to produce a

cross-linked, solid polymer.( Ex: urea-formaldehyde, phenol-formaldehyde, epoxies)

Thermoplastic polymers soften and flow under the action of heat and pressure. Upon

cooling, the polymer hardens and assumes the shape of the mold (container).

(Ex: polyethylene, polystyrene, and nylon)

6.Classification by Preparative Technique

A) Bulk polymerization-only the monomer (and possibly catalyst and initiator, but no solvent) is

fed into the reactor. The monomer undergoes polymerization, at the end of which a (nearly) solid

mass is removed as the polymer product.

B) Solution Polymerization- involves polymerization of a monomer in a solvent in which both

the monomer (reactant) and polymer (product) are soluble

C) Suspension Polymerization- refers to polymerization in an aqueous medium with the

monomer as the dispersed phase. Consequently, the polymer resulting from such a system forms

a solid dispersed phase.

D) Emulsion Polymerization- is similar to suspension polymerization but the initiator is located

in the aqueous phase (continuous phase) in contrast to the monomer (dispersed phase) in

suspension polymerization.

Inorganic Polymers

polydimethylsiloxane

O Si

CH3

CH3

n

N P

Cl

Cl

n

Poly(dichlorophosphazene)

Polyelectrolytes

H2C

HC

COOH

n

H2C C

COOH

n

CH3

Poly(acrylic acid) Poly(methacrylic acid)

MOLECULAR WEIGHT

A number-average molecular weight Mn : divide

chains into series of size ranges and then determine the

number fraction Ni of each size range

where Mi represents the mean molecular weight of the

size range i, and Ni is the fraction of total number of

chains within the corresponding size range

A weight average molecular weight Mw is based on

the weight fraction wi within the size range.

Mn = ∑ Mi Ni / ∑ Ni

Mw = ∑ Mi Wi / ∑ Wi

The degree of polymerization represents one way of quantifying the molecular length or size of

a polymer. This can also be done by use of the term molecular weight (MW). By definition,

MW(Polymer) = DP × MW(Repeat Unit).

A measure of the molecular-weight distribution is given by the ratios of molecular

weight averages.

For this purpose, the most commonly used ratio is Mw/Mn, which is called the

polydispersity index or PDI.

PDI= Mw/Mn

Mw/Mn = 1 monodisperse

Polymer sample consisting of molecules all of which have the same chain length.

Mw/ Mn > 1 polydisperse

Polymer consisting of molecules with the variety of chain length

Polydispersity Index (PDI)

A. Types of Nomenclature

a. Source name : to be based on names of corresponding monomer

Polyethylene, Poly(vinyl chloride), Poly(ethylene oxide)

b. IUPAC name : to be based on CRU, systematic name

Poly(methylene), Poly(1-chloroethylene), Poly(oxyethylene)

c. Functional group name :

According to name of functional group in the polymer backbone

Polyamide, Polyester

Nomenclature

d. Trade name : The commercial names by manufacturer Teflon, Nylon

e. Abbreviation name : PVC, PET

f. Complex and Network polymer : Phenol-formaldehyde polymer

Nomenclature

Vinyl polymers

A. Vinyl polymers

a. Source name : Polystyrene, Poly(acrylic acid),

Poly(α-methyl styrene), Poly(1-pentene)

b. IUPAC name : Poly(1-phenylethylene), Poly(1-carboxylatoethylene)

Poly(1-methyl-1-phenylethylene), Poly(1-propylethylene)

CH2CH

Polystyrene Poly(acrylic acid)

Poly(α-methylstyrene) Poly(1-pentene)

CH2C

CH3

CH2CH

CO2H

CH2CH

CH2CH2CH3

B. Diene monomers

Source name : 1,2-Poly(1,3-butadiene) 1,4-Poly(1,3-butadiene)

IUPAC name : Poly(1-vinylethylene) Poly(1-butene-1,4-diyl)

CH2CH CHCH 2CH2CH

HC CH2

1,2-addition 1,4-addition

Vinyl polymers

Vinyl copolymer

Type Connective Example

Unspecified -co- Poly[styrene-co-(methyl methacrylate)]

Statistical -stat- Poly(styrene-stat-butadiene)

Random -ran- Poly [ethyelene-ran-(vinylacetate)]

Alternating -alt- Poly[styrene-alt-(maleic anyhride)]

Block -block- Polystyrene-block-polybutadiene

Graft -graft- Polybutadiene-graft-polystyrene

* A statistical polymer is one in which the sequential distribution of the monomeric units obeys the statistical laws. In the case of random copolymer, the

probability of finding a given monomeric unit at any site in the chain is independent of the neighboring units in that position.

Polystyrene-graft-polybutadiene

Polystyrene-block-polybutadiene

* Representative Nomenclature of Nonvinyl Polymers

Poly(hexamethylene Poly(iminohexane-

sebacamide) or Nylon6,10 1,6-diyliminosebacoyl)

Monomer Polymer Source or IUPAC name

structure repeating unit Common Name

O

H2C CH2

HOCH2CH2OH

H2N(CH2)6NH2NH(CH2)6NHC(CH2)8C

O O

HO2C(CH2)8CO2H

Poly(ethylene oxide)

Poly(ethylene glycol) Poly(oxyethylene)

Poly(oxyethylene) CH2CH2O

CH2CH2O

Abbreviations

Abbreviation Name

PVC Poly(vinyl chloride)

HDPE High-density polyethylene

LDPE Low-density polyethylene

PET Poly(ethylene terephthalate)

ABS Arcylonitrile-butadiene-styrene resin

PBT Poly(butylene terephthalate)

PE Polyethylene

PMMA Poly(methyl methacrylate)

PP Polypropylene

PS Polystyrene

PTFE Poly(tetrafluoroethylene)

PEO Poly(ethylene oxide)