2013 Polymer Synthesis

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Polymers: Introduction

Polymer: High molecular weight molecule madeup of a small repeat unit (monomer).

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Monomer: Low molecular weight compound thatcan be connected together to give a poymer

Oligomer: Short polymer chain

Copolymer: polymer made up of 2 or more

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

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

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

Types of Polymers Polymer Classifications

Thermoset: cross-linked polymer that cannot bemelted tires rubber bands

Thermoplastic: Meltable plastic

Elastomers: Polymers that stretch and then return totheir original form: often thermoset polymers

Thermoplastic elastomers: Elastic polymers that canbe melted (soles of tennis shoes)

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o ymer am esPolyolefins: made from olefin (alkene) monomers

Polyesters, Amides, Urethanes, etc.: monomers linkedby ester, amide, urethane or other functional groups

Natural Polymers: Polysaccharides, DNA, proteins


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Natural PolymersMonomer Polymer

Isoprenen

Polyisoprene:

O

H

HO

H

HO

H

HOHH

OH

OH

Poly(-D-glycoside):cellulose

O

H

O

H

HO

H

HOHH

OH

OH

H

n

-D-glucose

H3N

O

O Polyamino acid:H3N

OHN

OHN

O

OH

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R protein1 n+1 n+2

Amino Acid

BaseO

OH

OPO

O

O

oligonucleic acidDNA

NucleotideBase = C, G, T, A

BaseO

O

OP

O

O

O

DNA

DNA

What Makes Polymers Unique? Really big molecules (macromolecules) like

polymers have very different properties than

Chain entanglement: Longpolymer chains get entangled witheach other.

When the polymer is melted, thechains can flow past each other.

Below the melting point, the chains

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can move, but only slowly. Thus theplastic is flexible, but cannot beeasily stretched.

Below the glass transition point, thechains become locked and thepolymer is rigid


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Polymer Synthesis

There are two major classes of polymer formationmec an sms

1. Addition polymerization: The polymergrows by sequential addition of monomers to areactive site

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Chain growth is linear

Maximum molecular weight is obtained earlyin the reaction

Polymer Synthesis

2. Step-Growth polymerization : Monomersreact together to make small oligomers. Smalloligomers make bigger ones, and bigoligomers react to give polymers.

Chain growth is exponential

Maximum molecular weight is obtained late

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in the reaction


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Anatomy of Addition Polymerizations

Initiation

Generation of active initiator

Azo (-N=N-)

Disulphide (-S-S)

Peroxide (-O-O)

Example :

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enzoy erox eAIBN

Reaction with monomer to form growingchains


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Anatomy of Addition Polymerizations

PropagationChain extension by incremental monomer

Chain Termination

Conversion of active growing chains to inertpolymer

Combination or disproportionation

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site by terminating one chain and reinitiating a

new chain.Chain transfer to monomer, to solvent and to

polymer

Addition Polymerization

In*A

InitiationIn A* A

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Addition PolymerizationPropagation

In*A

InitiationIn A A* A

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Addition PolymerizationPropagation

AIn*A

InitiationIn A A A*

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Addition Polymerization

Propagation

nAIn A A A A

nA*In*

A

InitiationIn A A A A*

A A A A Am

In A A A AnA

*A A A A Am

Combination

*A A A A Am

In A A A AnA

B A A A Am

Disproportionation

A

In A A A AnA

A*

Chain TransferNew reactive siteis produced

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TerminationReactive site is consumed

MWkpropagation

k termination

MW

% conversion0 100

Types of Addition Polymerizations

Ph

Anionic

C3H7 LiC4H9

Li+ Phn

C4H9Li+

n

Ph Ph Ph

Ph

Radical

PhCO2Ph

n

Cationic

PhCO2

Ph

PhCO2

Ph Phn

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PhCl3Al OH2

H

PhHOAlCl3

Phn

H

Ph Phn

HOAlCl3


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Branching: High and low density

Polyethylene

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Commodity Polyolefins

Pol ro lene (1954)

PP

dishwasher safe plastic ware, carpet yarn, fibers and ropes,

webbing, auto parts

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PIBinner tubes, flexible adhesives, raincoats

Commodity Vinyl Polymers

Pol st rene (1920)

PS

Styrofoam, clear plastic cups

envelop windows, toysCl

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PVC

garden hose, pipe, car trim, seat covers, records,

floor tiles


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Semi-Commodity Polymers

Pol (meth l methacr late) (1931)

CO 2CH 3

CO CH

CO 2CH 3

CO CH

CO 2CH 3

PMMA

plexiglas, embedding resin, resist for X-ray applications

FF F

FF

FF

F

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Polytetrafluoroethylene. (1943)

teflon, non stick cookware, no grease bearings,pipe-seal tape

FF

FF

FF

FF

Step-Growth PolymerizationStage 1

Consumptionof monomer

n n

Stage 2

Combinationof small fragments

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Stage 3

Reaction ofoligomers to givehigh molecularweight polymer


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Step-Growth Polymerization

Because high polymer does not form until the endof the reaction, high molecular weight polymer is

is achieved.

Xn 1

1p100

1000

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Xn= Degree of polymerizationp = mole fraction monomerconversion

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0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

Mole Fraction Conversion (p)

Nylon-6,6

Cl Cl

O O

4H2N NH24

Adipoyl chloride 1,6-Diaminohexane

Cl NH

NH

H

O O

4 4

NaOH

HO NH

NH

H

O O

4 4n

6 carbon 6 carbon

Adipoyl chloridein hexane

Nylon 6,6

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diacid diamineNylon-6,6

Diamine, NaOH, in H2O


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Nylon-6,6Since the reactants are in different

phases, they can only react at thephase boundary. Once a layer ofpolymer forms, no more reaction

Adipoyl chloridein hexane

Nylon 6,6

occurs. emov ng e po ymer a owsmore reaction to occur.

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Diamine, NaOH, in H2O

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Condensation Reaction

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Commodity Condensation Polymers

NC

O

NN

CC

OH

Nylon 6 /

bearings, molded parts

carpet yarn

marine rope

cookin /boilin ba s

Nylon 66 (1939)

Fibers, tire cord, fishing line

OH

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Commodity Condensation Polymers

O O

C

C

Polyester (1941)

PET, dacron, mylar, kodel

fibers, film-backing, magnetic tapes, soft drink bottles, tire

cord, moldings

O

O O

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o ycar ona e

PC, Lexan

shatter proof glass, cd-disks, car doors and roofs,

appliance housings

O

Polymer Categories: PriceCommodity $5/pound

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Semicrystalline Thermoplastic

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Crystalline Structures

Single CrystalsSingle Crystals PolymerPolymer SpherulitesSpherulites

48SharmisthaSharmistha DattaDatta & David J. W. Grant,& David J. W. Grant, Nature Reviews Drug DiscoveryNature Reviews Drug Discovery 3,3,4242--57 (January 2004)57 (January 2004)


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Two crystalline morphologies

(collections of lamellar crystalites)

Row Nucleated (shear )

Shish-kebab

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Polymer Categories: Network

Thermoset vs Thermoplastic

Network vs Linear

Fixed vs Reshapeable

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2013 Polymer Synthesis