1

1.1 Basic Polymer Chemistry Polymers are the largest class of soft materials: over

100 billion pounds of polymers made in US each year

Classification systems

Mechanisms of chain growth

1.2 Polymer Nomenclature Polymer =

Monomer =

Polymer =

Typical physical state?

Oligomer =

Typical physical state?

Polymerization =

1.3 Polymer Synthesis Two synthetic methodsChain growth/addition polymerization

Step growth polymerization

1.4 Chain Growth Polymerization Addition polymerizationOne molecule adds to another with no net loss of

atoms (high atom economy) Individual steps are typically rapid (msec, sec)Discrete steps

Propagation rate >> termination rateWhat happens if the reaction runs longer?Do the chains get longer?Do you just get more chains?

2

1.5 Chain Growth Polymerization Addition polymerizationWhat’s in the polymerization mixture?

Useful monomers for chain growth

nCH2 CH (CH2 CH)n

Monomer Polymer

X X

nCH2 CH

X

O

(CH2 CH

X

O)n

1.6 Monomers for Chain Growth Polymers form by…

Defining features

H2CCH2

H2CCH

H2CCH

Cl

H2CCH

CH3

ethylene styrene vinyl chloridepropylene

H2CCH

OCO

CH3

H2CC

C

CH3

O O-CH3

H2CCH

HCCH2

H2CCH

C

vinyl acetate methyl methacrylate butadiene acrylonitrile

N

1.7 Chain Growth Polymerization Mechanisms to link monomers togetherRadicalCationicAnionicTransition metal catalysis

2.1 Radical Polymerization Three steps to radical polymerization Initiation

RO OR 2 RO(1)

Propagation

RO

RO OR

H2C CH

R

CH2 CH

R

RO+

( )

(2)

CH2 CHRO + H2C CH CH2 CHRO CH2 CH

Termination

R R R R

3

2.2 Radical PolymerizationInitiation Propagation

RO CH CHRO CH CHRO CHpolystyrene

Head attacks the tail of the next monomer What defines the “head”? Why would RO• attack the tail preferentially?

ROH2C

CHCH2

CHROH2C

CHCH2

CHROCH2

CH

styrene

Initiation Propagation

Propagation continues until …

H2CCH

Cl

ROCH2

CH

Cl

ROH2C

CH

Cl

CH2

CH

Cl

ROCH2

CH

Cl

vinyl chloride

polyvinylchloride

Initiation Propagation

2.3 Radical Polymerization TerminationRadical Coupling

Disproportionation (H abstraction)

2.4 Radical Polymerization Chain transfer

2.5 Radical Polymerization Another “termination” mechanism “back-biting”

CH

CH2

CH2

CH2

CH2

H

CH

CH2

CH2

CH2

CH3

CH2 CH2 CH

C4H9

CH2 CH2

This is a prominent type of branch. Why would this be so?

4

2.6 Radical Polymerization Another termination process (chloroalkanes)

RO (CH2 CH)n

R

CH2 CH

R

+ CCl4 RO (CH2 CH)n

R

CH2 CH

R

Cl

CCl+ CCl3

CCl3 + CH2 CH

R

Cl3C CH2 CH

R

2.7 Radical Polymerization Monomers for radical polymerization

CH C C CH

F Cl Cl

H2CCH2

CC

H2CC

H2CCHF

F

F

Cl

HCCH2N

O OCH3

ethylene1,1,2,2-tetrafluoroethylene

vinylchloride1,1-dichloroethylene

H2CCH H2C

CH

HC

H2CCH

C

H2CC

C

CH3

O OCH3

styrene methylmethacrylate acrylonitrile 1,3-butadiene

2.8 Radical Diene PolymerizationReaction:

nCH2 CH CH CH2 (CH2 CH CH CH2)n

1,3-butadiene polybutadiene1,3 butadiene polybutadiene

Mechanism:

(1) ROOR 2RO

(2)

(3)

RO + CH2 CH CH CH2

RO CH2 CH CH CH2 + CH2 CH CH CH2

RO CH2 CH CH CH2

RO CH2 CH CH CH2 CH2 CH CH CH2

then (3), (3), (3), etc.

2.9 Radical Polymerization Accounts for about ½ of all commercial polymerization

What polymer structure forms when propylene is subjected to a radical process?subjected to a radical process?

Ethylene forms high molecular weight polymer but only under extreme conditions – why?

Product is highly branched (where do the branches come from?)

Is it possible to make linear PE?

5

3.1 Cationic Polymerization Initiating and propagating species are cationsMonomer attributes?

Cationic polymerization of isobutene (2-methylpropene)

HH2C

C

CH3

CH2

C

CH3

HCH3H2C

C

CH3

CH3CH3

Chain t i ti b

Initiation Propagation

isobutene or isobutylene

polyisobutyleneCH2

C

H3C

HCH2

C

CH3

CH3

CH3

H2CC

CH3

CH3

termination by loss of H+

What forms?Propagation

3.2 Anionic Polymerization Initiator and propagating species are anions

RH2C

CHCH2

CHRH2C

CHCH2

CHRCH2

CH

t

polystyrene

Initiation Propagation

H2CCH

CN

RCH2

CH

CN

RH2C

CH

CN

CH2

CH

CN

RCH2

CH

CN

styrene

acrylonitrile

polyacrylonitrile

3.3 Anionic Polymerization Monomer attributes?

Other example of monomers?

Chain termination

CH2

CHRCH2

CH

polystyrene

CH2

CH

n

H2O

CH2

CHRCH2

CHCH2

CH

n H+ OH

3.4 Living Polymerization What’s a “living polymer”?

6

4.1 Copolymers Random copolymers

SBR (styrene-butadiene rubber)

nCH2 CH

+ > nCH2 CH CH CH2

CH2 CH CH2 CH CH CH2 CH2 CH CH CH2

4.2 Copolymers ABS = acrylonitrile-butadiene-styrene terpolymer

CH2 CH

CN

+ CH2 CH CH CH2 + CH2 CH

CN

CH2 CH CH2 CH CH CH2 CH2 CH

CN

Control the amount of each monomer that ends up in the polymer?

4.3 Copolymers Block copolymers

M h i d Mechanism and process

Styrene-butadiene block copolymer

S S S S S B B B S S S S S B B

4.4 Block Copolymers

Polystyrene

Polybutadiene

Polybutadiene framework held together g

(cross-linked) by clusters of polystyrene

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4.5 Copolymers Graft copolymers

Styrene-butadiene graft copolymerStyrene polymerization off polybutadiene backbone

CH2 CH CH CH CH2 CH CH CH CH2 CH CH CH2

CH2

CH

CH2

CH2

CH

CH2

Could you graft polybutadiene off a polystyrene backbone?

CH CH

5.1 Metal Catalyzed PolymerizationCoordination and Insertion

M = Cr, Ti, Zr, Hf, V, Fe, Co, Ni, Pd, Cu

CH2

H2C

M

L

L

CH2CH3

CH2

CH2

M

L

L

CH2CH3

CH2

CH2

H2CCH2

M

L

CH2CH3L

5.2 Ziegler-Natta CatalysisChain Growth – Polyethylene (Polyethene)

CH2

H2C

ClCH CH

ClCH2CH3CH2CH3

Cl

Ti

Cl

CH2CH3

CH2

CH2

Ti

Cl

C 2C 3

CH2

CH2

H2 CH2CH3H2C

H2CCH2

Ti

Cl

C 2C 3

Ti

Cl

Cl

CH2CH3

CH2

CH2

CH2

H2C

H2CCH2

CH2

C

Ti

Cl

Cl

CH2

5.3 Ziegler-Natta CatalysisChain Growth – Polypropylene (Polypropene)

C

H2C

ClClCH3

H

Ti

Cl

Cl

CH2CH3

CH2

CHTi

Cl

Cl

CH2CH3

CH2

CH

H CH2CH3H2C

H2C

HC

Ti

Cl

CH2CH3Cl

CH3CH3

CH3

Ti

Cl

Cl

CH2CH3

H2C CH

CH

H2C

HCCH2

CH

H2C

Ti

Cl

Cl

CH2CH3H2CCH

CH3

CH3

CH3

CH3

CH3

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5.4 Ziegler-Natta CatalysisChain Termination with Hydrogen

CH2

H2CCl

PolymerH2CCH2C

H2

H2C

Cl

PolymerH2CCH2

H

HTi

Cl

H2CPolymerH2C

C

H

H

H

H2Ti

Cl

CH2CH2

Ti

ClH

H2C CH2

H2C

H

Ti

Cl

Cl

CH2

H2C CH2

Cl

H

Ti

Cl

Cl

CH2

5.5 Metal Complex Catalysis For polypropylene, the metal center can direct the

chain growth – MACROGALLERIA If one orientation is preferred …. then one polymer

t t i f d (i t ti )structure is preferred (isotactic)

CH2

C

CH2

C

CH2

C

CH2

C

CH2

C

CH2

H CH3 H CH3 H H HCH3 CH3 CH3

C C C CCH3 HCH3 H H CH3 HCH3 H CH3

isotactic:

CH2

C

CH2

C

CH2

C

CH2

C

CH2

C

CH2

CH2

C

CH2

C

CH2

C

CH2

C

CH2

C

CH2

CH3 H H CH3CH3 H CH3H CH3 H

atactic:

syndiotactic:

5.6 Polyethylene (PE) Types

HDPE 0.94 - 0.97High Density PE

Density (g/cc)

LLDPE 0.915 - 0.94Linear Low Density PE

LDPE 0.90 - 0.93Low Density PE

5.7 Ziegler-Natta Catalysis Used to make a variety of polymersHDPE = high density polyethyleneFormed by…y

Properties

CHH

CH2

H2CCH2CH3CH2

CH2 n

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5.8 Ziegler-Natta Catalysis LLDPE = linear low density polyethyleneHow are branches introduced?

How is the branch length changed?

How are the number and location of branches controlled?

CH2

H2CCH2

CH2

HCH2CH3CH2

CH

Rn

5.9 Ziegler-Natta Catalysis LLDPE = linear low density polyethylenemechanism

CHR

H2C

Ti

Cl

Cl

CH2CH3

CH2

CH2

Ti

Cl

Cl

CH2CH3

CH2

CH2

H C

H2C

CH2

Ti

Cl

CH2CH3Cl

Ti

Cl

Cl

CH2CH3

CH2

CH2

CHR

H2C

H2C

CH2

CH

H2C

Ti

Cl

Cl

CH2CH3H2C

CH2

R

5.10 ROMP Catalysis Metathesis

M CHR

L

L

H2C CHR

M CHR

L

L

H2C CHRM

CHRL

L

CH CHR+

H2C CHR H2C CHR CH2C

Ring Opening Metathesis Polymerization

M CH2

L

L M CH2

L

L M

L

L

M

L

L M

L

L M

L

L

6.1 Step Growth Polymerization Often referred to as condensation polymerizationNo free radical or ions are necessaryReactive functional groups

Polymer grows in multiple directions1:1 stoichiometry of functional groupsA—A + B—B A—A-B—B-A—A-B—B

New bonds formed during step growth polymerization

10

6.2 Step Growth Polymerization Often referred to as condensation polymerizationAtom efficient?

Reactions between functional groupsAmide (acid and amine) O

C

O

NH

Ester (acid and alcohol)Carbonate (alcohol and acid dichloride)Urethane (alcohol and isocyanate)

CO

OC

O

OO

C

O

NH

6.3 Step Growth Polymerization Polymerization mixture contains wide distribution of

slowly growing oligomers

n HO C

O

(CH2)4 C

O

OH + NH

(CH2)6 NH -H2On

PolyamideH H

C

O

(CH2)4 C

O

NH (CH2)6 NHn

adipic acid hexamethylenediamine (HMDA)

nylon 6,6

HO C

O

C

O

OH + HO CH CH OH-H2O

Polyamidediacid + diamine

poly(ethylene terephthalate)

n HO C C OH + n HO CH2 CH2 OH 2

C

O

C

O

O CH2 CH2 O

n

terephthalic acid ethylene glycolPolyester

diacid + dialcohol

6.4 Polyamides First synthetic polyamide was

poly(hexamethyleneadipamide), now called nylon 6,6 Reactants?

Mechanism?

n HO C

O

(CH2)4 C

O

OH + NH

H(CH2)6 N

H

H

-H2On

di i id (C ) h th l di i (C )

C

O

(CH2)4 C

O

NH (CH2)6 NHn

adipic acid (C6) hexamethylenediamine (C6)

nylon 6,6molecular weight = 10,000-25,000

n = 40-110

6.5 Nylon Nomenclature Double-numbered: 6,6 or 6,10First number = Second number =

Single-numbered: 4 or 6 or 12Number =

11

6.6 Two Routes to Polyesters

n HO C

O

C

O

OH + n HO CH2 CH2 OH-H2O

h h li id th l l l

high

n

C

O

C

O

O CH2 CH2 O

terephthalic acid ethylene glycol

O O

n CH3O C

O

C

O

OCH3

dimethyl terephthalate (DMT)

+ 2n HO CH2 CH2 OH -2n CH3OHlow

n

C

O

C

O

O CH2 CH2 O

6.7 Esterification Mechanism Polyester mechanism

HO C

O

C

O

OH HO C

O

C

OH

OH

+ HO CH2 CH2 OHH+

HO C

O

C

OH

OH

O CH2 CH2 OH

HHO C

O

C

OH

OH2

O CH2 CH2 OH-H2O

HO C

O

C

OH

O CH2 CH2 OH HO C

O

C O CH2 CH2 OH

O-H+

LeChatlier’s Principle

HO C C O CH2 CH2 OH HO C C O CH2 CH2 OH

6.8 Dendrimer 6.9 Polycarbonates Polycarbonates are strong, clear plastics

Carbonate = diester of carbonic acid Optical market (DVD, CD’s)

OCH3

(O C

CH3

CH3

O C)n

O

+ n Cl C

O

Cl-HCl

bisphenol Aphosgene

n HO C

CH3

CH3

OH

dialcohol + dichloride

12

7.1 Thermoset Polymers Linear polymers are typically thermoplasticSoften or melt when heatedCan dissolve (although sometimes with difficulty) in ( g y)

solventsChemistry to form the polymer takes place in the

polymerization reactorCan be melted and shaped (molded) into finished

articles without further chemistryThermoplastics are a collection of individualThermoplastics are a collection of individual

chains

7.2 Thermoset PolymersThermoset polymers are cross-linked

Chemistry to form the polymer takes place during formation (molding) of the final articleg ( g)The polymer “sets-up” or hardens within the mold

7.3 PolyurethaneReaction of an isocyanate and an alcohol yields

a urethane

Reaction of a diisocyanate and a diol (likeReaction of a diisocyanate and a diol (like polypropylene glycol) gives polyurethane

7.4 PolyurethanePoly(propylene glycol) is formed by base

catalyzed ring opening of propylene oxide with propylene glycol (diol)

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7.5 PolyurethaneReaction of polypropylene glycol (diol) and

toluenediisocyanate gives linear polyurethane

Urethane linkage

7.6 PolyurethaneReaction of a triol and toluenediisocyanate

yields a rigid cross-linked polyurethaneCH2O C

O

NH CH3

C2H5 C

CH2OH

CH2OH

CH2OH

trimethylolpropane

+ O C N

N C O

CH3 C2H5

CH2O C NH

N C O

CH3

C CH2O C

O

NH

N C O

CH3

CH2O C

O

NH

N C O

CH3TDI

CH2OH

CHOH

CH2OH

glycerol

+ 3n CH2 CH

CH3

Opropylene oxide

KOH

CH2O (CH2 CH

CH3

O)n CH2 CH

CH3

OH

CHO (CH2 CH

CH3

O)n CH2 CH

CH3

OH

CH2O (CH2 CH

CH3

O)n CH2 CH

CH3

OH

N C O

7.7 Phenol-Formaldehyde Polymers Leo Baekeland discovered the polymerization

of formaldehyde and phenol to give phenolicresins

Primarily used as a wood adhesive

CH2 CH2 CH2 CH2

OH

OH

HO

CHHO CH2 CH2

OH

CH2

CH2

CH2HO

CH2

CH2

bakelite

7.8 Two Component Epoxy Resins1. Low molecular weight polymer with epoxy end groups2. Curing agentEthylenediamine reacts with epoxy end groups on

l l l i ht llow molecular weight polymer

NH2 CH2 CH2 NH2

OO+ CH2 CH X CH CH2

N CH2 CH

OH

X CH

OH

CH2 N CH2 CH2 N CH2 CH

OH

X CH

OH

CH2 NN CH2 CH X CH CH2 N CH2 CH2 N CH2 CH X CH CH2 N

CH2

CH OH

X

CH OH

CH2

N

CH2

CH OH

X

CH OH

CH2

N