Chemistry 367L/392N

Macromolecular ChemistryMacromolecular Chemistry

Lecture 7 Lecture 7

N

NNN Cu+

BR-

Chemistry 367L/392N

Decomposition of Thermal InitiatorDecomposition of Thermal Initiator

OO N

N

CN

CNO

OO

O

O

O

di-tert-butylperoxide AIBN di-tert-butylperoxalatef = 0.65 f = 0.75 f=0.95

Ikfdt

Rdd

2•

Ri

Efficiency factor ( Efficiency factor ( ff ): ):

k dI → 2 R·

Chemistry 367L/392N

-- dd[[M·M·]]RRii== dtdt

== 2 2 kkt t [[M·M·]]22 Where kWhere ktt = k = ktctc+ k+ ktdtd

RRpp= = dtdt

--d[[MM]] = k= kpp[[MM][][M·M·]]

[[M·M·]]==

Kinetics of free radical polymerizationKinetics of free radical polymerization Steady state assumption:Steady state assumption:

What is the Propagation rate ( What is the Propagation rate ( RpRp ) )

22]][[22]][[22 MMkkIIfkfk ttdd

tt

dd

kk

IIfkfk ]][[

RRpp= = dtdt

-d-d[[MM]] = k= kpp[[MM]]

tt

dd

kkIIfkfk ]][[

So…So…

Ri = RtRi = Rt

Chemistry 367L/392N

Average kinetic chain lengthAverage kinetic chain length (( ӮӮ ))

  Disproportionation : Disproportionation :        Combination : Combination :

Kinetics of free radical polymerizationKinetics of free radical polymerization

ӮӮRR

RR

RR

RR

tt

pp

ii

pp

ӮӮ]][[((

]][[22

]][[22

]][[

]][[22]]][][[[

22 IIkkfkfk

MMkk

MMkk

MMkk

MMkk

MMMMKK

ddtt

pp

tt

pp

ttpp

DP =DP = 22ӮӮ

DP =DP = ӮӮ

Chemistry 367L/392N

The relationship between DP and conversionThe relationship between DP and conversionWith termination reactionsWith termination reactions

The chain growth systemThe chain growth system

Chemistry 367L/392N

TEMPO Controlled PolymerizationTEMPO Controlled Polymerization1993 M. K. Georges, R. P. N. Veregin, P. M. Kazmaier and G. K. Hamer (Xerox 1993 M. K. Georges, R. P. N. Veregin, P. M. Kazmaier and G. K. Hamer (Xerox Corporation), "Narrow Molecular Weight Resin by Free Radical Process."Corporation), "Narrow Molecular Weight Resin by Free Radical Process."

I

+ O N

IO N

Monomer

Polymer + O N

Polymer O N

DP =[monomer]

[Initiator]

(2,2,6,6-tetramethylpiperidinyl-1-oxy) TEMPO

Chemistry 367L/392N

Radical Chain GrowthRadical Chain GrowthChain polymerization with terminationChain polymerization with termination

Chain polymerization without terminationChain polymerization without terminatione.g. nitroxide-mediated radical polymerization

DP =[monomer]

[Initiator]

Life time of polymer radical chain is about 1 secondLife time of polymer radical chain is about 1 second

Initiator slowly decomposes throughout polymerization timeInitiator slowly decomposes throughout polymerization time

Steady State approximation:Steady State approximation:

rate of initiation = rate of terminationrate of initiation = rate of termination

Therefore, [propagating radical] remains constant Therefore, [propagating radical] remains constant

Initiator decomposes quickly (high temp)Initiator decomposes quickly (high temp)polymer chains have long life timespolymer chains have long life times

“Living”DP

50 100

conversion

DP

50 100

conversion

Chemistry 367L/392N

Controlled Free Radical PolymerizationControlled Free Radical Polymerization

Chemistry 367L/392N

Library of alkoxyaminesevaluated as initiators for the livingLibrary of alkoxyaminesevaluated as initiators for the living free radical polymerization of styrene and n-butyl acrylate. free radical polymerization of styrene and n-butyl acrylate.

Chemistry 367L/392N

TEMPO

Acrylates???Acrylates???

Chemistry 367L/392N

Published Example of Block Copolymer Formation

Ph

Ph

Ph

N

O

P

O

OEt

OEt

Ph

Ph

O

N P

O

OEt

OEt

O

OMe

Ph

Ph

O

O OMe

N

PO

O

O

AIBN, heat

SG1

n-1

n

+

SG1

n-1

m

n-1 m

D : n = 60 : m = 20

propagation

n = 60

m = 20

heat

Ph

PhO OMe

n-1 m

D : n = 60 : m = 20

Reversible trapping prevents irreversible termination

A living poly(styrene) block heated in the presence of methyl acrylate to give diblock D

Chemistry 367L/392N

Control of polymer ArchitectureControl of polymer Architecture

O

O

O

N

+

O

OCH3

AIBN

OO

OTEMPO

OOCH3

OOCH3

OOCH3

OO

OTEMPO

Chemistry 367L/392N

OO

OTEMPO

OOCH3

OOCH3

OOCH3

OO

OTEMPO

OO

OOCH3

OOCH3

OOCH3

OO

Ph

Ph

Ph

Ph

Chemistry 367L/392N

The relationship between Mwt and conversion

Step growth systemStep growth system

Chemistry 367L/392N

The relationship between MThe relationship between Mwtwt and conversion and conversionWith termination reactionsWith termination reactions

The chain growth systemThe chain growth system

Chemistry 367L/392N

The relationship between MThe relationship between Mwtwt and conversion and conversionWith no termination reactionsWith no termination reactions

The chain growth systemThe chain growth system

Chemistry 367L/392N

Other Controlled/Living Radical PolymerizationsOther Controlled/Living Radical Polymerizations

Nitroxide mediatedNitroxide mediatedstable free radicals e.g. TEMPOstable free radicals e.g. TEMPO

Atom Transfer PolymerisationAtom Transfer Polymerisation Cu(I)Br/LigandCu(I)Br/Ligand

RAFT RAFT thioesters/xanthatesthioesters/xanthates

Chemistry 367L/392N

K. Matyjaszewski: Macromolecules K. Matyjaszewski: Macromolecules 19971997, , 3030, p7697; 7042; 7034; 7348; 8161; 7692; 6507,, p7697; 7042; 7034; 7348; 8161; 7692; 6507,6513, 6398 JACS 6513, 6398 JACS 19971997, , 119119, p674, p674V Percec: Macromolecules V Percec: Macromolecules 19971997, , 3030, p6705, 8526, p6705, 8526M Sawamoto: Macromolecules M Sawamoto: Macromolecules 19971997, , 3030, p2244, 2249, p2244, 2249Teyssie: Macromolecules Teyssie: Macromolecules 19971997, , 3030, p7631, , p7631, Haddleton: Macromolecules Haddleton: Macromolecules 19971997, , 30, 30, p2190p2190

Atom Transfer Radical Polymerization - ATRPAtom Transfer Radical Polymerization - ATRP

R X + Metal (n) R + Metal (n + 1)

Br

++CuBr CuBr2

Chemistry 367L/392NMacromolecules, 30 (25), 7697 -7700, 1997Macromolecules, 30 (25), 7697 -7700, 1997..

N

NNN Cu+

BR-

ATRPATRP

ATRP works on Acrylates !!

Chemistry 367L/392N

Living Free-Radical Polymerization by ReversibleLiving Free-Radical Polymerization by ReversibleAddition-Fragmentation Chain Transfer: The RAFT Process Addition-Fragmentation Chain Transfer: The RAFT Process

Macromolecules, 31 (16), 5559 -5562, 1998Macromolecules, 31 (16), 5559 -5562, 1998

Magic Reagent

Chemistry 367L/392N

R' S

SR

A Dithionate

Radical addition to Dithionate estersRadical addition to Dithionate esters

R''

R' SR

SR''

R' S

SR''

+ R

Chemistry 367L/392N

S

S

CH3

CH3CH3

CH3

SI

S

O

O

CH3

n

SI

S

O

O

CH3

n

C CH3

CH3

I

O

O

CH3

C

OO

CH3

n-1 .

CH3

CH3

O

O

CH3

C

OO

CH3

m

O

O

CH3

KP

O

O

CH3

KP

I.

RAFT polymerisation ofMMA with 2-phenylprop-2-yldithiobenzoate (1).

(1)

K

Kadd

K-add

RAFT PolymerisationRAFT Polymerisation

Chemistry 367L/392N

Molecular weight distributions for poly(styrene-co-acrylonitrile) Molecular weight distributions for poly(styrene-co-acrylonitrile) polymerized by heating styrene and acrylonitrile (62:38 mole ratio) at 100 polymerized by heating styrene and acrylonitrile (62:38 mole ratio) at 100 C in the presence of cumyl dithiobenzoateC in the presence of cumyl dithiobenzoate

RAFT works!!RAFT works!!

Chemistry 367L/392N

FRONTIERS IN POLYMER CHEMISTRYFRONTIERS IN POLYMER CHEMISTRYVIRGIL PERCEC, GUEST EDITOR VIRGIL PERCEC, GUEST EDITOR

Chemical Reviews Volume 101, Issue 12 (December 12, 2001)

•Colored ProductsColored Products

•Strange Chain endsStrange Chain ends

•Metal ContaminationMetal Contamination

•The role of Cu in ATRPThe role of Cu in ATRP

•Sociology and psychologySociology and psychology

CRP - IssuesCRP - Issues

Chemistry 367L/392N

Measuring Molecular WeightMeasuring Molecular Weight Membrane Osmometry AlfredoAlfredo Vapor Phase Osmometry LindaLinda Viscometry Gel Permeation Chromatography

– Size exclusion Chromatography Light Scattering MALDI Others

– End group analysis , etc.

Chemistry 367L/392N

For normal (Newtonian) flow behaviour:

= (F/A) = . (dv/dy)

Definition of Definition of viscosity:viscosity:

/(dv/dy)

units: (dyne/cm2)/sec-1

= dyne.sec.cm-2. . = POISE (P)

At 20.0oC, (water) ~ 0.01P = 1.0 Centipoise

shear shear stressstress

shear shear raterate

viscosityviscosity

Chemistry 367L/392N

A dissolved macromolecule will INCREASE the viscosity of a solution because it disrupts the streamlines of the flow:

Viscosity of Polymer solutions:Viscosity of Polymer solutions:

Chemistry 367L/392N

UbbelohdeUbbelohde Viscometer Viscometer

Chemistry 367L/392N

1. “U-tube” (Ostwald or Ubbelohde)

2. “Cone & Plate” (Couette)

Types of Viscometers:Types of Viscometers:

Chemistry 367L/392N

We define the relative viscosityrelative viscosity rr as the ratio of the viscosity of the solution containing the macromolecule, , to that of the pure solvent in the absence of macromolecule, o:

r = o units?

For a U-tube viscometer, r = (t/to). (o)

Relative viscosity Relative viscosity rr

Chemistry 367L/392N

The The relative viscosityrelative viscosity depends (at a given depends (at a given temp.) on the concentration of temp.) on the concentration of macromolecules, the shape of the macromolecules, the shape of the macromolecule & the volume it occupies. We macromolecule & the volume it occupies. We can infer things about the shape and volume can infer things about the shape and volume of the macromolecule if we eliminate the of the macromolecule if we eliminate the concentration contribution.concentration contribution.

The first step is to define the The first step is to define the reduced viscosityreduced viscosity

redred = = rr – 1)/c – 1)/c

Where C is the concentration in gm/mlWhere C is the concentration in gm/ml

Reduced viscosityReduced viscosity

Chemistry 367L/392N

To eliminate non-ideality effects deriving from exclusion volume, backflow and charge effects, etc we by analogy with osmotic pressure, measure red at a series of concentrations and extrapolate to zero concentration:

] = Lim] = Limcc⃗⃗00 redred))

units [] = ?

The Intrinsic Viscosity [The Intrinsic Viscosity []]

Chemistry 367L/392N

Molecular Weight from [Molecular Weight from []]

Mark-Houwink-Kuhn-Sakurada equation

[[] = K’ M] = K’ Maa

a = 1.8a = 1.8

a = 0a = 0

a = 0.5-0.8a = 0.5-0.8

Chemistry 367L/392N

Representative Viscosity-Molecular Weight Constantsa

PolymerPolymer

Polystyrene(atactic)c

Polyethylene(low pressure)Poly(vinyl chloride)

Polybutadiene98% cis-1,4, 2% 1,297% trans-1,4, 3% 1,2Polyacrylonitrile

Poly(methyl methacrylate-co-styrene)30-70 mol%71-29 mol%Poly(ethylene terephthalate)Nylon 66

SolventSolvent

CyclohexaneCyclihexaneBenzeneDecalin

Benzyl alcoholCyclohexanone

TolueneTolueneDMFg

DMF

1-Chlorobutane1-ChlorobutaneM-CresolM-Cresol

Temp Temp ooCC

35 d

5025135

155.4d

20

30302525

30302525

Molecular WeightMolecular WeightRange Range 10 10-4-4

8-42e

4-137e

3-61f

3-100e

4-35e

7-13f

5-50f

5-16f

5-27e

3-100f

5-55e

4.18-81e

0.04-1.2f

1.4-5f

KKbb 10 1033

80 26.9 9.52 67.7

156 13.7

30.5 29.4 16.6 39.2

17.6 24.9 0.77240

aabb

0.500.5990.740.67

0.501.0

0.7250.7530.810.75

0.670.630.950.61

aValue taken from Ref. 4e. bSee text for explanation of these constants. cAtactic d temperature. Weight average. fNumber average. gN,N-dimethylformamide.