chemistry 367l/392n macromolecular chemistry lecture 7
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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.