radical copolymerization

Hanyang Univ.Hanyang Univ.

Spring 2008

Radical copolymerization Radical copolymerization

Regular copolymerRegular copolymer

Random copolymerRandom copolymer

Block copolymerBlock copolymer

Graft copolymerGraft copolymer

Actual copolymer (case)Actual copolymer (case)

Chap 11. Free Radical Copolymerization


Spring 2008

Only Binary CaseTwo Monomers; M1 + M2

+ M1

k11M1.

+ M2 M2

k12

k21

k22M2.

M2. +

+

M1

M2 M2.

.

.

.

M1

M1

.M1

Steady State Assumption

0][][ 21

dt

Md

dt

Md

]][[]][[ 12212112 MMkMMk

][

][

][

][

212

121

2

1

Mk

Mk

M

M

……①

Copolymer Equation

and chain transfer & termination compared w/ propagation


Spring 2008

]][[]][[][

122111111 MMkMMk

dt

Md

Instantaneous ratio of monomers in copolymerInstantaneous ratio of monomers in copolymer

]][[]][[][

222221122 MMkMMk

dt

Md

]][[][

]][[][

][

][

][

][

2221112

1221111

2

1

2

1

MMkMk

MMkMk

M

M

Md

Md

……②

][

][1

][

][1

][

][

1

22

2

11

2

1

M

Mr

M

Mr

Md

Md

monomer reactivity ratiomonomer reactivity ratio

From and ① ②

where 12

111 k

kr

, 21

222 k

kr

Copolymer Eq.

Copolymer Equation


Spring 2008

11 r then homopolymerization growth is preferred

01 r then only reaction with 2 will occur

f1, f2 : mole fractions of monomers in feed

F1, F2 : mole fractions of monomers in polymer

][

][1

21

121 MM

Mff

][][

][1

21

121 MdMd

MdFF

……④

Meaning of r & Definition of f1, F1

Meaning of r

Define f1, F1

22221

211

212

111

2 frfffr

fffrF

From , ③ ④

How come? How come?

…… ③

……⑤

characterizes the reactivity of the 1 radical with respect

to the two monomers, 1 and 21r


Spring 2008

][][

][][

][

][

][

][

221

211

2

1

2

1

MrM

MMr

M

M

Md

Md

1

2

1

rr

][][

][][

][

][

211

211

2

11 MMr

MMr

M

Mr

][

][

2

11 M

Mr

211

111 ffr

frF

1

21

22

12

11 k

k

k

k

22

21

12

11

k

k

k

k

Ideal Copolymerization


21 1 rr When , the two monomers show equal reactivity toward both propagating species random copolymer

121 rr

Most ionic copolymerizations are characterizes by the ideal type of behavior

where


Spring 2008

11 r 12 r or 11 r 12 r One of the monomer us nire reactive than

The other toward both propagating spices. The copolymer will contain a larger proportion ofthe more reactive monomer in random placement

F1

0 f1


For further details about Ideal Copolymerization

Click next homepage.

http://www.chem.rochester.edu/~chem421/copoly.htm

Surfing to the internet

1

1


Spring 2008

021 rr

f1

r1=0

F1 0.5

021 rr

As r1, r2 approach to zero, alternating tendency can be observed

perfect alternation!

1][

][

2

1 Md

Md][][

][5.0

21

11 MdMd

MdF

][][

][5.0

21

11 MdMd

MdF

Alternating Copolymerization


11 r , 12 r plots cross the line representing11 fF

21 rr , then, become a homopolymer

021 rror

→If

If

If

11 / fF

Cross-over point

1

1 0


Spring 2008

11 fF

At these crossover points the copolymer and feed compositions are the same and copolymerization occurs without a change in the feed composition

Such copolymerizaions are termed Azeotropic copolymeriztionsAzeotropic copolymeriztions.

Condition of Azeotropic copolymeriztion

][

][

][

][

2

1

2

1

M

M

Md

Md and )1(

)1(

][

][

1

2

2

1

r

r

M

M


Mean of Cross-over Point

121

1

21

11 ][][

][

][][

][f

MM

M

MdMd

MdF

∵


Spring 2008

][][

][][

][

][

][

][

221

211

2

1

2

1

MrM

MMr

M

M

Md

Md

][][][][ 221211 MrMMMr

22

1

2

11 ][

][1

][

][r

M

M

M

Mr

1

1

][

][

1

2

2

1

r

r

M

M

][][

][

21

11 MM

Mf

1

2

1

11

][

][1

1

2

12

2

1

1

2

1

r

rr

r

r

M

M

f

21

2

12

21 2

1

2

1

rr

r

rr

rf

∴



Spring 2008

21 rr ( 11 r and 11 r ) Both types of propagating species preferentially add monomer M1. there is a tendency toward consecutive Homopolymerization of the two monomers.And then monomer M2 will subsequently homopolymerize.

f1

r1>1

r1=1

r1<1

F1 In the result r1r2=1 ideal or random

f1

r1=2

r1=0

F1

fix r2=0.5

12

111 0

k

kr Addition monimer A and A*

Can not prepare copolymer

It’s alternating up to 0.5, and above 0.5 there’s no formation of copolymer



Spring 2008

f1

r1=0.5

F1

r2=0.5

azeotropic comp

alternating

f1

r1=2

r1=1

F1 r2=0.5

r1=1 no azeotrope

f1

F1 r1, r2 > 1 Case

tend to be a block copolymerization



Spring 2008

Drift: r1, r2 > 1 block azeotrope

r1, r2 <1 alternating

11 r,

12 r finally 121 rr Block COPOLYMERIZATION

HW #6.

Solve S.S. expression for a monomer concentration and substitute into the

original composition equation which contains the active center. You can get eq.

in terms of active center concentrations and if necessary define new kind of new

reactivity ratio in eq.



Spring 2008

1

][

][1

][

][

][

][

2

11

1

2

2

12 M

Mr

Md

Md

M

Mr

monomer comp

][][ 21 MM

copolymer comp.

][][ 21 MdMd

then vary r1 value (put) and iterate

12 rr experiment 3

experiment 2

experiment 1

This Δ is more for

smaller, r1, r2 value

calculate with accuracy

1.Mayo and Lewisrearrange copolymer eq. and can get

Experimental Determination of r1 & r2



Spring 2008

2. Finemann and Ross

Recall 2

22212

11

212

111

2 frfffr

fffrF

1211

12

12

11

11

)1(

)1(

)1(

)21(r

fF

Ffr

fF

Ff

A const.

Bconst.

at low conversion

A

B

r1

r2


Slope : r1

Intersection : r2


Spring 2008

11 ][)]([ FMdfMd

Material Balance for M1

where [M] = total # of moles of monomers

1111 ][][]}[{)]([ dfMMdfFMdfMd

111 ][][)( dfMMdfF

11

1

][

][

fF

df

M

Md

f

f fF

df

M

M0,1

11

1

0 ][

][ln

decrease of M1 monomer

ff fF

df

eM

M 0,111

1

1][

][1

0

Relationship Between ξand F1, f1

Relationship Between ξ and F1, f1


Spring 2008

Effect of Reaction Condition

Reaction medium

Temperature

Pressure

Reactivity

Depend on Solubility, PH, Viscosity, and Polarity

12

111 k

kr ]

)(exp[ 1112

12

11

RT

EE

A

A

But the effect of temperature on r is not large

RT

VVdf

dP

rd )(ln 211111

But the effect of pressure on r is not large

Next page


Spring 2008

I. Resonance StabilizationII. Polar EffectsIII. Steric Effects

I.Resonance Stabilization

Substituenton Double Bond

Relative Reactivityof Monomer

Stabilization Energy, kcal/mole

Olefine Radical

-H, -OCH3 1 0 0

-OAc, -CH3 1.5-5 2.5 4

-Cl 3-20 - 6

-COO, -COOH 20-60 2.5 -

-CN, -COR 30-60 0 -

-C2H3, -C6H5 50-100 3-4 25* Walling’s “Free Radicals in Solution”

Effect of Reaction Condition

Structure and Reactivity


Spring 2008

Define

rA, rB : monomer reactivity ratios

RA, RB : active center reactivity ratios

AB

AAA k

kr

BA

BBB k

kr

BA

AAA k

kR

AB

BBB k

kR

BA

BB

BB

AAB

BB

AAA k

k

k

kr

k

kR

AAA

BBB r

k

kR



Spring 2008

TABLE I. Propagation Rate Constants, Monomer Reactivity Ratios, and Active Center Reactivity Ratios for Radical Chain-Growth Polymerizations1

Mon A2 Mon B2 KAAx10-3 KBBx10-3 rA rB RA RB

ANANANANMAMAMAMMAMMASTY

MAMMASTYVAMMASTYVASTYVAVA

1.961.961.961.962.092.092.09

0.5150.5150.515

2.090.5150.1652.30

0.5150.1652.30

0.1652.302.30

1.260.150.045.4

0.250.20

9.0.462055

0.671.200.40

0.0503.220.750.1

0.520.0150.01

6.28x10-1

4.57x100

4.8 x100

4.3 x10-2

1.31x101

9.5 x100

9. x10-2

1.6 x100

3.4 x10-3

7. x10-4

1.34 x100

3.94 x10-2

3.4 x10-3

6.3 x100

6.16 x10-2

1.6 x10-2

1. x101

1.5 x10-1

8.9 x101

8. x102

1All values are based on data collected at 60℃2AN=acrylonitrile; MA=methylacrylate; MMA=methylmetacrylate; STY=styrene; VA=vinyl acetate



Spring 2008

Active Center Reactivity Ratios vs. Monomer Reactivity Ratios

*][*][

*][*][

*][

*][

][

][

BRA

BAR

B

A

Bd

Ad

B

A

BA

AAA k

kR

AB

BBB k

kR

when BA RR then BA rr

A

B

B

A

r

r

R

R when BA RR

The effect in relative reactivity of the active center is more stronger than that of monomer.

The monomer reactivity gets affect in opposite way comparing to the active center reactivity.



Spring 2008

Odian Table 6-3. Relative Reactivities(1/r) of Monomers

MonomerPolymer Radical

Butadiene Sty VAc VC MMA MA AN

Butadiene 1.7 29 4 20 50

Styrene 0.7 100 50 2.2 5.0 25

Methyl Metacrylate 1.3 1.9 67 10 2 6.7

Methyl Vinyl Ketones 3.4 20 10 1.7

Acrylonitrile 3.3 2.5 20 25 0.82 1.2

Methyl Acrylate 1.3 1.3 10 17 0.52 0.67

Vinylidene Chloride 0.54 10 0.39 1.1

Vinyl Chloride 0.11 0.059 4.4 0.10 0.25 0.37

Vinyl Acetate 0.019 0.59 0.05 0.11 0.24



Spring 2008

@ Substituent Effects

Φ, CH2=CH- > -C≡N, -COR > -COOH, -COOR > -Cl > -O-COR, -R > -OR, -H

monomers increase relative reactivity by resonance stabilization.The resonance stability of the monomer increases the reactivity of the monomer.

The resonance stability of the radical is weakened reactivity of the radical.Table 6-4 Rate Constant(k12) for Radical-Monomer Reactions

Polymer Radical

Monomer(M1) Buta-diene

Sty-rene

Methyl Metacrylate

Acrylo-nirile

Methyl Acrylate

Vinyl Acetate

Vinyl Chloride

Q1 e1

ButadieneStyreneMethyl _methacrylateAcrylonitrileMethyl _acrylateVinyl chlorideVinyl acetate

10070

130330

13011

280165

314413

2159.73.4

2,0601,130

515422

2685226

98,00049,000

13,1001,960

1,310720230

41,80010,045

4,1802,510

2,090520530

230,000154,000

46,00023,000

0,1002,300

319,000550,000110,000225,000187,00011,0006,490

2.391.000.740.600.420.0440.026

-1.05-0.800.401.200.600.20-0.22



Spring 2008

Resonance stabilization of Active Center

CH2

C CO

OR

H

. CH2

CH

CO

OR

.

Transition State Theory

AB* Activated complex

ΔER A + B

compound

Increasing Separation of A & B


ΔHR

P.E.


Spring 2008

P.E.

AB Morse curve

A+B repulsion curve

Increasing Separation of A & B

P.E.

Reaction III R

Reaction I R

Increasing Separation of Reactant

R


ΔE1‡ > ΔE3‡ then Rxn III is less stable than Rxn IΔHR3‡ < ΔHR1‡

ΔE1‡ΔE3‡

R + M

Rs + M


Spring 2008


Resonance stability of Active Center becomes primary

Resonance stability of Monomer becomes secondary

Resonance stability of Active Center becomes primary

Resonance stability of Monomer becomes secondary


Spring 2008

-ΔH ΔE‡

R·+ MS → RS· 1.20 0.40

R·+ M → R· 0.95 0.50

RS·+ MS → RS· 0.70 0.70

RS·+ M → R· 0.40 0.80

|-ΔH | > > > ① ② ③ ④

ΔE‡ > > > ④ ③ ② ①


For further details about Free Radical Polymerization

Click the link below.

http://www.chem.rochester.edu/~chem421/frfull.htm



Spring 2008

Tend to cause alternation in a copolymerizationi.e.

1 BA rr 1 BA rr for polar effects

(Polarity Values)

e : tendency to give monomer a polar effects Alfrey-Price Q,e scheme

Structure and Reactivity II. Polar Effects


Spring 2008

Ar , Br forecast randomness of copolymerization

)exp( jijiij eeQPk

where P : active center reactivity Q : monomer reactivity i, j : active center, monomer, respectively

As know r, prediction is possible to polar, resonance effect Guidance to chemists

)exp(

)exp(

jiji

iiii

ij

iii eeQP

eeQP

k

kr

)](exp[ jiij

ii eee

Q

Qr


@ Q-e scheme of Alfred Price


Spring 2008

ir

(arbitrary)

So that, this equation forecasts

Base materials use styrene : 1Q

8.0e

fair results, but not absolute in predicting r using Q-e scheme.

)](exp[)exp(

)exp(ijj

i

j

ijji

jjjj

ji

jjj eee

Q

Q

eeQP

eeQP

k

kr

])(exp[)](exp[

)](exp[ 2ji

ijj

jiiji ee

eee

eeerr

1])(exp[ 2 jiji eerr

0)(0)( 22 jiji eeee

alternating tendency is correct



Spring 2008

Active Center Reacting Ratios

*][*][

*][*][

*][

*][

][

][

BRA

BAR

B

A

Bd

Ad

B

A

P-e scheme

ji

ii

ijij

iiiii k

k

eeQP

eeQPR

)exp(

)exp(

)](exp[ jiij

ii eeeP

PR

P e Q E

StANMAMMAVAc

158.2321.032.413751.3

-0.81.2330.5770.397-0.027

10.4

0.420.24

0.024

-0.81.21.20.4

-0.22



Spring 2008

The criticism against Q-e schemeReference state arbitrarily set.Alternating effect was observed due to fixed charges not due to the induced dipole

Exercise)How to indicate Randomness of Copolymer with Q-e scheme ?

We can forecast alternation or randomness through Q-e scheme, however, why can not forecastBlockcopolymerization? (algebraic standpoint)



Click the link below

http://www.kcpc.usyd.edu.au/resources/notes/gilbertnotes3.pdf



Spring 2008

H

C C

R

H

R'

1) 1,2-disubstituted ethylene do not homopolymerize readily

Structure and Reactivity III. Steric Effects

2) 1,1-disubstituted ethylene

C

X X

CH2

CCH2

CCH2

C

X X X XX X

. + CH2 CX2

planar conformationtetrahedral conformationmore reactive

II. Polar Effects


Spring 2008

3) Cis-trans Effect

The trans is stabilized the cis than thermodynamics(Heat of Hydrogenation)

Planarity! Easier for trans than cisSteric Effect!

H

C C

X

H

X

H

C C

X

X

H



Click the link below.

http://pslc.ws/macrog/lab/unit1.htm



Spring 2008

Table 6-5 Rate Constants( 12k ) for Radical-Monomer Reactionsa

Monomer Polymer Radical

Vinyl Acetate

Styrene Acrylonitrile

Vinyl chlorideVinylidene chlorideCis-1,2-DichloroethyleneTrans-1,2-DichloroethyleneTrichloroethyleneTetrachloroethylene

10,000 23,000 365

2,320 3,480 338

9.7 89

0.79 4.5 10.3 0.83

725 2,150

29 4.2

a12k Values were calculated from data in Table 3-11 and 6-2 and [66]

1,1-disubs.Mono subs.

High reactive

Tri subs.Trans 1,2Cis 1,2


radical copolymerization

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