polymer chemistry -...

Polymer Chemistry

Guangxi University School of Chemistry & Chemical Engineerin

g

Li Guang Hua (李光华)

Lab：材料楼—409#，321# E-mail : [email protected] phone: 15978133590

mailto:[email protected]

CHAPTER 4

1. Comparison of Radical and Ionic Polymerization

Ionic Polymerization:

2. Cationic Polymerization2.1 Cationic Initiators2.2 Mechanism2.3 Living Cationic Polymerization

Guangxi University School of Chemistry & Chemical Engineeri

ng

2.3 Living Cationic Polymerization

3. Anionic Polymerization3.1 Initiators and Initiation3.2 Mechanism and Kinetics3.3 Applications of Anionic Polymerization

(1)

1. COMPARISON OF RADICAL & IONIC PZN (I)

anionM

A

Ø Active Center

Ionic PZNcation

M A&counterion (反离子)gegenion (抗衡离子)

Free Radical PZN


ng(2)

Ø Monomer Selectivity

Ionic PZN : high monomer selectivity

R+

CH2 C

CH3

CH3CH2 CH

OR

O

O

conjugated vinyl monomer

O

O O

CH2=O

1. COMPARISON OF RADICAL & IONIC PZN (II)

Free Radical PZN : most vinyl monomers

R-CH2 C

COOCH3

CH3

CH2 CH

CN

OCH2=Oconjugated vinyl monomer


ng(3)

Ø PZN conditions

Ionic PZN : stringent

Purification of monomer & solventCalcining reactor

Temp.R+ : –100oC

R- : –78oC

Free Radical PZN : mild

1. COMPARISON OF RADICAL & IONIC PZN (III)

Ø Influence of solvent

Ionic PZN :

R AA RR A// +AR

covalent intimateion pair

solvent-separatedion pair solvated ions

increase


ng(4)

The influence factors of above equilibrium :

RP

Reactivity of propagating speciesincrease

isotactic syndiotactic

¹ Temp.¹ Solvating power (polar of solvent )

Free Radical PZN

1. COMPARISON OF RADICAL & IONIC PZN (IV)

Higher temp.Counterion don’t exist

Atactic polymer

Ø Termination Ionic PZN :¹ No termination by coupling


ng(5)

¹ No termination by coupling

¹ Self termination or termination by impurities

M M+

Free Radical PZN :¹ Termination by coupling or disproportionation

¹ Termination by chain transfer reactions

X

2. CATIONIC PZN (I)

InitiatorsFIn cationic PZN the propagating species is a carbocation. Initiation is

brought about by addition of an electrophile to a monomer molecule.

E + CH2 CR2 ECH2CR2

initiator


ng(6)

Ø Protonic acid (质子酸) : H2SO4, H3PO4, etc.

AlCl3, BF3, TiCl4, SnCl4

Ø Lewis acid :

+ H2O or RX (coinitiator)

AlCl3 + RCl AlCl4R

(HOBF3)H + H2OBF3

2. CATIONIC PZN (II)

¹ Ionizable compounds

triphenylmethyl halides

Ø Other initiators :

(C6H5)3CCl (C6H5)3C Cl+

Cl Cl+


ng(7)

tropylium halides

I2 + CH2 CR2 ICH2CIR2ICH2CR2 I

+ HIICH CR2

+ A + AM M

¹ Iodine

¹ Radical cations

radical cationmonomer

2. CATIONIC PZN (III)

MechanismF

AlCl3 + CH3Cl AlCl4CH3

CH CH

Initiation :Ø

AR + M ARM ARM n(n-1)M


ng(8)

CH2 C

CH3

CH3

+ CH3 AlCl4 CH3CH2 C

CH3

CH3

AlCl4

Propagation :Ø

CH3CH2 C

CH3

CH3

AlCl4 CH2 C

CH3

CH3

AlCl4CH2 C

CH3

CH3

CH3n M

2. CATIONIC PZN (IV)

Chain transfer :Ø

¹ Chain transfer to monomer

CH2C

CH3

CH3

+ CH2 C

CH3

CH3

AlCl4 CH2C

CH3

CH2

+ CH3 C

CH3

CH3

AlCl4

¹ Chain transfer to solvent

– H+


ng(9)

¹ Chain transfer to solvent

CH2C

CH3

CH3

AlCl4 + CH2 C

CH3

CH3

+

CH2C

CH3

CH3

+ CH3 C

CH3

CH3

AlCl4

– H+

2. CATIONIC PZN (V)

¹ Chain transfer to counterion

CH2C

CH3

CH3

AlCl4 CH2C

CH3

CH2

+ H AlCl4

Termination (self-termination):Ø

– H+


ng(10)

Termination (self-termination):Ø

CH2CH

Ph

OCCF3

O

CH2C

CH3

CH3

HOBCl3

CH2CHOCCF3

Ph

O

CH2CCl

CH3

CH3

+ BCl2OH

Feature of cationic PZN:¹ Fast initiation¹ Fast propagation ¹ Easy chain transfer ¹ Difficult to terminate

2. CATIONIC PZN (VI)

Not a living PZN

In 1985，Higashimura first reported the living cationic PZN


ng(11)

In 1985 Higashimura first reported the living cationic PZN of vinyl ether.

CH2 CH

OR

CH2 CH

OR

I I2δ δ

CH2 CH

OR

H n

CH3 CH

OR

I I2δ δ

CH3 CH

ORIHI I2

n CH2=CHOR

living polymer

In 1986，Kennedy reported the living cationic PZN of isobutylene.

R3COCCH3

O

+ BCl3 R3C OCCH3

O BCl3

CH3 CH3 O BCl3

2. CATIONIC PZN (VII)


ng(12)

R3C CH2C

CH3

CH2C

CH3 CH3

CH3

OCCH3

O BCl3δδ

n

n CH2=C(CH3)2

living polymer

Mw/Mn > 1.5 ~ 2.0

3. ANIONIC PZN (I)

InitiatorsFIn anionic vinyl PZN, the propagating chain is a carbanion; hence

initiation is brought about by species that undergo nucleophilic addition to monomer.

Nu + CH2 CHY NuCH2 CH

Yinitiator


ng(13)

Ø Organometallic compounds

initiator

RLi, NaNH2, RMgX, etc.

Ø Alkali metalsLi, Na, K insoluble in solvent low initiation efficiency

Na naphthalenesodium

3. ANIONIC PZN (II)

MechanismF

Initiation & Propagation :Ø

MtR + M MtR M MtRM n(n-1)M

R Li + CH CH R LiCH2 CH


ng(14)

R Li + CH2 CH

Y

R LiCH2 CH

Y

n MR LiCH2 CH

Y

CH2 CH

Y n

R LiCH2 CH

Y

Growth in one direction

3. ANIONIC PZN (III)

Na + Na

CH2 CH

Y

Na +

e– transfer

CH2 CH

Y


ng(15)

CH2 CH

Y

Na2 CH2 CH

Y

NaCH2CH

Y

Nacoupling

CH2 CH

Y

n

CH2 CH

Y

NaCH2CH

Y

Na

Growth in two direction

Termination : noØ

3. ANIONIC PZN (IV)

CH2 C

Y

Na

H

CH CH

Y

H Na+H

(several day or week)


ng(16)

¹ Termination by impurities : H2O, O2, CO2, etc.

¹ Termination by chain transfer agents after finishing PZN :

H2O, ROH, RCOOH, RNH2, etc.

3. ANIONIC PZN (V)

Feature of anionic PZN:

¹ Fast initiation¹ Slow propagation ¹ No chain transfer ¹ No termination

Living PZN

Living polymer :


ng(17)

Living polymer :polymers possessing still-active chain ends

100%Conv.%

MWM1

M2

KineticsF

3. ANIONIC PZN (VI)

In anionic PZNs, the rate of initiation is very high relative to that of propagation

][][][0 MIkR

dtMd

pp ==−

Integration of the rate expression


ng(18)

Integration of the rate expression tIk pMM 0][-

0 e][][ =

In anionic PZNs, the average kinetic chain length is simply equal to the number of monomer molecules reacted divided by the number

of chain initiated.

.(%)][][

][][][

0

0

0

0 convI

MI

MMv ×=−

=

Mol

ecul

ar w

eigh

t

(b)

(c)

3. ANIONIC PZN (VII)


ng(19)

0 20 40 60 80 100

Conversion %

Mol

ecul

ar w

eigh

t

(a)

(a) Step PZN; (b) Chain PZN; (c) Living PZN

3. ANIONIC PZN (VIII)

As monomer is completely consumed

0

0

][][

IMv =

Growth in one direction (RLi) : DP = v


ng(20)

DP = 2 vGrowth in two direction (Na/naphthalene):

nn

n

n

w

DPDPDP

DPDP 11

)1(1MWD

2+≈

++==

1.01 ~ 1.05

ApplicationsF

3. ANIONIC PZN (IX)

¹ Synthesize the polymers with narrow MWD.

ex., polystyrene from anionic PZN was used to GPC standard.

¹ Synthesize telechelic polymers.

OH O+


ng(21)

P Li P CH2CH2OH

P CH2 C

Ph

Ph

COOH

H3O+

CH2 C

Ph

Ph

P LiCO2/H3O+

3. ANIONIC PZN (X)

¹ Synthesize block copolymers.

CH2 CHn

C6H5

CH2CH CH2C

CH3

CH2C

CH3

C6H5

CH2CH CH2CH

n-1 C6H5

R CH2=CCO2CH3

CH3

m


ng(22)

CH2CH

n

CH2C

CO2CH3C6H5

CH2C

CO2CH3m-1

B

S(S)m-1(B)n(S)m-1S

NaB

couplingBB B(B)n -2B

(n-2) B

2m S

SBS triblock copolymer

3. ANIONIC PZN (XI)

P Li4 + SiCl4 Si

Star-block polymer

A major advantage of star-block copolymers is that they exhibit much lower melt viscosities, even at very high molecular weights,


ng(23)

much lower melt viscosities, even at very high molecular weights, than their linear counterparts.

H.W. :

Review exercises : 1. (a), (b); 2. (a), (b); 6. (a), (b), (c); 7

ANIONIC PZN (XI)

H.W. :

Review exercises : 1. (a), (b); 2. (a), (b); 6. (a), (b), (c); 7

7. What number average molecular weight polystyrene would be formed by polymerization of 2.0 M styrene with 1.0 × 10-3 M naphthalenesodium in


ng(24)

tetrahydrofuran? If the reaction were run at 25oC, how long would it take to reach 90% conversion? (Table 4.2)

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