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Polymer Chemistry

Guangxi University School of Chemistry & Chemical Engineerin

g

Li Guang Hua (李光华)

Lab：材料楼—409#，321# E-mail : lighua@gmail.comCell phone: 15978133590

CHAPTER 6

1. Introduction

Reactions of Vinyl Polymers :

2. Functional Group Reactions

3. Ring-Forming Reactions

4. Crosslinking

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4. Crosslinking

5. Block and Graft Copolymer Formation

6. Polymer Degradation

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1. INTRODUCTION (I)

Monomer PZN Polymer 1

Polymer 2

Chemical reaction

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Polymer 2

Synthesize new polymers.

Endow new functionality to polymers.Chemical reaction

1. INTRODUCTION (II)

¹ Introduce cyclic unites into polymer backbone.

¹ Introduction or modification of functional groups.

Chemical modifications of vinyl polymers are grouped into five general categories:

Ø

DP unchanged

DP unchanged

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¹ Reactions leading to block and graft copolymers

¹ Crosslinking reactions

¹ Degradation reactions

DP unchanged

DP

DP

DP

1. INTRODUCTION (III)

Influence factors of polymer reactions :Ø

¹ Physical factors

¤ Crystallinity (%) of polymer

¤ Solubility of polymer

¤ Structure of polymer chain

Crystalline regionsAmorphous regions

Crosslinking or steric effects

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¹ Chemical factors

¤ Probability effect

CH2

CH

CH2

CH

CH2

CH

CH2

CH

CH2

CH

Cl Cl Cl Cl Cl

CH2

CH

CH2

CH

CH2

CH

CH2

CH

CH2

CH

Cl

Zn

1. INTRODUCTION (IV)

¤ Neighboring group effect

CH2C CH2CH

CH3

C CO O

O O

CH2C

CO

C

CHC

O O

H2CH3

+

O

NO2

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NO2

CH2C CH2CH

CH3

CO2 CO2

OH–

2. FUNCTIONAL GROUP REACTIONS (I)

Introduction of New Functional GroupsF

CH2CH2 n CHCH2

Cl n

Cl2

chlorination

Chlorinated PE (CPE)

á Increase flame resistance and solubility compared with PE

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CH2CH

SO2Cl n

CH2CH2 nCl2, SO2

chlorosulfonation

á Provide sites for subsequent crosslinking reaction

2. FUNCTIONAL GROUP REACTIONS (II)

CH2CH

C6H5 n

CF2CF

C6F11 n

F2

fluorination

á Enhance chemical inertness and improve solvent barrier

CH OCH Cl

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CH2CH

n

CH2CH

CH2Cl n

CH3OCH2ClAlCl3

Benzene ring : nitration, sulfonation, chloromethylation, etc.

2. FUNCTIONAL GROUP REACTIONS (III)

Conversion of Functional GroupsFSome polymers :

difficult or impossible to prepare by direct PZN

CH2CH

OCCH

CH2CH + CH3COOCH3CH3OH/KOH

Δ

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OCCH3

O n

OH nΔ

CH2 CH

OCOCH3

n

R· PZN

CH2 CH

OH

CH3CHOtautomer

×

Poly(vinyl alcohol) (PVA)

2. FUNCTIONAL GROUP REACTIONS (IV)

CH2C

CH3

C O

OSi(CH3)3 n

CH2C

CH3

CO2H n

1) H2O, OH–

2) H+

Isotactic or syndiotacticIsotactic or syndiotactic

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CH2 C

C O

OSi(CH3)3

CH3

n

R– PZN

CH2 C

COOH

CH3

× R· PZN

3. RING-FORMING REACTIONS (I)

Introduction of cyclic units into polymers :¹ Rigidity¹ Glass transition temperature (Tg)

¹ Thermal stability

EX.,

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Carbon fiberØ

Rayon fiberpyrolysis Carbon fiber (1870s by Edison)

1000~2000oC

PAN fiberpyrolysis

1000~2000oC

graphitization2500~2800oC

Graphite fiber(Carbon fiber)

C% : 85 ~ 99% (high strength)

C% > 99% (high modulus)

3. RING-FORMING REACTIONS (II)

C C CN NN N N N

Δ

Δ

Ladder –HCN

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N N N

H H H

Ladder graphite-type

polymer–HCN–N2

á High strength, high modulus, high thermal stability

Widely used in high performance composites

3. RING-FORMING REACTIONS (III)

4000 K Carbon nanotubeCarbon-arc furnace

á The nanotubes are much stronger than conventional graphite fibers, and hold promise of yielding composites with superior properties.

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diamond C60 (1985)

graphite (10, 10) tube (1991)

3. RING-FORMING REACTIONS (IV)

CH2CH

OH

CH2CH

OH

CH2CH

OH

OO

CH2

OHHCHO

H+

poly(vinyl formal)

“vinylon” (维尼龙)

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OH OHOH

OO

CH2

C3H7

OHC3H7CHO

H+

poly(vinyl butyral)

á Used as a plastic film in laminated safety glass

PVA

4. CROSSLINKING (I)

¹ Vulcanization (硫化，交联)

For the commercial standpoint, crosslinking is fundamental to the rubber and elastomer industries.

A general term applied to the crosslinking of polymers, particularly elastomers

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¹ Radiation crosslinking

¹ Photochemical crosslinking

¹ Crosslinking through labile functional groups

¹ Ionic crosslinking

Use peroxides, sulfur

VulcanizationF

4. CROSSLINKING (II)

CH2CH2RO +

CHCH2

CHCH2

+

CHCH2 + ROH

CHCH2

CHCH2

Ø

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CH2CH RO+CHCH2 + ROHCHCH CHCH2

CHCH CHCH2

CHCH CHCH2

+CHCH CHCH2

CHCH CHCH2

Ø

4. CROSSLINKING (III)

CHCH CHCH2

+CH2CH CHCH2

CHCH CHCH2CHCH CHCH2 +

CHCH CHCH2

CH2CH CHCH2

CH2CH CHCH2

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CH2CH CH2CH2

CHCH CHCH2 +

S8

CH2CH CHCH2

Sm

+ SnCH2CH CHCH2 + Sm Sn

δ δØ

4. CROSSLINKING (IV)

CH2CH CHCH2

CH2CH CHCH2

Sm

CH2CH CH2CH2

Sm

+ CHCH CHCH2S8

Sm

CHCH CHCH2

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CH2CH CHCH2

CHCH CHCH2

CH2CH CHCH2

SmCH2CH CHCH2

CHCH CHCH2

CH2CH CH2CH2

Sm

+

CHCH CHCH2

4. CROSSLINKING (V)

The rate of vulcanization with sulfur is slow.

¤ Accelerator :

[(CH3)2NCS ]2Zn2+

S S S

(CH3)2NCSSCN(CH3)2

Zinc dithiocarbamate tetramethylthiuram disulfide

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¤ Activator :

Zinc oxide; Stearic acid

二硫代氨基甲酸盐

4. CROSSLINKING (VI)

Radiation crosslinkingFRadiation : photons, electrons, neutrons, or protons

Crosslinking & degradation

¹ The doses of radiationHigh doses of radiation Degradation

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¹ Polymer structure (low doses of radiation)

¤ 1,1-disubstituted vinyl polymers Degradation

¤ Helogen-substituted vinyl polymers Loss of helogen

¤Most other vinyl polymers Crosslinking

CH2CH2

CH2CH2 + H(neighboring chain)

4. CROSSLINKING (VII)

+ HCHCH2radiation

+ H2CHCH2

For LDPE

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CHCH2

CHCH2

+CHCH2

CHCH2

CH2CH

R

CHCH

R

+ H CH CH + RH

4. CROSSLINKING (VIII)

Photochemical crosslinking (photocrosslinking)FUltraviolet or visible light-induced crosslinking

Ø Applications :

¹ Printed circuits for electronic equipment

¹ Printing inks

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¹ Printing inks¹ Coatings for optical fibers¹ Varnishes for paper and carbon board (复写纸)

¹ Finishes for vinyl flooring, wood, paper and metal

¹ Curing of dental materials

Surface treatment

Two basic methods of photocrosslinkingØ

¹ Incorporating photosensitizers into polymer

4. CROSSLINKING (IX)

C

O

benzophenone

hvC

O *

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benzophenoneCH2CH

R

C

OH

+CH2C

R

combination

Crosslinked polymer

4. CROSSLINKING (X)

CH2CHCH2CH

C O

R

C O

R

CH2CH2

C O

R

C OR

CH2 C+

CH2CHCH2CH2

C O RCO

+

hv

chromophore

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C O

RRC+

Crosslinked polymer

chromophore

4. CROSSLINKING (XI)

¹ Photocycloaddition

CH CHArOC

O

CHArCH CO

O

+OC

O

CO

O

Ar

Ar

hv

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+ hv

[2π+ 2π] cycloaddition

[4π+ 4π] cycloaddition

Crosslinking through labile functional groupsF

4. CROSSLINKING (XII)

CH SO2Cl2

CH

CH2

SO2NH

CH2

CHAr NHSO2H2N NH2Ar

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CH22

CH

CH2

SO2OROSO2

CH2

CHHO OHR

Ionic crosslinkingF

4. CROSSLINKING (XIII)

CH2CH

SO2Cl

CH2CH

SO2

CHCH2

O2SPb2+

PbO, H2O

polyelectrolyte

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CH2CH2

CH3

CO2H

CH2Cxy

ionomoer

Ca(OH)2CH2CH2

CH3

CO2

CH2Cxy

CH2CH2

CH3

CO2

CH2Cxy

Ca 2+Physical crosslinking

5. BLOCK & GRAFT COPOLYMER (I)

F Block copolymers

A B

Solution Solid State

Unique phase behavior

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Spheres gyroid lamellae cylinder(BCC) (hex)c ≥ cmc (Micelle)

volume fraction (f) of B block ↑

H2O 10 ~ 50 nm

Thermoplastic elastomers, plastic modifiers, adhesives,membranes, polymer blends, DDS, nanocomposites, etc.

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5. BLOCK & GRAFT COPOLYMER (I)

LiPSO

OCH3 PS-b-PMMA Li+ n-BuLiTHF-78oC

CH3OH

PS-b-PMMA

By anionic PZNØ

PS-b-PMMA

PIB PIB-b-PS+ coinitiator TiCl4

-80oC 2. CH3OH

1.

By cationic PZNØ

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By living radical PZNØ

5. BLOCK & GRAFT COPOLYMER (II)

CH3O

O

CH

CH3

BrC CH3O

O

CH

CH3

C CH2 C

CH3

C O

OCH3

Br

n

MMACuCl/bpy

PMMA macroinitiator

CH3O

O

CH

CH3

C CH2 C

CH3

C O

OCH3

Br

n

CH2 CH

C O

OCH3 m

MACuCl/bpy

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N C

CH3

CH3

CO

NH CH2 CH2 O

Cl

O2

Azo-alkyl halide

5. BLOCK & GRAFT COPOLYMER (III)

By difunctional initiatorsØ

Azo-alkyl halide

The othersØ

CHCH2OH

Ph

+ OCN CHCH2

Ph

OCNH

O

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5. BLOCK & GRAFT COPOLYMER (IV)

CH3

CH3

CHCH2OC

R CHCH3

CH3

CH3

CH3

CHCH2OC

R CCH3

CH3

OOH

O2

MΔ

CH3

CH3

CHCH2OC

R CCH3

CH3

O

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Graft copolymers F

5. BLOCK & GRAFT COPOLYMER (V)

Grafting fromØ

X

X

X

X

XnM

X = initiating group

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O

CH2CH

OCCH3

O

CH2CH

OCCH2(CH2CH2)x

O

CH2C

OCCH3

(CH2CH2)yCH2=CH2

peroxide

X = initiating group

CH2CH CH2CH

Ph

BF3OH+

OCH3

Grafting ontoØ

5. BLOCK & GRAFT COPOLYMER (VI)

CH2CH

OCH3

CH2CH

Ph

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O

N+ HO2C CNHCH2CH2OC

O O

Grafting throughØ

5. BLOCK & GRAFT COPOLYMER (VII)

+M Initiator

macromer ormacromonomer

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macromonomer

6. POLYMER DEGRADATION (I)

Degradation :Reduction of molecular weight

The mode of degradation¹ Depropagation or depolymerzation¹ Random chain scission¹ Elimination of side groups

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¹ Elimination of side groups

The methods of degrading polymers¹ Chemical degradation (chemical reagents: O2, H2O, etc.)¹ Thermal degradation (heat)¹ Radiation degradation (photons, protons, electrons, neutrons )¹ Ultrasonic or mechanical degradation¹ Microbiological degradation (microbe)

6. POLYMER DEGRADATION (II)

Chemical degradationFOxidationØ

CH2CHCH2CCH2CH

R RR

OOHCH2CHCH2

R RR

O+ CCH2CH + OH

Saturated polymer

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Saturated polymer

CH2 CH CH CH2O2 CH2 CH CH CH

OOH

CH2 CH CH CH2

O

+ OH

degradation & crosslinking

Unsaturated polymer

6. POLYMER DEGRADATION (III)

CH2 CH CH CH2O2

Unsaturated polymerCH2 CH CH CH2

O O

CH2 CH CH CH2

O O

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CH2CH O2

á Order of resistance to oxidation

CH2 C

CH3

CH3

n

CH2 CH2 n CH2 CH

CH3 n

CH2 CH CH CH2 n> > >

6. POLYMER DEGRADATION (IV)

Thermal degradationF

á The order of thermal stability of polyolefins

CH2 C

CH3

CH2 CH2 n CH2 CH> >

For C-C main chain

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CH2 C

CH3 n

CH2 CH2 n CH2 CH

CH3 n

> >

For C-H bond

CH3 CH2 CH C C CH2> > >

6. POLYMER DEGRADATION (V)

Thermal degradationF

O

CH2CH

OCCH3

n CH CH +

O

HOCCH3nΔ

¹ Elimination of side groups

PVAc

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PVAc

¹ Random chain scission

CH2CH2CH2CH2 CH2CH2 + CH2CH2

CH CH2 + CH3CH2

6. POLYMER DEGRADATION (VI)

¹ Depropagation or depolymerzation

CH2CCH2C

R

R

R

R

CH2C

R

+

R

CH2 CR

R

1,1-disubstituted polymer :

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PMMA

Poly(α-methyl styrene)

6. POLYMER DEGRADATION (VII)

Radiation degradationFRadiation : photons, electrons, neutrons, or protons

Crosslinking & degradation

CH2CCH2C

R RUVΔ

depolymerization

Ø

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CH2CCH2C

R RΔ

depolymerization

CH2CCH2C

R

R

R

RUVR.T.

Crosslinking & degradation

1,1-disubstituted polymer

POLYMER DEGRADATION (VIII)

Photodegrable plastics

Other vinyl polymers UV crosslinking

All vinyl polymers High dosage of radiation degradation

Ø

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COR

O

UVC

OR

+

O

+UV

H.W. : 1, 2, 4; 7, 10

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