Polymer Chemistry Controlled/Living Polymerization Donghui Zhang Fall 2012 1

1

Polymer Chemistry

Controlled/Living Polymerization

Donghui ZhangFall 2012

2

Architecture

3

Tacticity

• Asymmetric carbons have alternate configuration• Methylene hydrogens are racemic• Polymer stays in planar zig-zag conformation

R R R R R R R R

R R R R R R R R

R R R R R R R R

Isotactic

• All asymmetric carbons have same configuration • Methylene hydrogens are meso• Polymer forms helix to minimize substituent interaction

Syndiotactic

Atactic

• Asymmetric carbons have statistical variation of configuration

4

Statistical description of tacticity

5

Major Developments in the 1950-60's

Living Polymerization (Anionic)• Mw/Mn 1• Blocks, telechelics and stars available

(Controlled molecular architecture)• Statistical Stereochemical Control• Statistical Compositions and Sequences• Severe functional group restrictions

6

7

1.

2.

3.

4.

8

Good monomers for anionic polymerizations

. labile a-protonIn the polymers

steric stabilizing effect as well

9

Reactivity trend of monomers in anionic polymerizations

Increasing ease of initiation

10

Initiators for anionic polymerizations

11

12

Kinetics of Living Polymerizations

13

≈ 1+ 1/n

conversion (p)

conversion

conversion

14

1,4 trans content increases crystallinity, Tm > 25oC.1,4 cis content suppress crystallinity, low Tg (-110oC), Tm ~12oC; used for synthetic rubber

Solvent and Counter Ion Effect

15

Solvent characteristics

16

Solvent effect on anionic polymerizations

[M-]{M-n}

[M]propagating

Ke

kp

17

Solvent effect on anionic polymerizations

so is the stereoselectivity

18

End functionalization of anionic polymerizations

19

End functionalization of anionic polymerizations

20

Block copolymers from anionic polymerizations

21


22


23

Microphase separation of block copolymers

Sphere Cylinder Lamellar Gyroid

24

Application of block copolymers

Hillmyer, 2010 JACS

Russell, 2008 Nano Lett.

25

( )

Industry block copolymers (SBR)

26

Additional Developments in the 1980's

"Immortal" Polymerization (Cationic)– Mw/Mn 1.05– Blocks, telechelics, stars– (Controlled molecular architecture)– Statistical Compositions and Sequences– Severe functional group restrictions

27

Cationic Polymerization

28

Cationic Polymerization

29

Monomers for Cationic Polymerization

30

Kinetic Steps in Cationic Polymerization

:

of C+

31

32All these reactions kill the chain growth.

33

34

Industry Example of Cationic Polymerization

35

OR

+HI

OR

IZnI

OR

IOR

OR

ZnI

+

-

OR

I

ZnI

OR

dormantspecies

OR

IOR

ZnI

ORreactivespecies

(irriversible)

Strategy: prolong the life time of cationic propagating species by reversible formation of dormant species. (Note: anionic propagating species has a much longer life time).

36

37

38

Chain shuffling can increase PDI

39

Chain-End Functionalization of Aliphatic Polyether

40

Free Radical Initiated Polymerization

• Controlled Free Radical Polymerization• Broad range of monomers available• Accurate control of molecular weight• Mw/Mn 1.05 --Almost monodisperse• Blocks, telechelics, stars• (Controlled molecular architecture)• Statistical Compositions and Sequences

41

Free Radical Polymerizations

42

Iniferter approach

Otsu et al 1982

hn

recombination

exhibit living characteristics at low conversion, but PDI is broad as 3 can also initiate polymerizations.

43

The Key Concept in Living Radical Polymerization

formation of dormant propagating species reduces

the effective polymeric radical concentration and hence

minimize termination reactions

R is a capping agent ∙and does not initiate

chain growth

PDI= Mw/Mn=1+qM0/Mn = 1+q/n(Poisson distribution PDI = 1+1/n, slide 25)

(Page 144, Hiemenz and Lodge)

44

Stable Free Radical Polymerization (SFRP)or Nitroxide Mediated Polymerization (NMP)

+ radical initiator (BPO, AIBN)

N

O

SFRP Initiator System (e.g., biomolecular or unimolecular)

45

Stable Free Radical Polymerization (SFRP)Bimolecular Initiator System

46

Stable Free Radical Polymerization (SFRP)Unimolecular Initiator System

47

State of Art for SFRP

•MW > 105, PDI = 1.1-1.2•High reaction temperature (125-145oC)•Long reaction time (24-72 hr)•Low to moderate conversion (<70%)•Limited scope of monomers: St, MA, MMA etc. •functionalized alkoxyamine is required for block or telechelic polymer synthesis

lower temperature(60-80oC), shorter

reaction time (several hrs) and higher

conversion (>99%) are desired

48

49

Atom Transfer Reversible Polymerization (ATRP)

Basic components: vinyl monomers, metal catalyst/ligand and initiator

Example:

most common

50

Atom Transfer Reversible Polymerization (ATRP)

Keq’

R'

kp

ki

Keq

51

State of Art for ATRP

•MW > 105 easily, PDI = 1.1-1.6•reaction temperature (70-130oC)•Low to moderate conversion (<80%)•Tolerant of functional groups, wide scope of monomers: St, MA, MMA, acrylamide, vinylpyridine (VP), acrylonitrile (AN) etc. (acrylic acid, vinyl halide, vinyl ether, a-olefin cannot be polymerized) •Availability of a variety of initiator and catalysts. •block polymers and telechelic polymers are readily prepared.•metal contaminant is sometime less desired

52

Reversible Addition-Fragmentation Transfer Polymerization (RAFT)

SFRP (NMP) and ATRP involves reversible termination

RAFT involves reversible chain transfer

53

Reversible Addition-Fragmentation Transfer Polymerization (RAFT) Mechanism

Basic components: vinyl monomers, radical initiator and RAFT chain transfer agent.The number of growing chain is determined by both CTA and initiator content.

Stability can be

controlled by Z

group

54

RAFT Chain Transfer Agent

RAFT polymerizations are compatible with a variety of activated (St, MMA, MA etc.) or unactivated vinyl monomers (VAc, NVP). RAFT is versatile and robust as compared to SFRP and ATRP. But CTA agents need to be individually synthesized.

Design of CTA structures allows for control of the relative rate of addition and fragmentation steps

55

Ring Opening Metathesis Polymerization (ROMP)

[Ru] or [Mo] or [W]catalyst

2nd Gen. Grubb’s catalystSchrock’s catalyst

56


57


examples ofnorbornadiene

58


59


60

Synthesis of Conjugating Polymers from ROMP

ROMP

61


62

Ring Opening Polymerization (ROP)

metal-mediated reaction

organic-mediated reaction

Aliphatic Polyester synthesis

(Waymouth, Hedrick)

(Coates, Chisholm, Tolman/Hillmyer, Bourissou)

63

Polypeptide synthesis

Ring Opening Polymerization (ROP)

Polypeptoid synthesis

HN

O

nHN

O

O

O

R Initiators

initiators: RNH2 HNTMS2 (Cheng, 2007) Ni(bipy)(COD) (Deming, 1997)

-nCO2

NO

O

OR -nCO2

RNH2 N

O R

n

N

NN

O

O

O

R R

Rn-2

-nCO2

NHC NN

iPr

iPr iPr

iPrNHC

Zhang, 2010

64

Coordination Polymerization

• Stereochemical Control• Polydisperse products• Statistical Compositions and Sequences• Limited set of useful monomers, i.e. olefins

• SINGLE SITE CATALYSTS

Ziegler-Natta Polymerization (50-60’s)

65

Commodity Polyolefins

Polyethylene

Low Density (1939-1945)LDPE

Packaging Film, wire and cable coating, toys, flexible bottles, house wares, coatings

High Density (1954) HDPE

Bottles, drums, pipe, conduit, sheet, film

Linear Low Density (1975) Shirt bags, high strength films LLDE

66

Polyolefins• Polypropylene (PP, 1954)

• dishwasher safe plastic ware, carpet yarn, fibers and ropes, webbing, auto parts

67

Ziegler-Natta (Z-N) Polymerization

Radical polymerization is inefficient due to stable radicals from chain transfer

68

69

TiCl

Cl Cl

Cl

CH2 CH

CH3

CH2

CH2=CHCH3

Syndiotactic PP

isotactic PP

70

Consider polyethylene

radical process

Z-N process

% crystallinity: 40-60%

71

Single Site Catalyst 1990

Allows for production of elastomeric polypropylene (PP)

Waymouth 1995

atactic PP isotactic PPMAOMAO

72

Single Site Catalyst in 2000-olefinethylene

+

CTA

Allows for production of thermoplastic

elastomer

Arriola, Carnahan, Hustad, Kuhlman, Wenzel (Dow Chemical, Freeport, TX)

73

Acknowledgement•MIT OpenCourseWare: Synthesis of Polymers by Dr. Paula Hammondhttp://ocw.mit.edu/courses/chemical-engineering/10-569-synthesis-of-polymers-fall-2006/lecture-notes/•Note by USM Dr. Daniel Savin and Dr. Derek Pattonhttp://www.usm.edu/polymerkinetics/•Note by LSU Dr. Daly•Polymer Chemistry, 2nd edition, Hiemenz and Lodge•Principle of Polymerization, 4th edition, Odian•Polymer Chemistry, 4th edition, Pan, Zheijiang University

•“Functional Polymers via Anionic Polymerizations.” Akira Hirao, 1997 ACS Symposium Series.•“New Polymer Synthesis by Nitroxide Mediated Living Radical Polymerizations.” Craig Hawker, 2001, Chem. Rev. •“Atom Transfer Radical Polymerization.” Krzysztof Matyjaszewski, 2001, Chem. Rev.•“Copper(I)-Catalyzed Atom Transfer Radical Polymerization.” Krzysztof Matyjaszewski and Timothy Patten, 1999, Acc. Chem. Res.•“Toward Living Radical Polymerization.” Graeme Moad, Ezio Rizzardo, San Thang, 2008, Acc. Chem. Res.•“Living Radical Polymerization by the RAFT Process.” Graeme Moad, Ezio Rizzardo, San Thang, 2005, Aust. J. Chem.•“Living ring-opening metathesis polymerization catalyzed by well-characterized transition-metal alkylidene complexes.” Richard Schrock, 1990, Acc. Chem. Res.•“The Development of L2X2RuCHR Olefin Metathesis Catalysts: An Organometallic Success Story.” Robert Grubbs, 2001, Acc. Chem. Soc.•“Organocatalytic Ring-Opening Polymerization.” Robert Waymouth, James Hedrick, 2007, Chem. Rev.•“Controlled Ring-Opening Polymerization of Lactide and Glycolide.” Didier Bourissou, 2004, Chem. Rev.•“Synthesis of Well-Defined Polypeptide-Based Materials via the Ring-Opening Polymerization of α-Amino Acid N-Carboxyanhydrides.” Nikos Hadjichristidis, 2009, Chem. Rev.

http://ocw.mit.edu/courses/chemical-engineering/10-569-synthesis-of-polymers-fall-2006/lecture-notes/

http://www.usm.edu/polymerkinetics/

Documents

Polymer Chemistry Controlled/Living Polymerization Donghui Zhang Fall 2012 1