1. Polymer Chemistry Controlled/Living Polymerization
Donghui Zhang
Fall 2012

2. Architecture

3. Tacticity Isotactic Syndiotactic Atactic
All asymmetric carbons have same configuration
Methylene hydrogens are meso
Polymer forms helix to minimize substituent interaction
Syndiotactic
Asymmetric carbons have alternate configuration
Methylene hydrogens are racemic
Polymer stays in planar zig-zag conformation
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

7. 1. 2. 3. 4.

8. . Good monomers for anionic polymerizations labile a-proton
In the polymers
steric stabilizing effect as well

9. Reactivity trend of monomers in anionic polymerizations
Increasing ease of initiation

10. Initiators for anionic polymerizations

12. Kinetics of Living Polymerizations

13. conversion
≈ 1+ 1/n
conversion
conversion (p)

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

15. Solvent characteristics

16. Solvent effect on anionic polymerizationsKe
[M]
propagating kp
{M-n}
[M-]

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. Block copolymers from anionic polymerizations

22. Block copolymers from anionic polymerizations

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+

32. All these reactions kill the chain growth.

34. Industry Example of Cationic Polymerization

35. (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).

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  Almost monodisperse
Blocks, telechelics, stars
(Controlled molecular architecture)
Statistical Compositions and Sequences

41. Free Radical Polymerizations

42. Otsu et al 1982 Iniferter approachhn
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
PDI= Mw/Mn=1+qM0/Mn = 1+q/n
(Poisson distribution PDI = 1+1/n, slide 25)
(Page 144, Hiemenz and Lodge)
R∙ is a capping agent and does not initiate chain growth
formation of dormant propagating species reduces the effective polymeric radical concentration and hence minimize termination reactions

44. Stable Free Radical Polymerization (SFRP)
or Nitroxide Mediated Polymerization (NMP)
SFRP Initiator System (e.g., biomolecular or unimolecular)
+ radical initiator (BPO, AIBN)

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 ( oC)
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

49. Atom Transfer Reversible Polymerization (ATRP)
most common
Example:
Basic components: vinyl monomers, metal catalyst/ligand and initiator

50. Atom Transfer Reversible Polymerization (ATRP)kp ki
Keq
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. Stability can be controlled by Z group
Reversible Addition-Fragmentation Transfer Polymerization (RAFT) Mechanism
Stability can be controlled by Z group
Basic components: vinyl monomers, radical initiator and RAFT chain transfer agent.
The number of growing chain is determined by both CTA and initiator content.

54. RAFT Chain Transfer Agent
Design of CTA structures allows for control of the relative rate of addition and fragmentation steps
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.

55. Ring Opening Metathesis Polymerization (ROMP)
[Ru] or [Mo] or [W]
catalyst
Schrock’s catalyst
2nd Gen. Grubb’s catalyst

56. Ring Opening Metathesis Polymerization (ROMP)

57. Ring Opening Metathesis Polymerization (ROMP)
examples of
norbornadiene

58. Ring Opening Metathesis Polymerization (ROMP)

59. Ring Opening Metathesis Polymerization (ROMP)

60. Synthesis of Conjugating Polymers from ROMP

61. Ring Opening Metathesis Polymerization (ROMP)

62. Ring Opening Polymerization (ROP)
Aliphatic Polyester synthesis
metal-mediated reaction
(Coates, Chisholm, Tolman/Hillmyer, Bourissou)
organic-mediated reaction
(Waymouth, Hedrick)

63. Ring Opening Polymerization (ROP)
Polypeptide synthesis
Polypeptoid synthesis

64. Coordination Polymerization
Ziegler-Natta Polymerization (50-60’s)
Stereochemical Control
Polydisperse products
Statistical Compositions and Sequences
Limited set of useful monomers, i.e. olefins
SINGLE SITE CATALYSTS

65. Commodity Polyolefins
Polyethylene
High Density (1954)
HDPE
Bottles, drums, pipe, conduit, sheet, film
Low Density ( )
LDPE
Packaging Film, wire and cable coating, toys, flexible bottles, house wares, coatings
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

69. isotactic PP
Syndiotactic PP

70. Consider polyethylene
% crystallinity: 40-60%
radical process
Z-N process

71. Single Site Catalyst 1990 Waymouth 1995
MAO
MAO
atactic PP
isotactic PP
Waymouth 1995
Allows for production of elastomeric polypropylene (PP)

72. Allows for production of thermoplastic elastomer
Single Site Catalyst in 2000
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 Hammond
Note by USM Dr. Daniel Savin and Dr. Derek Patton
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.