1. Anionic Synthesis of Liquid Polydienes and Their Applications
Taejun Yoo* and Steven Henning
October 14, 2009

2. Contents Anionic synthesis of liquid polydienes
Microstructure
Macrostructure
Functionalization
Structure and properties
Applications

3. Additives for rubber products
Liquid polydiene
Low molecular weight homopolymers or copolymers containing unsaturated carbon-carbon double bonds
Curing by sulfur or peroxides
Liquid polydiene
Elastomer
Molecular weight
1,000-10,000
100,000-1,000,000
Physical state
Viscous liquid
Solid
Processing
Low shear
High shear
Polymerization type
Batch or semi batch
Batch or continuous
Modification
Easy
Relatively harder
Catalyst cost on product
Critical
Negligible
Application
Additives for rubber products
Main rubber products

4. Why anionic polymerization? A variety of different liquid polymers !
Microstructure
Polymer composition (styrene, butadiene, isoprene)
Mode of addition (1,4- and 1,2- vinyl or 3,4-vinyl)
Monomer sequence distribution (random, tapered or block)
Cyclic structure (batch vs. semi batch)
Macrostructure
Molecular weight and distribution
Molecular geometry (linear and branched)
Functionalization
In chain
Chain end: mono and difunctional (telechelic)
A variety of different liquid polymers !

5. Commercial liquid polydienes (anionic)
Plastikator 32
Butarez (HTPB and CTPB)
Producer
Liquid polymer
Trade name MW
1,2-vinyl
(%)
Functional group
Post polymerization Modification
Nippon Soda PB
Nisso
1k-4k
85-90
OH, COOH
Maleinization
Hydrogenation
Sartomer
PB, SBR
Ricon
Krasol
1.5k-8k
2k-10k
20-90
60-65 OH
Epoxidation
Synthomer
Lithene
1k-9k
10-55
Kuraray
PB, PI
SBR, SIR
LBR
LIR
25-50k -

6. Microstructure Mode of addition (1,4- vs. 1,2-) Cyclic vinyl formation
Reaction conditions
Comonomer effect in copolymerization
Cyclic vinyl formation

7. Microstructure of polydienes
Tg (°C)
Tm (°C)
Cis 1,4-
- 107 2
Trans 1,4-
-106
97/145
Isotactic 1,2
-15
128
Syndiotactic 1,2
-28
156
1,2-vinyl* -4 -
* amorphous

8. Counter ion and initiator concentration effect
Lithium catalyst
soluble in hydrocarbon solvents
the lowest 1,2-vinyl content
good low temperature properties
Catalyst
Cis-1,4
Trans-1,4
1,2
Lithium 35 52 13
Sodium 10 25 65
Potassium 15 40 45
Rubidium 7 31 62
Cesium 6 59
Initiator Concentration (M)
1.4-Cis (%)
1,4-Trans (%)
3,4-Vinyl (%)* PI
6.12x10-2 74 18 8
1.0x10-3 78 17 5
1.0x10-4 84 11
0.8x10-5 97 3 PB
5x10-1 53 47
5x10-2 90 10
5x10-3 93 7
* 1,2-vinyl for polybutadiene

9. Polar additive and Temperature effect
Free ions
aggregated
Contact ion pair
Polar solvent
Presence of Lewis base (alkali metal alkoxides) in HC solvent
Monodendate vs. Bidendate
Temperature
T.A. Antkowiak, A.E. Oberster, A.F. Halasa, and D.P. Tate JPS, Part A-1 Vol. 10, 1319 (1972)
Polybutadiene with the highest 1,2-vinyl can be prepared in polar solvent at lower reaction temperature

10. Comonomer effect (random copolymerization)
Adding polar additives
Maintaining the concentration of comonomer with a lower monomer
reactivity ratio high during the copolymerization.
Effect of styrene content on 1,2-vinyl formation in styrene-butadiene copolymerization
The presence of styrene in copolymerization results in less 1,2-vinyl content than BD homopolymerization due to steric effect between allylic chain end and styrene unit.

11. Cyclization of polybutadiene
High 1,2-vinyl
Lewis base
Reaction temperature
Monomer starving condition
Batch vs. Continuous
Monomer feed rate
G. Quack and L. J. Fetters, Macromolecules, 11, 369 (1978).
Cyclization is favorable in monomer starved reaction condition
Cyclization consumes 1,2-vinyl

12. Cyclization of polybutadiene (continuous system)
Cyclization reaction increases as
polar additive amount increases (higher 1,2-vinyl)
reaction temperature increases (Ea cyclization>Ea propagation)

13. Cyclization of polybutadiene
Total 1,2-vinyl
Cyclic vinyl 76 18 26 77 29
Stiff structure increases Tg
Logh ~ (T-Tg)-1
Cyclic vinyl has more impact on the physical properties than 1,2-vinyl

14. Macrostructure Molecular weight (gram of monomer/moles of initiator)
Molecular weight distribution (Ki >Kp, Xw/Xn=1+1/Xn)
Branched structure (linking reaction and transmetallation)

15. Chain transfer reaction
Ea chain transfer > Ea propagation
thermodynamic control
kinetic control
Not applicable for functionalized polymer
Cost reduction of liquid polymer production

16. Chain transfer reaction
Mn calculated: 6,830
Mn measured : 6,120 PI: 1.57
Mn calculated: 17,750
Mn measured : 1,830 PI: 3.54
Chain transfer reaction in lithium initiated anionic polymerization increases as
size of counter ion increases (Li < Na <K )
polar additive amount increases (Li)
reaction temperature increases (Ea chain transfer >Ea propagation)
monomer feed rate decreases
and
chain transfer reaction is maximized in pure toluene

17. Branched polymer [h]b < [h]l
# of branch
Length of branch
MW of backbone
Type of branch (star, graft and hyper branched)
Reduction in melt and solution viscosities
Processing benefits, applications

18. Branched polymers by linking reactions
Chlorosilane
SiCl4 + 4 PLi SiP4 + 4LiCl
Divinylbenzene
DVB core * *
* = reactive chain end +
Epoxy and silanol compounds
PLi +
P-OH OH OH OH OH OH OH OH
Quirk and Zhou US patent 7,235,615

19. Functionalization Chain end functionalization
Post polymerization modification
(Functional groups are randomly distributed on polymer backbone)

20. Chain end functionalization
Functional agent
Protected functional initiator or agent
a- or w-functionalized polymer by deprotection
Difunctional initiator
(HTPB)
(CTPB)

21. Post polymerization modification
Hydrogenation (thermal stability and copolymer)
Epoxidation
Maleinization
1,2 > 1,4
1,4 > 1,2
1,4 > 1,2
Esterification
Addition of acryl group
Imidization

22. Structure-Property Relationships

23. Molecular weight effect
Properties that depend on chain ends
Properties that depend on entanglement
Entanglement
Intermolecular interaction Number of end groups Mw Mn
Melt viscosity
h=KMwa
Izod impact resistance
Tensile strength
Flexural modulus
Tg and Tm

24. J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964)
Viscosity
Macrostructural (MW) effect
Mcr
h0=KMwP
P=1
P=3.4
Newtonian Region
Low MW
High MW
Log shear rate ()
Log ha 1 2 3 .
Broad MWD
Shear thinning
J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964)
Random coils
Oriented coils
Mcr
Polybutadiene: 6,000
Polyisoprene: 10,000

25. Viscosity Microstructural effect
Zero shear viscosity data (Brookfield) as a function of both molecular weight and microstructure using a series of commercially available liquid polydiene grades ( low vinyl polybutadiene,  high vinyl polybutadiene,  poly(butadiene-co-styrene).
Viscosity of liquid polydiene is dependant on MW as well as microstructure:
high vinyl polybutadienes > SBR copolymers > low vinyl polybutadienes

26. Viscosity
Functional group effect on chain end functionalized PB

27. Glass transition temperature
Tg = Tg() - (A/Mn)
Tg as a function of vinyl content and molecular weight for a series of commercially available liquid polybutadienes.
Tg as a function of comonomer content for a series of butadiene-isoprene copolymers.

28. Glass transition temperature
Functional group effect
Tg as a function of oxiran content for a series epoxidized liquid polybutadienes.

29. Molecular weight dependency of crosslinking rate of polyisoprene
Microstructure (1,2- vs. 1,4)
Macrostructure
Sulfur crosslinking
Molecular weight dependency of crosslinking rate of polyisoprene
Mc of diene elastomers: ~ 12,000 g/mol
Liquid polydienes do not form elastically effective crosslinks
Mizuho Maeda, RubberChem 2006

30. Applications Functional additives Low viscosity (processing)
Similar chemical properties of elastomers (vulcanization)
Outstanding properties (High thermal stability, good moisture and chemical resistance, good adhesive characteristics and excellent electrical properties)

31. Unfunctionalized liquid polydienes
Processing aids
Low viscosity, non-toxic, low volatility and no bleeding (miscible with rubbers and non-
extractable)
Coagents
1,2-polybutadiene for peroxide cure of elastomers
Wire and cable applications (better heat aging, fluid resistance and electrical properties)
Engineering rubber products (belts, hoses, gaskets and rollers)
Coating and potting agents
Autoxidation with baking or metallic driers (high level of unsaturation)
Tire application
HVPB and SBR: wet traction
LVPB: wear, low temperature properties

32. Functionalized liquid polydienes
Propellant binder: HTPB and CTPB
Adhesion promoters: Maleinized PB
Polyurethanes: HTPB
Epoxy resin modification: HTPB and CTPB
UV curing: Deoxidized, acrylated PB
Nanocomposite
Polymer-filler interaction

33. Summary
The microstructure and macrostructure affect the Tg and bulk viscosity of final diene resin products.
Lithium-based anionic polymerization provides liquid polydienes with a variety of microstructure and macrostructure including functionalization.
The unique characteristics of liquid polydiene products has led to their utility in a wide variety of markets and applications such as functional additives for rubber and other thermosets, modification of thermoplastics, adhesives, and coatings.

35. Adhesion Potential - Metal
5 phr coagent
LVPB-MA
HVPB-MA
EPDM, Peroxide cure
PB-MA adhesion promoters increase adhesive bond strength

36. Thermoplastic polyurethanes
HTPB / Diisocyanate / Diol chain extender
PU hard
domains
elastomeric
soft segment
Melt Flow
T < Tsoftening
T > Tsoftening
Vulcanizate
Adhering a Urethane component to a Rubber Compound substrate
Diene-segments interpenetrate and co-cure with rubber compound
Urethane segments bond to similar structure in PU
Functional Additive to a traditional Rubber Compound
varied loading increases impact on physical properties
impart modulus while minimizing hysteresis (vs. TPE)
realize advantages from phase structure at higher loading

37. Intercalated nanocomposite Exfoliated nanocomposite
Polymer
Layered clay +
Intercalated nanocomposite
Exfoliated nanocomposite
An organophilic clay can be produced from a normally hydrophilic clay by ion exchange with an organic cation such as an alkylammonium ion. For example, in montmorillonite, the sodium ions in the clay can be exchanged for an amino acid such as 12-aminododecanoic acid (ADA):
Na+-CLAY + HO2C-R-NH3+Cl- .HO2C-R-NH3+-CLAY + NaCl
Mechanical and thermal properties
Permeability
Flame retardance
UV resistance