Anionic Synthesis of Liquid Polydienes and Their Applications

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 • Microstructure • Macrostructure • Applications

3. Liquid polydiene • Low molecular weight homopolymers or copolymers containing unsaturated carbon-carbon double bonds • Curing by sulfur or peroxides

4. Why anionic polymerization? • 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)

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

7. Microstructure of polydienes * amorphous

8. Counter ion and initiator concentration effect Lithium catalyst • soluble in hydrocarbon solvents • the lowest 1,2-vinyl content • good low temperature properties * 1,2-vinyl for polybutadiene

9. aggregated Contact ion pair Free ions Polar additive and Temperature effect • Polar solvent • Presence of Lewis base (alkali metal alkoxides) in HC solvent • Monodendate vs. Bidendate • Temperature • Polybutadiene with the highest 1,2-vinyl can be prepared in polar solvent at lower reaction temperature

10. Effect of styrene content on 1,2-vinyl formation in styrene-butadiene copolymerization Comonomer effect (random copolymerization) • Adding polar additives • Maintaining the concentration of comonomer with a lower monomer • reactivity ratio high during the 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 (Eacyclization>Ea propagation)

13. Cyclization of polybutadiene • 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 • Not applicable for functionalized polymer • Cost reduction of liquid polymer production • Eachain transfer > Eapropagation • thermodynamic control • kinetic control

16. 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 • 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 (Eachain 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. DVB core * * * * + * * * * * * * = reactive chain end Branched polymers by linking reactions • Chlorosilane SiCl4 + 4 PLi SiP4 + 4LiCl • Divinylbenzene • Epoxy and silanol compounds P-OH PLi + 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. Properties that depend on chain ends Molecular weight Molecular weight Molecular weight effect Properties that depend on entanglement

24. High MW Log ha h0=KMwP Shear thinning P=3.4 0 1 2 3 . P=1 Log shear rate () Mcr Newtonian Region Broad MWD Low MW Oriented coils Random coils Viscosity • Macrostructural (MW) effect J. T. Gruver and G. Kraus, J. Polym. Sci. Part A, 2, 797 (1964) 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. Microstructure (1,2- vs. 1,4) Macrostructure Sulfur crosslinking 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. 5 phr coagent HVPB-MA LVPB-MA Adhesion Potential - Metal EPDM, Peroxide cure • PB-MA adhesion promoters increase adhesive bond strength

36. PU hard domains elastomeric soft segment T < Tsoftening T > Tsoftening Vulcanizate Melt Flow Thermoplastic polyurethanes HTPB / Diisocyanate / Diol chain extender • 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. + Polymer Layered clay Intercalated nanocomposite Exfoliated nanocomposite Nanocomposite • Mechanical and thermal properties • Permeability • Flame retardance • UV resistance 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