Ultra high cis Polybutadiene by Monomeric Neodymium Catalyst and its Tensile and Dynamic properties

Ultra high cis polybutadiene, containing over 97% cis content, is of particular interest in the rubber industry because of its high physical properties for tire, golf-ball and high impact polystyrene (HIPS) applications. A new neodymium catalyst, Nd(neodecanoate)3 (neodecanoic acid) (NdV4), designed for active catalyst in solution polymerization to satisfy the very requisite of anhydrous and dissociate structure with high solubility, was employed to prepare ultra high cis polybutadiene. The Ndcatalyst composed of Nd (neodecanoate)3 (neodecanoic acid) / A1Et2C1/Al (iBu)3 showed a high activity (2.0 X 106g/Nd mol h) and produced polybutadiene with over 97% cis content. The dissociate active-site composed of monomeric compound NdV4, Al (iBu)3 and A1Et2C1 was proposed through density functional calculations (B3LYP/CEP-31G). The optimum structure shows that the eta3-allyl ligand of the chain end is coordinated to Nd (III), and Nd, 01, C1, and C4 atoms are on the same plane. The bond distances are Nd-C1 2.591 A, Nd-C2 2.740 A, Nd-C3 2.807 A, Nd-eta2-(C6-C7) 3.037 A, Nd-C12.650 A, Nd-01 2.172 A, C1-C2 1.452 A, and C2-C3 1.411 A, respectively. The microstructure of polybutadiene was controlled by chaintransfer with NdV4, catalyst composition and phosphine compounds. As with increase of Nd concentration, increase of branchness and decrease of cold-flow were observed. A series of phosphine compounds was employed to control the microstructure of polybutadiene, and ultra high cis polybutadiene with over 99% cis content was obtained in the presence of tri-p-fluorophenyl phosphine. The vulcanized properties of the three different microstructured polybutadienes, Nd-BR 1, Nd-BR 2, and Ni-BR, such as tensile strength, 300% modulus, elongation at break, and heat build-up, were measured. Linear polymer, Nd-BR 1, showed excellent tensile and dynamic properties such as low heat build-up and high abrasion resistance. However, poor processibility in view of high compound viscosity and hardness was obtained. Nd-BR 2, designed to compromise both processibility and physical properties, exhibited improved processibility in terms of low compound viscosity with good tensile and dynamic properties. Ni-BR showed great advantages in processibility, such as low compound viscosity and hardness, but tensile strength and abrasion resistance were low. It is concluded that the structure of high cis polybutadiene, such as degree of branch, cis and vinyl contents, and molecular weight distributi