Synthesis of high crystalline syndiotactic 1,2-polybutadienes and study on their reinforcing effect on cis-1,4 polybutadiene

A novel compound diethyl acetylphosphonate has been explored as efficient additive in iron based catalyst for stereo-polymerization of 1,3-butadiene to afford high crystalline 1,2-syndiotactic polybutadiene. Excellent 1,2 selectivity in range of 91.0–98.4% with controllable crystallinity has been achieved at high catalytic efficiency in wide ranges of cocatalyst and additive feeding as well as at large temperature scope. As reinforcing agent, two crystalline polymers differing in crystallinity 4.4% and 51.9% are blended and co-cured with cis-1,4 polybutadiene (PB) with 10 wt-%, providing samples PB1 and PB2, respectively. SEM from the sample fracturesurface shows the s-PBD particles are intimately mixed and homogeneously dispersed in PB matrix due to the strong interfacial interaction. The analysis of the mechanical properties of sample PB2 finds the tensile strength of increases by one-fold and the elongation at break increases by two-fold when head to head comparison to those of the CB filled PB, while the shear modulus G′ and loss factor (tan δ) are as good as those charged with CB. These results highlight the role of s-PBD as reinforcing agent of PB rubber, yielding high performance rubber materials with improved mechanical properties.