The synthesis and modification of low relative molecular weight polybutadiene oligomers

Bulk precipitation polymerization and solution polymerization of butadiene with supported titanium catalyst TiCl₄/MgCl₂-Al(i-Bu)₃ using hydrogen as molecular weight regulator has been performed to synthesize low molecular weight oligomers of trans-1,4-polybutadiene. The effect of the polymerization conditions on the relative molecular weight and structure of the polymer have been studied. Increasing the hydrogen pressure and polymerization temperature resulted in the decrease of intrinsic viscosity of the polymer. By changing the hydrogen pressure, the mole percentage of trans-1,4-unit in the as-obtained polybutadiene can be adjusted, and the maximum value could reach 97%. The degree of crystallinity of the as-synthesized oligomers was about 8–50% with the melting point of form β at about 130–140°C and form α at about 50°C. Through the grafting maleic anhydride, the polar groups were introduced onto the polybutadiene macromolecular chain, which could broaden the application of the non-polar polybutadiene.