"Molecular structure design and synthesis of star-shaped multi-arm styrene-butadiene copolymer"

A series of star-shaped multi-arm styrene-butadiene copolymers (S-g-SSB-6) were synthesized by living anionic polymerization, with n-butyllithium as initiator, styrene and butadiene as monomers, 2,2-di(tetra-hydrofuran-2-yl) propane as polar structure regulator and hexachlorodisilane as coupling agent. The molecular weight and its distribution, coupling arm number and coupling efficiency of S-g-SSB-6 were characterized by gel permeation chromatogram. The rheological properties of S-g-SSB-6, star-shaped multi-arm styrene-butadiene copolymer with SiCl4 as coupling agent, and linear styrene-butadiene copolymer (L-SSB) were characterized by rotational rheometer, and the effects of branched chain length and branched chain flexibility on the rheological properties of S-g-SSB-6 were also investigated. The results showed that the coupling arm numbers of S-g-SSB-6 reached 4.1, and the coupling efficiency was greater than 80%. S-g-SSB had lower melt viscosity and better fluid flow than those of L-SSB under the same weight-average molecular weight. When the branching degree was the same, the melt viscosity of S-g-SSB-6 increased with the increase of single arm molecular weight and molecular chain rigidity.