Biobased Inverse Vulcanized Polymer from Magnolol as a Multifunctional Ingredient for Carbon-Black-Reinforced Rubber Composites

Inverse vulcanization provides a facile route to transform industrial byproduct sulfur into attractive polymeric materials with a variety of applications. Herein, an inverse vulcanized copolymer (PSM) was synthesized by copolymerization of biomass magnolol and sulfur. PSM presents outstanding intrinsic flame retardancy by the formation of a highly pyrolysis-resistant carbonaceous material during combustion. Especially, it can serve as a multifunctional ingredient when utilized in rubber composites. The presence of polysulfide segments and biphenol moieties enables PSM to cross-link rubber effectively and react with the oxygenic groups on the surface of carbon black (CB), thus resulting in the improvement of CB dispersion and stronger interfacial interaction between a rubber matrix and nanofillers than the conventional sulfur-cross-linked rubber composite. Incorporation of PSM also significantly retards the thermo-oxidation aging of the composites due to its radical scavenging capability. Moreover, the dynamic covalent polysulfide segments in the system confer the PSM-cross-linked rubber material reprocessability and recyclability.