Inverse vulcanization exploits S₈ to synthesize polysulfides. However, evolution of products and its mechanism during inverse vulcanization remains elusive. Herein, inverse vulcanization curves are obtained to describe the inverse vulcanization process in terms of three stages: induction, curing and over-cure. The typical curves exhibit a moduli increment before declining or plateauing, reflecting the process of polysulfide network formation and loosing depending on monomers. For aromatic alkenes, in the over-cure, the crosslinked polysulfide evolves significantly into a sparse network with accelerated relaxation, due to the degradation of alkenyl moieties into thiocarbonyls. The inverse vulcanization product of olefins degrades slowly with fluctuated relaxation time and modulus because of the generation of thiophene moieties, while the inverse vulcanization curve of dicyclopentadiene has a plateau following curing stage. Confirmed by calculations, the mechanisms reveal the alkenyl groups react spontaneously into thiocarbonyls or thiophenes via similar sulfur-substituted alkenyl intermediates but with different energy barriers.

For blending immiscible polymers, such as in the toughening modification of polylactide (PLA) via blending with rubbery materials, interfacial compatibilization is of great significance while the mechanism, especially the role of interfacial rheology, remains elusive. In this study, styrene-butadiene block copolymer elastomer (SBC) was employed to toughen PLA and a dumbbell-shaped Janus nanoparticle (JNP) consisting of polymethyl methacrylate and polystyrene spheres with equal size (∼80 nm) was used as the compatibilizer. Located at the interface, JNPs exhibited a great compatibilization efficiency in PLA/SBC blends, as demonstrated by the good morphology stabilization against droplet coalescence under static annealing and low shear flow conditions, as well as by the resistance against droplet breakup under high shear flow conditions. Moreover, as revealed from the linear viscoelasticity of JNP compatibilized blends, when JNP loading is more than 2 phr, aside from shape relaxation, an interfacial relaxation dominated by Marangoni stress was observed, indicating the possibility of particle redistribution on droplet surfaces. However, when loading is more than 4 phr, relaxations in the terminal zone no longer exist, implying the possible formation of a particle network on the droplet surface. This is consistent with the mechanical properties. The blend shows the greatest toughness at JNP loading around 3 phr, while the toughness is very poor when JNP loading is either too low or too high. This suggests interfacial relaxation to be crucial to guarantee a good toughening effect of SBC in PLA.