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Inverse vulcanization utilizes alkenyl monomers and elemental sulfur, an excessive by-product of oil and gas refineries, to synthesize dynamically crosslinked sulfur-rich polymers, therefore providing a new way to construct sustainable and versatile materials. The inverse vulcanization of the biological extracts and natural polymers gives rise to a variety of bio-based polysulfides aligning with the concept of green chemistry. In this paper, the development of synthesis strategies, corresponding mechanisms, scope of renewable cross-linking agents, and the properties as well as the potential applications of polysulfides are reviewed. In particular, the progress in the preparation of various polysulfides from fossil resources to bio-based counterparts is deliberated with multiple modification methods elucidated. The bio-derived polysulfides are proved to be outstanding materials and prominent alternatives for traditional petroleum-based products especially for the use as effective ion absorbents, Li-S battery cathode materials, adhesives and controlled release fertilizers, etc. Finally, a few prospects and challenges about the future of these intriguing sulfur-based polymers are raised and discussed. [ABSTRACT FROM AUTHOR]

The development of high toughness as well as flame‐retardant polylactic acid (PLA) materials is important for expanding the practical applications. Herein, a type of high toughness PLA composites with improved flame retardancy was developed through combining modified carbon nanotubes (CNT) and polysiliconoxaborane (PBSi) with PLA matrix. The optimal PLA composite (PLA/PBSi/CNT‐3.0) exhibited excellent crystallization degree (18.7%), thermal stability (the Ea significantly increased), flame retardancy (the values of peak heat release rate (PHRR) polarized optical microscopy and total heat release (THR) decreased to 287.1 W/g and 15.5 kJ/m2, respectively), and mechanical properties (the elongation at break increased to 149.5%, with an increasement of 1745.7%) due to the combined action of flexible chain segments and hydrogen bonding interactions. Furthermore, the toughening mechanism of the PLA/PBSi/CNT composites was illustrated and attributed to the combination of flexible SiOBO segments and two dominant energy dissipation processes (the breakage of hydrogen bond and the destruction of microcrystals). Overall, this work provided a facile approach for improving the toughness and flame retardancy of PLA, which was conducive to expanding the application range of PLA. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. Inverse vulcanization exploits elemental sulfur to synthesize versatile polysulfides but the mechanism of inverse vulcanization remains elusive. Herein, the authors use inverse vulcanization curves to describe the three-stage structural evolution during the inverse vulcanization process. [ABSTRACT FROM AUTHOR]