Inverse Vulcanization of Vinyltriethoxysilane: A Novel Interfacial Coupling Agent for Silica-Filled Rubber Composites

Abstract

Sulfur-containing silane coupling agents (SSCAs) are widely incorporated into silica-filled rubber composites to improve silica dispersion and enhance interfacial adhesion, maximizing the potential of silica. However, SSCA synthesis involves multistep procedures and requires organic solvents. In addition, modifying rubber composites with SSCAs has persistent issues, such as low coupling efficiency and uncontrollable structure. Herein, we report the facile synthesis of alkoxysilyl-functionalized polysulfides (SPVs) with a tunable molecular structure (sulfur rank and alkoxysilyl fraction) via inverse vulcanization of vinyltriethoxysilane (VTES) with a copolymer of sulfur and styrene. SPVs serve as interfacial modifiers in silica-filled rubber composites by separately reacting with the silica and rubber chains. In particular, the multiple alkoxysilyl sites in the SPV chain increase the probability of silanization, yielding high coupling efficiency in the rubber composite. Although the molar content of alkoxysilyl groups in SPV1 (the mass feed ratio of VTES and copolymer is 1) is half of that in the most widely used small-molecules SSCAs of bis­(3-triethoxysilylpropyl)­tetrasulfide, stronger interfacial adhesion and better silica dispersion are achieved in SPV1-modified composites, which consequently lead to more improvements on the composite properties. In addition, the advantages of SPV1 as an interfacial modifier in improving the “magic triangle” properties of a practical tread composite have been demonstrated. More importantly, the effects of the SPV molecular structure on silica dispersion and interfacial adhesion have been investigated, providing the fundamentals for unraveling the coupling mechanism and guiding composite property regulation.

Exploring Epoxy-Functionalized Polysulfide as a VOC-Free and Highly Effective Interfacial Modifier for Silica-Filled Rubber Composites

“…The grafting efficiency can be calculated according to the formula below: grafting .25em efficiency = W 2 − W 1 1 − ( W 2 − W 1 ) × m silica m SPVE × 100 % where W 1 and W 2 are the mass losses ranging from 130 to 700 °C for pristine silica and M-silica, respectively; m silica and m SPVE are the feeding weights of silica (8.0 g) and SPVE (1.0 g) in the preparation of M-silica, respectively. Accordingly, the grafting efficiency of SPVE toward silica is calculated to be 57%, which is much higher than that of 37% for TESPT reported in our previous literature . It is likely due to a high reactivity between epoxy and silanol groups as well as multiple epoxy sites in SPVE.…”

On the Mechanism of the Inverse Vulcanization of Elemental Sulfur: Structural Characterization of Poly(sulfur-random-(1,3-diisopropenylbenzene))

“…High sulfur content organosulfur copolymers made via inverse vulcanization have been referred to by different names such as inverse vulcanized polymers and chalcogenide hybrid inorganic/organic polymers (CHIPs), both of which refer to sulfur copolymers with a statistical sequence of S–S bonds in a copolymer backbone with organic comonomers . The high sulfur content of these polymers has imparted intriguing optical and electrochemical properties for emerging applications in infrared optics, − Li–S batteries, ,− self-healing materials, ,− environmental remediation, − agrochemical fertilizers, adhesives, thermoplastic elastomers, rubber vulcanization agents, , and flame retardant materials. , While the inclusion of S–S bonds imparts unusual properties to these materials, it also renders these polymers intractable, which has complicated structural characterization of these materials. To date, either solid-state 13 C NMR spectroscopy of sulfur polymers or solution-state NMR spectroscopy characterization of soluble, oligomeric forms of these materials has been conducted to identify the copolymer microstructures.…”

Interface Coupling in Rubber/Carbon Black Composites toward Superior Energy-Saving Capability Enabled by Amino-Functionalized Polysulfide

“…To date, diverse comonomers including unsaturated compounds, − benzoxazines, , and 1,4-diiodobenzene have been used as the starting materials to copolymerize with sulfur. Due to high sulfur fraction, SPs possess intriguing optical, electrochemical, and thermomechanical properties, showing the prospective application in lenses, , Li–S batteries, , heavy metal adsorbents, , and repairable materials. , Very recently, in virtue of a low S–S bond dissociation energy in polysulfides, we demonstrated that SPs possess high reactivity toward rubber and are highly efficient in crosslinking rubbers. , Moreover, the inverse vulcanized SPs of sulfur and vinytriethoxysilane could act as novel coupling agents in silica-filled rubber composites, exhibiting significant advantages in improving the comprehensive properties of practical tread composites …”

“…37,38 Moreover, the inverse vulcanized SPs of sulfur and vinytriethoxysilane could act as novel coupling agents in silica-filled rubber composites, exhibiting significant advantages in improving the comprehensive properties of practical tread composites. 39 In this work, inspired by these creative contributions, an amino-functionalized polysulfide (PDAS) was synthesized by inverse vulcanization of sulfur and m-phenylenediamine, and PDAS was then explored as a modifier in a CB-filled natural rubber (NR) composite. Specifically, the function mechanism of PDAS is clarified, and its effects on morphology, interfacial adhesion, viscoelasticity properties, and thermo-oxidation aging of the composites are studied.…”