Using conjugated system from natural sources for the synthesis of sulfur copolymers by bi‐function catalysts at mild temperatures

Abstract

Sulfur‐rich polymers are promising materials to cover several applications including mercury capture adsorbents. Tung oil, a natural conjugated triene triglyceride oil, were selected to prepare sulfur‐rich copolymers. The unique second monomer made reaching the gel point possible at a mild temperature of 130°C in 2.5 h. The reaction accomplishment was confirmed by the depletion of double bonds in tung‐oil‐sulfur copolymers measured by 1H NMR, FTIR, XRD, and DSC. A bi‐function catalyst calcium hydroxide accelerates the reactions between triglyceride and sulfur before it is removed to increase the surface area and achieve the aims of preparing adsorbents, which has zero free sulfur, high crosslinking degree, and efficient mercury capture. Newly developed tung‐oil‐sulfur copolymers catalyzed by calcium hydroxide offer the possibility to synthesize sulfur‐rich copolymers that combine the advantages of the high performance and the utility of greener and more environmental friendly raw materials.

The exploration of the inverse vulcanization mechanism of tung oil by controlling the oxygen and moisture presence during reactions

“…The inverse vulcanization system is tung oil, for which it was found that its unique conjugated triene tremendously decreased reaction temperature compared with the non-conjugated double bonds in normal lipids like sunflower oil. 29 The experimental results obtained from particular reaction conditions would reflect whether trace impurities are beneficial or detrimental to the copolymerization and provide evidence to confirm or disprove the mechanisms proposed by other researchers.…”

“…Others in our research group demonstrated that sunflower oil does not polymerize with S 8 at 130°C. 29 To confirm the initiating role of conjugated trienes in tung oil, a mixed vegetable oil with 50% tung oil (1 g) and 50% sunflower oil (1 g) was used to react with sulfur (2 g). Experiments showed that mixed vegetable oil reacted with sulfur at 130°C, and produced poly (S50-TO-50-SFO) which was lighter in color and softer in texture.…”

“…An enormous number of potential applications [9][10][11] of sulfur-rich materials have been reported, including cathode material for rechargeable batteries, [12][13][14] materials with high refractive indexes, 15,16 IR optical materials, repairable materials, [17][18][19] adhesives, 19,20 fertilizers, [21][22][23][24][25] and composite materials. 26,27 An extensive range of substances was successfully used to synthesize sulfur-rich polymeric materials [12][13][14][28][29][30] but selecting the second monomer seemed to be a random process. Their similarity in molecular structure is at least one of the following: double bonds (conjugated or non-conjugated), 31 aromatic 32,33 or benzene ring, and nucleophilic system.…”

“…But the significant difference between the properties of polymeric materials from vegetable oils in the presence or absence of DEDC hinted that the inner structures may be massively different and thus their reaction mechanism too. 29,39 From this, it can be speculated that the mechanism of inverse vulcanization is a mixture of a radical mechanism and an anionic one, and the dominant route might be one of them under different conditions such as temperature lower or higher than 159°C and the usage of catalysts.…”

Green and sustainable natural derived polysulfides for a broad range of applications

“…Lyu et al introduced Ca(OH) 2 as a catalyst for inverse vulcanization, which could reduce the polymerization time, increase the conversion yield of sulfur and act as a porogen agent through copolymerization of tung oil with sulfur. 126 For instance, at an oil : sulfur ratio of 1 : 1, the reaction could be completed in 30 min and the amount of free sulfur in the polysulfide was reduced to zero. A comparison of the removal rate of Hg 2+ from HgCl 2 solutions (2000 mg L −1 ) showed that the porous polysulfides prepared in the presence of Ca(OH) 2 could remove up to 75% of Hg 2+ , whereas the value for non-porous polysulfides was around 65%.…”