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Sulfur-based polymers are unique renewable materials that are receiving a growing attention. The utilization of elemental sulfur with a variety of monomers in their preparation in the absence of solvents using the inverse vulcanization are granting them green nature and unique properties. Several characterization techniques have been used to evaluate the properties of sulfur-based polymers. However, the complex structure and lack of solubility undermine the applicability of some standard characterization techniques in the usual manners. This article reviews the characterization methods used for the evaluation of various properties of sulfur-based polymers such as chemical, morphological, structural, thermal, rheological and mechanical properties, all of which vary depending on the type of comonomer involved in the reaction and heat treatment conditions. The successful applications of different characterization techniques including Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, nuclear magnetic resonance (NMR), scanning electron microscopy/X-ray energy dispersion (SEM-EDX), X-ray diffraction (XRD), mechanical tester, rheometer, thermal gravimetric analyzer (TGA) and differential scanning calorimetry (DSC) are discussed. The challenges to the evaluation of the properties of sulfur-based polymers and the innovative applications of the conventional techniques to overcome them are also deliberated.

Vegetable oils are a promising class of bioresources for producing green polymeric materials to reduce the dependence on petro-based polymers. In this study, a green copolymer prepared by thermal copolymerization corn oil with sulphur at its molten state is reported for the first time. The proportions of sulphur to corn oil (w/w%) in the reaction mixture were varied in the range of 50/50 to 80/20 and the reactions were carried out at 170°C for 1 h. The obtained copolymers were characterized using Fourier transform infrared (FTIR), thermal gravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and powder X-ray diffraction (PXRD). The percentage of the unsaturated fatty acid portion was found to act as a multifunctional monomer stabilizing polysulphide forming crosslinked structures that vary depending on reactant sulphur content. The obtained copolymers were found to be amorphous thermosets with heavily crosslinked structures and composite morphologies. The copolymers also showed high thermal stability under nitrogen atmosphere. The new copolymers are environmentally friendly hybrid material promoting green chemistry with a potential added value to abundantly available sulphur and corn oil.

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Inverse vulcanization is a facile solvent‐free process, which offers interesting sustainable copolymers from the reaction of sulfur with petro‐based monomers or edible vegetable oils. However, sulfur reaction with the former contradicts green chemistry, whereas the latter reduces the viability of the product and can contribute to the food crisis. Herein, we report the preparation of sulfur‐based polymer (SBP) by the reaction of rubber seed oil, RSO (a non‐edible oil), to produce a sustainable sulfur‐based copolymer for the first time. The properties of the new polymer were evaluated using different techniques such as Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy dispersive X‐rays (SEM‐EDX‐mapping), powdered X‐ray diffractometer (p‐XRD), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The polymer was found to be soluble in tetrahydrofuran, thermally stable to 200 °C, and a low glass transition temperature (−6.41 to −7.85 °C for a polymer with 50 to 70 wt % S). The polymer morphological and DSC analysis demonstrated a uniform surface possessing a small amount of unreacted microscale sulfur particles that is lesser than similar polymers from other oils, which was confirmed by DSC. The P‐XRD analysis revealed the amorphous nature of the copolymer caused by a heavily crosslinked structure. The effect of the post‐polymerization treatment on the properties of the copolymers was also investigated which revealed that increasing the curing temperature or quenching medium temperature increases the glass transition temperature of the copolymer. The polymer properties were dramatically improved by reducing the amount of the unreacted sulfur by the addition of a small amount of 1,3‐diisopropeynyl benzene (crosslinker), leading to 99.75 % sulfur conversion, the highest ever value achieved in such SBPs. It can be concluded that the use of RSO with sulfur enhances the sustainability of SBP and promotes their adding products