Synthesis, characterization, thermal degradation, and comparative chain dynamics studies of weak-link polysulfide polymers

Size Control and Antioxidant Properties of Sulfur-Rich Polymer Colloids from Interfacial Polymerization

High sulfur content polymeric materials, known for their intriguing properties such as high refractive indices and high electrochemical capacities, have garnered significant interest in recent years for their applications in optics, antifouling surfaces, triboelectrics, and electrochemistry. Despite the high interest, most high sulfur-content polymers reported to date are either bulk materials or thin films, and there is a general lack of research into sulfur-rich polymer colloids. Water-dispersed, sulfur-rich particles are anticipated to broaden the range of applications for sulfur-containing materials. In this study, the preparation and size control parameters are presented of an aqueous dispersion of sulfur-rich polymers with the sulfur content of dispersed particles exceeding 75 wt%. Employing polymeric stabilizers with varying hydrophilic-lipophilic balance (HLB), along with changing the rank of inorganic polysulfides, allow for the control of particle size in the range of 360 nm - 1.8 µm. The sulfur-rich colloid demonstrates antioxidant properties in water, demonstrating the potential for the use of sulfur-rich polymeric materials readily removable, heterogeneous radical scavengers.

Halogenated sunflower oil as a precursor for synthesis of polysulfide polymer

Polysulfide polymers usually are prepared by the reaction of different dihalide compounds with disodium polysulfides. In this field, dihalides are expensive and produced from halogenation of organic compounds by different methods with harsh conditions. To overcome this problem, in this work, sunflower oil as polyunsaturated oil was used as precursor to produce polyhalide compound. In this field, double bonds of oil were applied as functional groups to halogenate the sunflower via benzoyl peroxide-catalyzed reaction with hydrochloric acid. Also, Na2S3 was synthesized via the reaction between sulfur and sodium hydroxide. Then, halogenated oil was reacted with Na2S3 to produce sunflower oil-based polysulfide polymer. Fourier transform infrared spectroscopy (FT-IR) and proton nuclear magnetic resonance (1H NMR) were used to characterize the structure of sunflower oil and synthesized polysulfide polymer. The content of halogenation was also obtained via energy-dispersive X-ray spectroscopy (EDX). Thermal stability of synthesized polymer was determined by means of thermal gravimetric analysis (TGA) and glass transition temperature was investigated by differential scanning calorimetry (DSC).

Role of ZDC/S ratio for pervaporative separation of organic liquids through modified EPDM membranes: rational mechanistic study of vulcanization

Variations in crosslink densities and crystallinity due to mono-, di- and poly-sulphide linkages in EPDM vulcanization are achieved using different sulfur/accelerator weight ratios and therefore the separation factor and membrane selectivity of toluene.

Enhanced thermal properties of poly(ethylene tetrasulfide) via expanded graphite incorporation by in situ polymerization method

In this study, a novel poly(ethylene tetrasulfide) (PETS)/expanded graphite (EG) nanocomposite with 40°C improvement in melting point is prepared via in situ polymerization technique. The morphology, chemical characteristics and the structural behavior of nanocomposites are characterized using scanning electron microscopy, Fourier transform infrared spectroscopy and x-ray diffraction (XRD) techniques, respectively. XRD observations show about 0.1 nm increase in d-spacing of PETS crystals in the presence of 2 wt% EG in nanocomposite. This behavior could be related to the intercalation of polysulfide macromolecules in the interlayer structure of EG sheets. Furthermore, the thermal properties of nanocomposites are investigated using differential scanning calorimetry and thermogravimetric analysis techniques. The thermal degradation temperature of nanocomposite containing 2 wt% graphite shows an improvement of about 10°C compared to unfilled polysulfide. Moreover, the chemical resistance of nanocomposites in different common solvents increases in the presence of EG, which could be accounted as a clear proof of interconnections for EG and macromolecular structure of the polymer.

End-group rearrangements in poly(propylene sulfide) matrix-assisted laser desorption/ionization time-of-flight analysis. Experimental evidence and possible mechanisms

RATIONALE

Polysulfides [poly(1,2-alkylene sulfides)] are oxidation-responsive polymers that are finding application in drug release and biomaterials. The precise knowledge of their macromolecular characteristics is of the essence in view of their application to biological systems.

METHODS

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) with and without silver trifluoroacetate was used to characterize a series of polymers with increasing molecular weight in the range 1000-4000 g/mol and with low polydispersity (<1.12).

RESULTS

Well-resolved peaks and accurate mass-measured values were obtained using a 2-(4-hydroxyphenylazo)benzoic acid (HABA) matrix, but significant fragmentations took place in the absence of silver as a cationizing reagent. Elimination reactions appeared to occur at terminal groups and limited depolymerization could be recorded. Interestingly, the most common fragmentation pathway seemed to be based on an as-yet-unreported process of hydrogen transfer requiring the presence both of ester groups and of thioethers.

CONCLUSIONS

The use of an appropriate cationizing reagent (silver trifluoroacetate) appeared to suppress end-group eliminations; we hypothesize that this action is based on the involvement of the terminal groups in silver chelation.