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Chalcogenide hybrid inorganic/organic polymers (CHIPs) are a new class of optical polymeric materials for imaging and photonic applications due to their high refractive indices and high optical transmission at visible and infrared wavelengths. In this study, we characterize these polymers to study the refractive index and delve into the electronic properties by way of measurements of their dielectric constants. Ellipsometry is used to determine the refractive indices for wavelengths from 500 nm to 12 µm, while we use capacitance measurements on thin film capacitors with a range of areas to find the dielectric constant. The results are in line with expectations based on the sulfur composition of the polymers-indices range from 1.7 to 1.85, and dielectric constants range from 2.6 to 3. With these measurements, these sulfur polymer materials are established to be good candidates for optical and photonic applications, particularly with respect to telecommunications. The dielectric constants suggest that applications such as electro-optic devices and capacitors may also be viable.

 

Multiple relaxation times are used to capture the numerous stress relaxation modes found in bulk polymer melts. Herein, inverse vulcanization is used to synthesize high sulfur content (≥50 wt%) polymers that only need a single relaxation time to describe their stress relaxation. The S-S bonds in these organopolysulfides undergo dissociative bond exchange when exposed to elevated temperatures, making the bond exchange dominate the stress relaxation. Through the introduction of a dimeric norbornadiene crosslinker that improves thermomechanical properties, we show that it is possible for the Maxwell model of viscoelasticity to describe both dissociative covalent adaptable networks and living polymers, which is one of the few experimental realizations of a Maxwellian material. Rheological master curves utilizing time-temperature superposition were constructed using relaxation times as nonarbitrary horizontal shift factors. Despite advances in inverse vulcanization, this is the first complete characterization of the rheological properties of this class of unique polymeric material.

 

A molecular catalyst attached to an electrode sur-face can in principle offer the advantages of both homogeneous and heterogeneous catalysis. Unfortunately, some molecular catalysts constrained to a surface lose much or all of their solution performance. In contrast, we have found that when a small molecule [2Fe–2S] catalyst is incorporated into metallopolymers of the form PDMAEMA–g–[2Fe–2S] (PDMAEMA = poly(2-dimethylamino)ethyl methacrylate) and adsorbed to the sur-face, the observed rate of hydrogen production increases to kobs > 105 s-1 per active site with lower overpotential, increased life-time, and tolerance to oxygen. Herein, the electrocatalytic performances of these metallopolymers with different length polymer chains are compared to reveal the factors that lead to this high performance. It was anticipated that smaller metallopolymers would have faster rates due to faster electron and proton transfers to more accessible active sites, but the experiments show that the rates of catalysis per active site are largely independent of the polymer size. Molecular dynamics modelling reveals that the high performance is a consequence of adsorption of these metallopolymers on the surface with natural assembly that brings the [2Fe–2S] catalytic sites into close contact with the electrode surface while maintaining exposure of the sites to protons in solution. The assembly is conducive to fast electron transfer, fast proton transfer, and a high rate of catalysis regardless of polymer size. These results offer a guide to enhancing the performance of other electrocatalysts with incorporation into a polymer that provides optimal interaction of the catalyst with the electrode and with solution. 

Dithiophosphoric acids (DTPAs) are an intriguing class of compounds that are sourced from elemental sulfur and white phosphorus and are prepared from the reaction of phosphorus pentasulfide with alcohols. The electrophilic addition of DTPAs to alkenes and unsaturated olefinic substrates is a known reaction, but has not been applied to polymer synthesis and polymer functionalization. We report on the synthesis and application of DTPAs for the functionalization of challenging poly‐enes, namely polyisoprene (PI) and polynorbornene (pNB) prepared by ring‐opening metathesis polymerization (ROMP). The high heteroatom content within DTPA moieties impart intriguing bulk properties to poly‐ene materials after direct electrophilic addition reactions to the polymer backbone introducing DTPAs as side chain groups. The resulting materials possess both enhanced optical and flame retardant properties vs the poly‐ene starting materials. Finally, we demonstrate the ability to prepare crosslinked polydiene films with di‐functional DTPAs, where the crosslinking density and thermomechanical properties can be directly tuned by DTPA feed ratios.

 

Dithiophosphoric acids (DTPAs) are an intriguing class of compounds that are sourced from elemental sulfur and white phosphorus and are prepared from the reaction of phosphorus pentasulfide with alcohols. The electrophilic addition of DTPAs to alkenes and unsaturated olefinic substrates is a known reaction, but has not been applied to polymer synthesis and polymer functionalization. We report on the synthesis and application of DTPAs for the functionalization of challenging poly‐enes, namely polyisoprene (PI) and polynorbornene (pNB) prepared by ring‐opening metathesis polymerization (ROMP). The high heteroatom content within DTPA moieties impart intriguing bulk properties to poly‐ene materials after direct electrophilic addition reactions to the polymer backbone introducing DTPAs as side chain groups. The resulting materials possess both enhanced optical and flame retardant properties vs the poly‐ene starting materials. Finally, we demonstrate the ability to prepare crosslinked polydiene films with di‐functional DTPAs, where the crosslinking density and thermomechanical properties can be directly tuned by DTPA feed ratios.

 

The production of elemental sulfur from petroleum refining has created a technological opportunity to increase the valorization of elemental sulfur by the synthesis of high-performance sulfur-based plastics with improved optical, electrochemical, and mechanical properties aimed at applications in thermal imaging, energy storage, self-healable materials, and separation science. In this Perspective, we discuss efforts in the past decade that have revived this area of organosulfur and polymer chemistry to afford a new class of high-sulfur-content polymers prepared from the polymerization of liquid sulfur with unsaturated monomers, termed inverse vulcanization.