Thioether Units Research Articles

Highly Efficient Doping‐Free Thermally Activated Delayed Fluorescent Organic Light‐Emitting Diodes with an Ultrathin Quasi‐Host‐Guest Emission Layer

AbstractDoping‐free organic light‐emitting diodes (OLEDs) are beneficial to reduce manufacturing costs for mass production, which, however, are limited by the ubiquitous aggregation‐caused quenching (ACQ) effect, especially for thermally activated delayed fluorescence (TADF) emitters with relatively long exciton lifetimes. Herein, two typical TADF emitters pACRS and pACRSO with different sulfur atom valence states are developed, where pACRS with a thioether unit exhibits suppressed intermolecular interaction, alleviated ACQ effect, and higher efficiency in a conventional doping‐free device, in contract to pACRSO with a sulfone unit. It is of interest that comparable efficiencies are achieved for both emitters in doping‐free OLEDs with an ultrathin emission layer (UEML), in which the emitter molecules are deposited onto the surface of the underlying organic layer of host material to form an ultrathin quasi‐host‐guest system with alleviated ACQ effect. Besides, the suppressed trap effect is the key to guarantee the efficiency of UEML‐OLEDs, while different intermolecular interactions of emitters that determine the optimized UEML thickness will affect the efficiency roll‐off. Furthermore, benefiting from the UEML structure, highly efficient doping‐free OLEDs are also successfully achieved for red TADF emitters with stronger intermolecular interactions. Such an UEML strategy meeting efficiency and cost demands holds great promise for doping‐free OLEDs.

Direct Radical Copolymerizations of Thioamides To Generate Vinyl Polymers with Degradable Thioether Bonds in the Backbones

Direct radical addition reactions of thiocarbonyl (C═S) groups unaccompanied by β-scission have rarely been reported despite their potential for constructing various sulfur-containing compounds. Herein, we report direct radical copolymerizations of the C═S double bonds of simple thioamide derivatives and the C═C double bonds of common vinyl monomers to produce novel degradable vinyl polymers that contain thioether units in the backbones. In particular, N-acylated thioformamides copolymerized smoothly with various vinyl monomers, such as methyl acrylate, vinyl acetate, N,N-dimethylacrylamide, and styrene. RAFT copolymerization was also successfully mediated. The resultant copolymers had high glass transition temperatures and were readily degradable under ambient conditions. This work will expand the potential for use of thiocarbonyl compounds in radical reactions and develop novel poly(thioether)-vinyl polymer hybrid materials with unusual properties.

Impact of the Heteroatoms on Mobility–Stretchability Properties of n-Type Semiconducting Polymers with Conjugation Break Spacers

The development of stretchable semiconducting polymers through statistical terpolymerization with conjugation break spacers (CBSs) has gained much attention. In this study, we systematically investigated the effects of incorporating CBSs with thioether units into naphthalenediimide (NDI)-based n-type semiconducting polymers on their semiconductivity and stretchability compared to polymers with the corresponding alkyl- and ether-based CBSs. Indeed, six NDI-based semiconducting polymers with CBSs composed of di(ethylene sulfide), tetra(ethylene sulfide), di(ethylene oxide), tetra(ethylene oxide), octylene, and tetradecylene units were synthesized by statistical terpolymerization based on Migita–Kosugi–Stille cross-coupling reactions of 5,5′-bis(trimethylstannyl)-2,2′-bithiophene (2T), 4,9-dibromo-2,7-bis(2-decyltetradecyl)benzo[lmn][3,8]phenanthroline-1,3,6,8-tetraone (Br-NDI-Br), and CBSs. The experimental results indicate that heteroatom-based CBSs would sufficiently affect solid-state packing, intrinsic stretchability, and mobility retentions of the corresponding polymers. Although all of the polymers demonstrated strong edge-on orientations, those with ether-based CBSs displayed the lowest crystallinity among them. This result was attributed to the phase separation induced by highly polar ethylene oxide moieties, leading to inferior charge transport performances and low crack onset strain. In contrast, the thin film of the polymer with thioether-based CBSs showed delayed crack onset strain and a high dichroic ratio. The narrower bond angle of C–S–C (98.9°) than C–O–C (113.3°) calculated by the DFT method led to a more bent conformation along the polymer backbone, which provided a strain-releasing capability to realign the polymer chains. Consequently, the polymers with thioether-based CBSs displayed higher mobility–stretchability properties than those comprising ether-based CBSs. This is the first report on the design, synthesis, and application to organic field-effect transistors (OFETs) of stretchable n-type semiconducting polymer materials, clarifying the impact of heteroatoms on the mobility–stretchability properties of n-type semiconducting polymers with new CBSs having ethylene oxide and ethylene sulfide units.

Incorporating tertiary amine and thioether in polyarylene sulfide sulfone membranes for multiple separations

Polymers have been widely applied for membrane separations; however, most polymer membranes lack adjustable pores and cannot serve in multiple separations once fabricated. Here, a novel block copolymer, polyarylene sulfide sulfone/amide tertiary amine (PASS/ATA), containing tertiary amine and thioether groups was designed for membrane fabrication as it can be self-assembled into a well-defined, uniform, and continuous pores. Via a facile oxidization procedure, the tertiary amine and thioether groups in the membrane molecular chains were converted into amine oxide and sulfone groups, respectively, which dramatically narrows down the pores of the membranes and greatly improves dye rejection, altering the application of the membranes from ultrafiltration (UF) to nanofiltration (NF). Furthermore, after the thioether units were oxidized into sulfone groups, the solvent resistance of the membranes was greatly increased, ensuring the application of the oxidized membranes in organic solvent nanofiltration (OSN). Dissipative particle dynamics (DPD) simulation was applied to shed insight on the formation mechanisms and transformation processes, as well as to explain the decrease of pore size combined with the enhancement of solvent resistance. As a result, combing tertiary amines with thioether groups in polymer chains endows the membrane with multiple functionalities, allowing for multiple separations including UF, NF, and OSN.

Preparation of chlorine resistant thin‐film‐composite reverse‐osmosis polyamide membranes with tri‐acyl chloride containing thioether units

AbstractA novel tri‐acyl chloride monomer containing reductive thioether units (T‐TDC) was prepared. It was conducted to partially replace trimesoyl chloride (TMC) and react with m‐phenylenediamine (MPD) by interfacial polymerization to prepare a series of T‐TDC/TMC/MPD copolymer thin‐film‐composite reverse‐osmosis polyamide membranes. Through this routine, the reductive thioether units was introduced into the film molecular chain to protect amide bonds from being chlorinated by oxidizing during the membrane cleaning process. The enhanced chlorine resistance of these resultant membranes was revealed by FT‐IR and XPS characterization: it could be found thioether was prior to amide oxidation, and its oxidation process can be divided into two steps (the thioether units was first converted to sulfoxide groups, and then further oxidized to sulfone groups). Through this routine, the active chlorine was consumed partially, then the amide bond was protected. The experiment result is consistent with the DFT theoretical calculation. The chlorine exposure concentration of the normalized flux and rejection decreased to 1 increased gradually with the addition of copolymerization ratio of T‐TDC, especially for the sample 20%‐TTDC‐TFC, its chlorine exposure concentration was 3 and 4 times higher respectively than that of 0%‐TTDC‐TFC when its normalized flux and rejection at 1. In addition, it can be found that the polar sulfone and sulfoxide groups can form hydrogen bonds to prevent the membrane from degrading immediately. This method provides an effective way for improving the service life of RO film.

Enhancing chlorine resistance in polyamide membranes with surface & structure modification strategies

Abstract Higher efficient reverse osmosis (RO) membrane development is a significant issue due to the payoff among salt rejection and water flux and permissive chlorine attacking and fouling potential. Weak chlorine resistance is a distinctive challenge for composite polyamide thin-film reverse osmosis membranes. A commercial aromatic membrane was modified by grafting nitrogen-doped graphene oxide quantum dots (N-GOQDs) to enhance chlorine resistance, embedding two-dimensional MXene Ti3C2Tx, introducing synthetically reductive thioether units and oxidized graphitic carbon nitride (OGCN). In this work, salt rejection, chlorine resistance, and water flux increased compared to the pristine membrane. Comprehensive arrangement of desalination performance and chlorine resistance was achieved by varying time and concentrations of prepared chemicals. For instance, improved chlorine resistance, after 12 hours of grafting time by N-GOQDs doped membrane, was 32.8%, after 6 hours of exposure time by MXene Ti3C2Tx membrane was 27.4%, after 1 hour of exposure time by thioether membrane was 28.1% and after 40 hours of doping time by OGCN membrane was 31.3%. N-GOQDs doped membrane showed a good chlorine resistant property, but on the other hand, thioether nano units showed other properties more effectively, including water flux, salt rejection, and less reaction time.

Low efficiency roll-off thermally activated delayed fluorescence emitters for non-doped OLEDs: Substitution effect of thioether and sulfone groups

The non-doped organic light-emitting diodes (OLEDs) based on thermally activated delayed fluorescence (TADF) materials are attracting increasing attentions due to the excellent performance and simple fabrication. We report an effective design strategy of TADF emitters to improve the non-doped performance by adjusting the valence state of the S atom in TADF molecules and utilizing the steric hindrance effect. Two novel TADF materials PT-BZ-DMAC and PS-BZ-DMAC were designed and synthesized with benzophenone acceptor and acridine donor. In particular, the thioether or sulfone group was attached to benzophenone. Remarkably, the bluish-green TADF-OLED with non-doped PT-BZ-DMAC turned on at 2.5 V and realized a maximum external quantum efficiency (EQE) of 17.34%, which was comparable with its doped OLED (17.71%) but showed much slower roll-off. At 100 and 1000 cd m−2, the non-doped PT-BZ-DMAC device still maintained acceptable efficiencies at 14.65% and 12.59%. In contrast, sulfone-modified PS-BZ-DMAC exhibited good efficiency of 20.55% only in doped OLED. The single crystal analysis and DFT calculation revealed that the phenyl thioether unit in PT-BZ-DMAC hardly contributes to the LUMO or the electronic transitions, instead determines the highly twisted geometry and acts as the barrier group, finally improving the performance of PT-BZ-DMAC in neat film device.

Design of recyclable, fast-responsive and high temperature shape memory semi-aromatic polyamide

Development of high temperature shape memory polymers with fast response time and recyclable performance is highly desired. In this study, a new semi-aromatic tri-amine (TRIA) containing thioether unit is prepared through the reaction of trifluoro-monomer and p-mercaptoaniline (p-MA). It is conducted to polymerize with 4,4′-thiodibenzoyl chloride (TDC) and different ratios of diamine (both of them contained flexible thioether group) to supply a series of slightly crosslinking semi-aromatic polyamide. It is found that the resultant polymers had excellent thermal properties (Tg, 237.9–245.8 °C, Td, 430.9–436.5 °C) and mechanical properties (tensile strength, 74–100 MPa). Because of the introduction of the large amount of flexible thioether group, the resultant polyamides can be dissolved in some aprotic solvents, and can be processed with solution method to fabricate a series of fast-responsive shape memory film (SMF) with a responsive time of 6–8 s, recovery rate of 98–99.5% after 20 cycles. What's more, the oxidized film can even lift a weight equal to about 2–3 times (vertical direction) and 5–8 times (horizontal direction) of its own weight. Interestingly, unlike other shape memory polymers, these SMF after multiple processes (after bending-recovery cycle at high temperature) can still be processed repeatedly with a solution route, which supplies a novel and recyclable candidate for excellent performance SMP. It is expected to be used in solar cell wingspan actuator to light the satellite weight.

Thiol-Ene Cationic and Radical Reactions: Cyclization, Step-Growth, and Concurrent Polymerizations for Thioacetal and Thioether Units.

Thiol-ene cationic and radical reactions were conducted for 1:1 addition between a thiol and vinyl ether, and also for cyclization and step-growth polymerization between a dithiol and divinyl ether. p-Toluenesulfonic acid (PTSA) induced a cationic thiol-ene reaction to generate a thioacetal in high yield, whereas 2,2'-azobisisobutyronitrile resulted in a radical thiol-ene reaction to give a thioether, also in high yield. The cationic and radical addition reactions between a dithiol and divinyl ether with oxyethylene units yielded amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively. Under high-dilution conditions, the cationic and radical reactions resulted in 16- and 18-membered cyclic thioacetal and thioether products, respectively. Furthermore, concurrent cationic and radical step-growth polymerizations were realized using PTSA under UV irradiation to produce polymers having both thioacetal and thioether linkages in the main chain.

Thiol‐Ene Cationic and Radical Reactions: Cyclization, Step‐Growth, and Concurrent Polymerizations for Thioacetal and Thioether Units

AbstractThiol‐ene cationic and radical reactions were conducted for 1:1 addition between a thiol and vinyl ether, and also for cyclization and step‐growth polymerization between a dithiol and divinyl ether. p‐Toluenesulfonic acid (PTSA) induced a cationic thiol‐ene reaction to generate a thioacetal in high yield, whereas 2,2′‐azobisisobutyronitrile resulted in a radical thiol‐ene reaction to give a thioether, also in high yield. The cationic and radical addition reactions between a dithiol and divinyl ether with oxyethylene units yielded amorphous poly(thioacetal)s and crystalline poly(thioether)s, respectively. Under high‐dilution conditions, the cationic and radical reactions resulted in 16‐ and 18‐membered cyclic thioacetal and thioether products, respectively. Furthermore, concurrent cationic and radical step‐growth polymerizations were realized using PTSA under UV irradiation to produce polymers having both thioacetal and thioether linkages in the main chain.

Preparation and characterization of thin-film-composite reverse-osmosis polyamide membrane with enhanced chlorine resistance by introducing thioether units into polyamide layer

In this study, chemically reductive thioether units were introduced into the polyamide (PA) layer of a thin film composite (TFC) reverse osmosis (RO) membrane to enhance its chlorine resistance. The sulphur moieties could be oxidized to partially capture chlorine, therefore protecting the membrane from being chlorinated. The thioether units were introduced into the PA layer by partially replacing trimesoyl chloride (TMC) with 4, 4′-thiodibenzoyl chloride (TDC) in the organic phase during interfacial polymerization. Both ATR-FTIR and XPS investigations revealed that the thioether units had been incorporated into the PA layer successfully. In addition, the introduced thioether units were also uniformly dispersed, as confirmed by the STEM-EDS results. The introduction of the thioether units influenced the morphology of the membrane significantly, which in turn markedly impacted its performance. The introduction of thioether groups was found to have a positive effect on improving the chlorine resistance of the TFC membrane. Taking the 60%-TDC-TFC membrane as an example, the chlorine exposure (95 ppm h) at which the normalized flux fell below 1 was much higher than that of the pure membrane (34 ppm h) when chlorinated in an acidic environment. Under alkaline conditions, the chlorine exposure (30,430 ppm h) at which the normalized rejection decreased to less than 1 was approximately three times of that of the pure membrane (10,839 ppm h). One step of the potential mechanism revealed by the ATR-FTIR and XPS results involved the incorporated thioether units consuming part of the chlorine and undergoing oxidation. Another involved the fact that both the produced sulfoxide and sulfone groups could form hydrogen bonds with the neighbouring hydrogens, which would replace the hydrogen bonds destroyed by chlorination.

Aromatic polyesters containing different content of Thioether and methyl units: facile synthesis and properties

A series of aromatic polyesters containing thioether units were successfully synthesized in this paper. Two kinds of aromatic dichloride, (4,4’-thiodibenzoyl chloride (T-DC) and 4,4’-bis(4-chloroformylphenylthio)benzene (BPB-DC) with different sulfur content were prepared and reacted with bisphenol through interfacial reaction. These four kinds of aromatic polyesters were found to have excellent thermal and mechanical properties. Their glass transition temperatures (Tg) were in the range of 161.2–216.9 °C, the initial degradation temperatures (Td) was up to 400–454 °C and tensile strengths of 68.9–114.9 MPa. Additionally, these aromatic polyesters present good optical transmittance within the range of 81.19–84.54% at 450 nm. More importantly, all polyesters exhibited outstanding flame retardant properties. The limiting oxygen indexes (LOIs) were ranged from 30 to 39 and UL-94 V-0 rating can be reached via this approach. In summary, the comprehensive performance of the four designed polyesters surpassed the traditional aromatic ones such as U-100.

Core-Cross-Linked Nanoparticles Reduce Neuroinflammation and Improve Outcome in a Mouse Model of Traumatic Brain Injury.

Traumatic brain injury (TBI) is the leading cause of death and disability in children and young adults, yet there are currently no treatments available that prevent the secondary spread of damage beyond the initial insult. The chronic progression of this secondary injury is in part caused by the release of reactive oxygen species (ROS) into surrounding normal brain. Thus, treatments that can enter the brain and reduce the spread of ROS should improve outcome from TBI. Here a highly versatile, reproducible, and scalable method to synthesize core-cross-linked nanoparticles (NPs) from polysorbate 80 (PS80) using a combination of thiol-ene and thiol-Michael chemistry is described. The resultant NPs consist of a ROS-reactive thioether cross-linked core stabilized in aqueous solution by hydroxy-functional oligoethylene oxide segments. These NPs show narrow molecular weight distributions and have a high proportion of thioether units that reduce local levels of ROS. In a controlled cortical impact mouse model of TBI, the NPs are able to rapidly accumulate and be retained in damaged brain as visualized through fluorescence imaging, reduce neuroinflammation and the secondary spread of injury as determined through magnetic resonance imaging and histopathology, and improve functional outcome as determined through behavioral analyses. Our findings provide strong evidence that these NPs may, upon further development and testing, provide a useful strategy to help improve the outcome of patients following a TBI.

Chemically stable thioether cross-linked membranes derived from sulfonated poly(arylene ether ketone)s for direct methanol fuel cells

A series of thioether cross-linked membranes based on sulfonated poly(arylene ether ketone)s containing propenyl groups were prepared to solve the problem of high methanol permeability for proton electrolyte membrane in direct methanol fuel cells (DMFCs). For this purpose, 4,4′-thiobisbenzenethiol was selected as cross-linker, and the cross-linked structure was formed via thiol-ene click chemical reaction between propenyl and thiol groups. Compared with pristine membrane, the thioether cross-linked membranes exhibited improved mechanical properties and dimensional stabilities. As the cross-linker increased, the swelling ratio decreased from 11.01% to 8.64% at 20°C and from 15.18% to 10.69% at 80°C. Furthermore, the modified membranes exhibited reduced methanol permeability coefficients (down to 4.03 × 10−7 cm2 s−1), which was nearly half of the pristine membrane (7.66 × 10−7 cm2 s−1). Due to the thioether units, the cross-linked membranes showed enhanced oxidative stabilities, and the longest elapsed time in Fenton’s reagent was 225 min, which was 2.5 times longer than that of pristine polymeric membrane. Although the proton conductivity decreased upon the addition of cross-linker agent, the selectivity value increased due to the lower methanol permeability. Thus, all the results implied that the thioether cross-linked membranes were promising alternative materials for DMFCs application.

Synthesis and metal complexation of dual-functionalized silsesquioxane nanoparticles by sequential thiol–epoxy click and esterification reactions

Here, we demonstrate a convenient and robust method for fabricating a series of dual-functionalized silsesquioxane nanoparticles (SQ-NPs) using a thiol–epoxy click reaction and subsequent esterification. Epoxy-functionalized SQ-NP was initially prepared from commercially available (3-glycidyloxypropyl)triethoxysilane. A thiol compound, 2-mercaptopyridine, was used in the thiol–epoxy click reaction, and sulfur-containing acid chloride derivatives were used for subsequent functionalization via esterification. The resulting SQ-NPs have two chemically different groups on a single arm, which affords a high density of peripheral functional groups. The dual-functionalized SQ-NPs with the pyridine and thioether units led to the complexation with copper species, affording a stable Cu complex. This convenient synthetic approach provided dual-functionalized SQ-NPs with narrow size distributions (average particle diameter<3nm), reasonable molecular weights (Mn=3300–4200, Mw/Mn=1.32–1.45), good solubility, relatively high refractive indices, and the ability to form characteristic metal complexes.

Poly(ether–thioethers) by Thiol–Ene Click and Their Oxidized Analogues as Lithium Polymer Electrolytes

A family of nine poly(ether–thioethers) (PETEs) were synthesized by the radical coupling of a dithiol and a divinyl ether to investigate the importance of organo-sulfur incorporation in solid polymer electrolytes. Two series of four polymers each were synthesized to probe both the effect of the carbon spacer length between thioether units and of the ratio of ether to thioether units. PETE samples from these two series had low Tg values, ranging from −50 to −75 °C, and all but two PETEs displayed crystallinity. Molecular weights between 7 and 13 kg/mol were obtained for all polymers. Taking advantage of the sulfur-centered functional group, a single polymer, PETE-1, was selectively oxidized to the poly(ether–sulfoxide) PESO-1 and the poly(ether–sulfone) PES-1. Oxidation increased the Tg of PETE-1 from −64 °C to −36 and −26 °C for PESO-1 and PES-1, respectively, while all three were amorphous. Of the nine new PETE polymers, two were amorphous and the addition of LiTFSI decreased the extent of crystallinity ...

Semi-aromatic polyamides containing methylene and thioether units: synthesis and membrane properties

The membranes of the resultant semi-aromatic polyamides showed good corrosion resistance, mechanical and thermal properties.

Protecting‐Group‐Free Solid‐Phase Anchoring of Polyphenolic C‐Glucosidic Ellagitannins and Synthesis of 1‐Alkylamino‐Vescalagin Derivatives (Eur. J. Org. Chem. 23/2014)

The cover picture shows a protecting-group-free approach for the chemo- and stereoselective amination of the C-glucosidic ellagitannin vescalagin. This bioactive plant polyphenol is a characteristic secondary metabolite of fagaceous woody species such as oak (Quercus sp.). Its benzylic secondary alcohol group is first substituted by a thioether unit, which is then activated by the use of a sulfenyl chloride. The resulting thiosulfonium ion reacts with primary amines to afford β-1-alkylamino-vescalagin derivatives. This article by S. Quideau et al. on p. 4963 ff describes this selective amination of such a structurally unique plant polyphenol by a protocol that was adapted to both solution- and solid-phase synthesis conditions. The background picture shows an oak tree hundreds of years old, which is certainly packed with vescalagin, as the amount of this ellagitannin can reach up to 2 %percnt; by weight of dry heartwood.

A convenient approach to amphiphilic hyperbranched polymers with thioether shell for the preparation and stabilization of coinage metal (Cu, Ag, Au) nanoparticles

Partially functionalized hyperbranched polyglycerols with thioether units have been straight forwardly prepared, leading to globular polymers with core-shell structure. They are been used as an excellent platform for the preparation and stabilization of long-term stable coinage metal nanoparticles such as copper (less than 4 nm) and silver (1 to 2 nm) nanoclusters, as well as aggregated gold nanoparticles (12 nm).

Poly(arylene ether sulfone) containing thioether units: synthesis, oxidation and properties

The resultant PASSs after oxidation had excellent corrosion resistance. They did not dissolve in NMP and concentrated H2SO4.