Search

Diselenide, as a dynamic covalent bond, has been widely applied in functional materials due to its response to light, heat, sonication, pH, and other stimuli. Herein, a polarization-induced metathesis mechanism for diselenides under heating conditions in the dark is proposed. First, a radical trap experiment is used to prove that the exchange reaction of diselenides in the dark does not involve any radicals. Second, the dynamic exchange reaction of diselenides is found to be affected not only by the polarity of the solvent but also by the introduction of polar groups into the molecular skeleton. Furthermore, DFT calculations also support the notion that polarity has a large effect on the heterolytic rather than homolytic bond dissociation energies. The experimental results for allyl selenide small molecules, polymers, and polymer materials catalyzed by diselenide all support the polarization-induced metathesis mechanism. In short, we successfully enhanced the understanding of the mechanism for diselenide metathesis.

Photoinduced polymerization is an attractive technique with the advantages of easy operation, mild conditions, and excellent temporospatial controllability. However, the application of this technique in step-growth polymerization is highly challenging. Here, we present a catalyst-free, visible-light-induced step-growth polymerization method utilizing a photo-RAFT single-unit monomer insertion reaction between the xanthate and vinyl ether groups. Benefitting from this reaction, a pendant cationic RAFT agent can be generated in each repeating unit of the polymer backbone. Both cationic and radical side chain extensions were successfully realized, providing a facile approach for the postpolymerization of step-growth polymers for the development of various functional polymeric materials.

Three-dimensional (3D) printing utilizing controlled polymerization systems is emerging as a powerful approach to fabricate "living" objects, which can be further modified with various functionalities. Here, we report photoinduced free radical-promoted cationic reversible addition-fragmentation chain transfer (RAFT) polymerization under broad wavelengths from ultraviolet (UV) to near-infrared (NIR) light. A commercially available iron catalyst, cyclopentadienyl iron dicarbonyl dimer (Fe

Developing biodegradable cationic polymers with high antibacterial efficiency and low cytotoxicity is of great significance in biological applications. Selenium is an essential trace element for the human body, and selenium-containing compounds are promising in various health-related applications. To combine selenium with biodegradability, selenide-functionalized polycaprolactones (PCL) with different hydrophobic substituents were synthesized followed by selenoniumization. The optimal polyselenonium salt showed excellent antibacterial activity with an MBC of 2 μg mL

We present a robust manganese-catalyzed cationic reversible addition-fragmentation chain transfer (RAFT) polymerization induced by visible light. Well-defined poly(vinyl ether)s with controlled molecular weight and molecular weight distributions (MWDs) can be conveniently prepared at room temperature without monomer purification. The commercially available manganese carbonyl bromide is used as the photocatalyst for cationic RAFT polymerization. Moreover, this method has been further applied in both batch and continuous flow systems, providing a visible light induced flow cationic polymerization under mild conditions.

A near-infrared (NIR) light induced controlled cationic polymerization is presented here. The halide abstraction reaction between the cyclopentadienyl iron dicarbonyl dimer (Fe2(Cp)2(CO)4) and an o...

The unstable PbSe quantum dot (QD) surface requires tedious and complicated synthetic protocols and renders them substantially underdeveloped compared to PbS QDs. Here, we describe a direct synthes...

Selenium-doped phenolic resin spheres (Se-RS) was synthesized by the reaction of 4,4′-selenodiphenol and resorcinol with formaldehyde catalyzing by ammonia. The whole reaction was completed within 5 min under the acceleration of ultra-sonication. Se-RS with controlled Se-content and Se-distribution were prepared in such manner. The obtained Se-RS showed enhanced Pd2+ and Au3+ adsorption capacity in aqueous solution. The adsorbed Au3+ can be further reduced to Au0 at the surface of Se-RS in situ without additional reducing agent. The Se-RS exhibited exceptional extract capacity of gold from e-waste sewage and other aqua even its Au3+ concentration was extremely low.

A robust method for preparing controlled poly(vinyl ethers) utilizing commercially available reagents under visible light is reported. Pentacarbonylbromomanganese (Mn(CO)5Br), generated from the conventional photolysis of manganese carbonyl and halide abstraction, is considered as a catalyst to oxidize carbon radical to carbenium ion in this polymerization. Polymerization behavior including the effects of solvents and monomers have been investigated.

Selenium-containing monomer (p-phenylseleno) styrene (p-PhSeSt) is polymerized by reversible addition-fragmentation chain transfer polymerization. Polymer, (P(p-PhSeSt)), with controlled molecular weight and narrow molecular weight is obtained. The selenide moiety in obtained P(p-PhSeSt) can be selectively oxidized to selenoxide or selenone groups by H2 O2 or NaClO, respectively. These oxidized groups can be further reduced to selenide by Na2 S2 O4 . The structure changing of polymers during such redox cycle is characterized by nuclear magnetic resonance, X-ray photoelectron spectroscopy, and size exclusion chromatography. Properties, such as thermal performance, glass transition temperature, water contact angles, and refractive indices, of the resulting polymers are systematically investigated before and after oxidation. In addition, SiO2 inverse opal photonic crystal (IOPC) is fabricated by sacrificial polymer colloidal template method. Owing to changes of the RIs of P(p-PhSeSt) after selective oxidation, the predictable change of PC bandgap as a redox-responsive PC sensor is successfully realized, which provides new perspectives for modulating photonic crystals.

On-demand dissolution of hydrogels is being increasingly studied for their potential use in burn wound dressing applications. Herein, a dynamic diselenide-containing hydrogel is developed through a very simple one-pot and two-step process starting from the selenol functionalization of a partially hydrolyzed poly(2-ethyl-2-oxazoline) with γ-butyroselenolactone. The hydrogel spontaneously cross-links via an in situ oxidation of the selenol functionalities in air. The gelation process and the final viscoelastic properties of the gel are characterized by rheological experiments. The mechanical properties of those new diselenide-containing hydrogels are easily tuned by varying the concentration of γ-butyroselenolactone. The materials also show good skin adhesion and UV light responsiveness. A unique feature of the hydrogel is its capability to be fully and rapidly dissolved on-demand, via oxidation or reduction of the diselenide cross-links, making them particularly attractive for burn wound dressing applications.

A method combined spray-drying process with light-induced reversible addition fragmentation chain transfer (RAFT) polymerization was used to synthesize N-doped carbon spheres (N-CS). Firstly, the common used carbon precursor phenolic resin which called Resol was modified with a chain transfer agent (CTA). Then, the mixed ethanol solution of CTA modified Resol, F127, TEOS, and HCl was used as starting material. After a typical spray-drying process, uniformed and discrete composite spheres in regular size (70 μm) were obtained. The RAFT polymerization of acrylonitrile was initiated under the irradiation of blue LED at the surface of spheres. Through such manner, controlled amount of polyacrylonitrile was introduced onto the surface of carbon sphere. After calcination at 900 °C and etching, the obtained porous N-CS (60 μm) showed controllable total N content up to 10.8 wt%, tunable high surface area up to 1130 m2/g and good CO2 absorptivity which can up to 4.34 mmol/g at 273 K and 4.13 mmol/g at 298 K at 1.0 bar.

Poly(2-oxazoline)-based biomaterials have shown significant potential for various applications in the past decade. Herein, we present a methodology for the design of degradable diselenide-cross-linked nanofibers by aqueous electrospinning of selenol (SeH)-modified poly(2-ethyl-2-oxazoline) (PEtOx). The selenol groups have been introduced into PEtOx by reacting partially hydrolyzed PEtOx (poly(2-ethyl-2-oxazoline-)-co-ethylenimine (PEtOx-EI)) with γ-butyroselenolactone, whereby ring-opening upon reaction with the secondary amine groups in the polymer backbone yields selenol side chains. Subsequent aqueous electrospinning of the selenol-containing PEtOx was found to lead to in situ cross-linked water-stable nanofibers, ascribed to the formation of diselenide cross-links. The effects of changes in the experimental parameters and the influence of the selenium content on the electrospinning process were investigated in detail. Dynamic exchange between the remaining free SeH groups and diselenide bonds formed u...

Herein, p-phenylseleno styrene (p-PhSeSt) and 4-(1,2,2-triphenylvinyl)phenyl acrylate (TPE-a) were copolymerized by photo-induced reversible addition-fragmentation chain transfer (RAFT) polymerization under blue light at room temperature. The selenide moiety in resulting copolymers could be selectively oxidized to selenoxide or selenone groups by H2O2 or NaClO, respectively, which caused the changing of structure and performance of the copolymer. The structure changing of copolymers during the oxidation was characterized by nuclear magnetic resonance and size exclusion chromatography. Properties of the resulting polymers were systematically investigated before and after oxidation, such as thermal performance, glass transition temperature, water contact angles and refractive indices. In addition, due to the change of hydrophilicity and hydrophobicity of the polymers in aqueous solution after oxidation, the detection of Au3+ and nitrobenzene were successfully realized, constructing a versatile and multifunctional fluorescent probe sensor, which provides potential application prospects for the detection of oxidations.

To investigate the complexity of breaking aryl C Se bond, alkyl C Se bond and alkyl C S bond by ultraviolet light, three maleimide polymers are employed as objects, including SePhP which reported in our previous work having aryl C Se bond, SePP which synthesized via radical copolymerization of N-(4-selenophenyl)-propyl maleimide and styrene having alkyl C Se bond and SPP which synthesized via radical copolymerization of N-(4-thiophenyl)-propyl maleimide and styrene having alkyl C S bond. After careful structure characteristics, SePhP, SePP and SPP are treated by ultraviolet light, as a result, only C Se bond of SePP can be broken. When SePP is irradiated by ultraviolet light in an oxygen-free condition, it can make a structure change from linear to cross-linked and refractive index decrease of polymer. Furthermore, utilizing photo-crosslinking and changing of refractive index of SePP after ultraviolet light irradiation, we realize visual photomask patterning in a simple system, which will bring great potential in display devices, anti-counterfeit labels, and etc.

Poly(glycidyl methacrylate) (PGMA) was synthesized by Fe(0)-mediated living radical polymerization followed with post-modification by PhSeZnCl. A series of selenide functionalized PGMAs with different selenium concentrations and molecular weights were obtained. The introduction of selenide groups into PGMA resulted in a polymer with high refractive index. The relationships between the concentration of selenium, degree of polymerization and refractive index were investigated. Results showed that the refractive index of the final polymer could be adjusted by the concentration of selenium and degree of polymerization, which provided a useful way to fabricate polymeric materials with adjustable refractive index.

A versatile protocol for the synthesis of a variety of multiresponsive diselenide-containing polymeric architectures was investigated. It consists of a one-pot, two-step process with the generation of a selenol by in situ nucleophilic ring opening of selenolactone with a broad range of amine-containing structures, followed by the transformation of the obtained compounds to the corresponding diselenide through a spontaneous oxidation coupling reaction. After elaboration of this one-pot reaction, a number of routes based on selenolactones have been developed for the successful synthesis of functional, linear, branched, cyclic, and cross-linked polymers via a mild, straightforward process. Moreover, the polymer end groups can be easily modified by changing the ratio of amine and selenolactone or sequential Michael addition of selenol to the methacrylic ester. At last, the self-healing properties of the diselenide-containing networks were determined by exposing a cut sample of the polymer to UV light.

Pendant selenium-containing maleimide polymers with different selenium contents are synthesized via a radical copolymerization of styrene and N-butylmaleimide phenyl selenide. The polymer structures are characterized by nuclear magnetic resonance, gel permeation chromatography, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and scanning electron microscopy with an energy-dispersive spectrometer, which results in the desired structures and selenium contents. The refractive indices of the polymers, which change as a function of different contents of selenium and oxidative stimuli by H2 O2 or O3 , are investigated. Finally, a photonic crystal (PC) is prepared based on the selenium-containing polymer. The visible color changes of the PC are investigated as a function of different concentrations and contact times of O3 .

Soluble high refractive index polyimides have extensive applications in optical devices due to their ease of processing and versatility. In this work, selenide-containing polyimides were designed and synthesized via amine-dianhydride polycondensation. Two selenide containing diamines, e.g. bis(3-trifluoromethyl-4-aminophenyl)selenide (BTFAPS) and bis(4-aminophenyl)selenide (BAPS) were reacted with 4,4′-(Hexafluoroisopropylidene)diphthalic anhydride (6FDA) for the preparation of selenide containing polyimides. Comparison with its oxygen and sulfur counterparts, the selenide-containing PIs have better solubility, higher refractive index, and can bring redox responsiveness. This is due to the trifluoromethyl base, which possesses a large free volume, and the selenium element, which has a higher molar refraction and redox activities than even sulfur. Various techniques, such as nuclear magnetic resonance, gel permeation chromatography, Fourier transformed infrared spectroscopy and wide angle X-ray diffraction were used for characterizing the polymers structure. Differential scanning calorimetry, thermogravimetric analysis, ultraviolet-visible spectroscopy, spectroscopic ellipsometry and X-ray photoelectron spectroscopy were used to characterize the properties of the polymers.

Vinyl acetate is polymerized in the living way under the irradiation of blue light-emitting diodes (LEDs) or sunlight without photocatalyst at ambient temperature. 2-(Ethoxycarbonothioyl)sulfanyl propanoate is exclusively added and acts as initiator and chain transfer agent simultaneously in the current system. Poly(vinyl acetate) with well-regulated molecular weight and narrow molecular weight distribution (Đ < 1.30) is synthesized. Near quantitative end group fidelity of polymer is demonstrated by nuclear magnetic resonance (NMR) and matrix-assisteed laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Herein, the first example of photosensitive cyclic amphiphilic homopolymers consisting of multiple biphenyl azobenzene chromophores in the cyclic main chain tethered with hydrophilic tetraethylene glycol monomethyl ether units is presented. The synthetic approach involves sequentially performed thermal catalyzed "click" step-growth polymerization in bulk, and Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) intramolecular cyclization from α-alkyne/ω-azide linear precursors. It is observed that such amphiphilic macrocycles exhibit increased glass transition temperatures (Tg ), slightly faster trans-cis-trans photoisomerization, and enhanced fluorescence emission intensity compared with the corresponding linear polymers. In addition, the cyclic amphiphilic homopolymers self-assemble into spherical nanoparticles with smaller sizes which possess slower photoresponsive behaviors in a tetrahydrofuran/water mixture compared with those of the linear ones. All these interesting observations suggest that the cyclic topology has a great influence on the physical properties and self-assembly behavior of these photoresponsive amphiphilic macrocycles in general.

The atom transfer radical polymerizations (ATRPs) of styrene initiated by diselenocarbamates were carried out for the first time. The polymerization showed first-order kinetic with respect to the monomer concentration, and the molecular weights of the obtained polymers increased linearly with the monomer conversions with narrow molecular weight distribu- tions (as low as 1.16). The results of chain extension, 1 H NMR, UV-vis, and MALDI-TOF MS confirmed that the resultant poly- styrene possessed some degree of living diselenocarbamates terminal. However, significant amounts of dead polymers (about 53%) were also found. This work offered an alternative type of ATRP initiator, and the seleno-terminated polymers may be useful in biotechnological and biomedical applications. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 00, 000-000

Diselenide-containing polymers are facilely synthesized from polymers prepared by atom transfer radical polymerization (ATRP). Benefiting from the ATRP technology, this protocol provides a flexible route for controlling the polymer structure, which allows for a great variety of architectures of selenium-containing polymer materials for applications in various fields. The oxidative and reductive responsive behavior of the obtained diselenide-containing polymers is also investigated.

A novel strategy for the synthesis of main-chain Azo polymers directly from bisnitroaromatic compounds by the photocatalytic process has been achieved under mild conditions. This approach avoids the tedious synthesis of Azo monomers and proceeds with a high monomer conversion (∼100%) and excellent selectivity (∼100%) but without generating a significant amount of inorganic wastes and impurities (Cu2+ or azoxy groups) existing in main-chain Azo polymers compared to previous methods. The polymerization was monitored by UV–vis, FT-IR, and MALDI-TOF-MS, indicating that the reaction process proceeded with formation of the azoxy repeating units from the corresponding bisnitroaromatic monomers and the reduction of corresponding azoxy repeating units to the azo repeating units. Furthermore, the recyclable heterogeneous photocatalysts represent an attractive green process for production of main-chain Azo polymers.

In this article, the polymerization behavior has been investigated utilizing phenyl(4-vinylbenzyl)selane (PVBS) as an inimer under ultraviolet irradiation. Corresponding copolymers and homopolymers were synthesized by copolymerization PVBS with styrene and homopolymerization itself. The branching factors (g′) of these branched polymers were characterized along with the polymerization conditions. Moreover, the results showed that the obtained polymers' refractive index (RI) can be enhanced by the introducing of selenium element. The results also indicated that the RI of obtained polymers could be adjusted extendedly by changing selenium content in them. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 504–510

An iron-mediated reverse ATRP of methyl methacrylate (MMA) is successfully carried out in water in the absence of any dispersants, using a water-soluble 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50) as the initiator and the stabilizer, and using an oil-soluble N,N-butyldithiocarbamate ferrum (Fe(S2 CN(C4 H9 )2 )3 ) as the catalyst without adding any additional ligands. Micron-sized PMMA particles with UV light-sensitive -S2 CN(C4 H9 )2 end group are obtained, and monomer droplet nucleation and suspension polymerization mechanism are proposed. Polymerization results demonstrated typical "living"/controlled characteristics of ATRP: first-order polymerization kinetics, linear increase of molecular weights with monomer conversion and narrow molecular weight distributions for the resultant PMMA particles. NMR spectroscopy and chain-extension experiments under UV light irradiation confirm the attachment and livingness of UV light-sensitive -S2 CN(C4 H9 )2 group in the chain end.

The living free radical polymerizations of vinyl acetate (VAc) were successfully achieved in the presence of a novel organic selenium compound (diselenocarbonates), with 2,2′-azobisisobutyronitrile (AIBN) as the initiator. The living characteristics of the VAc polymerization were confirmed by the linear first-order kinetic plots and linear increase of molecular weights (Mn) of the polymers with monomer conversions, while keeping the relatively low molecular weight distributions. In addition, the end of the polymers contains selenium element which may be useful in biotechnological and biomedical applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3159–3165

Diselenide-containing polymers have attracted more and more attention due to their redox sensitivity and bioapplication. In this work, a bifunctional diselenocarbonate is prepared and used to mediate the reversible addition-fragmentation chain transfer (RAFT) polymerization, producing α,ω-selenocarbonate-labeled telechelic polystyrene. Based on effective aminolysis of the terminal selenocarbonates and the followed spontaneous oxidation coupling reaction of diselenols, monoblock cyclic polystyrene linked by one diselenide bond and multiblock cyclic copolymer linked by several diselenide bonds are prepared by manipulating the concentration of α,ω-telechelic polystyrene in solution. The progress of aminolysis and the subsequent spontaneous oxidation of selenols to diselenides are monitored by UV-vis, gel permeation chromatography (GPC), and NMR characterizations, confirming the cyclic topologies of the resultant polymers (monocyclic or multiblock cyclic polymer). The monoblock cyclic or multiblock polymers show redox sensitivity, which can be converted to linear polymer by reducing or oxidizing agent. Moreover, the obtained monoblock cyclic polymer or multiblock cyclic copolymer can be transformed to each other under UV irradiation by adjusting the concentration of the cyclic polystyrene. For the first time, this work provides an alternative and promising approach to realize the topological transformation of polymers by installing multiresponsive diselenide moities into the backbone of cyclic polymer.

P,P-Diphenyl phosphinodiselenoic acid benzyl ester was synthesized and used as a mediator for the polymerization of styrene under UV–vis irradiation. Moderately controlled evidence was found: linear polymerization kinetics, linear evolution of molecular weight with monomer conversion, and relatively narrow molecular weight distribution (1.5–2.0). The structure of the obtained polymers was characterized using NMR and oxidative eliminaton. Based on polymerization results, an iniferter mechanism was proposed for the current polymerization system. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

The combo agent with roles of initiator and chain transfer agent was demonstrated in RAFT polymerization of styrene. Polymers with defined structures at both α and ω ends were obtained, which was verified by the successful synthesis of seven-block segments of PS and PMA by sequential addition of monomers in one pot.

Mn(OAc)3-mediated direct Csp2–H radical trifluoromethylation of coumarins with CF3SO2Na (Langlois reagent) to afford selective 3-trifluoromethyl coumarins in moderate to good yields is described. This methodology can also be applied to the trifluoromethylation of quinolinones and pyrimidinones.

The application of selenol-X chemistry in nucleophilic substitution and Se-Michael addition reactions for polymer chain end modification is presented. Selenol-labeled polystyrene can easily react with alkyl halides, methyl methacrylate, methyl acrylate, pentafluorostyrene, etc. The mild conditions make it attractive for the synthesis of macromonomers. The resulting polymers are analyzed and characterized by UV, size-exclusion chromatography (SEC), NMR, and matrix assisted laser desorption/ionization time of flight mass spectroscopy.

Butyl acrylate is polymerized in the living way under the irradiation of purple light-emitting diode (LED) or sunlight without photocatalyst at ambient temperature. 2-((Phenoxycarbonothioyl)thio) ethyl propanoate) is exclusively added and acted as an initiator and a chain transfer agent simultaneously in the current system. Poly(butyl acrylate) with well-regulated molecular weight and relatively narrow molecular weight distribution (Ð 95%) can be achieved within several minutes. Polymerization shows oxygen tolerance. Near quantitative end-group fidelity of polymer is demonstrated by 1H NMR and matrix-assisted laser desorption/ionization time-of-flight mass spectra.

A facile soap-free miniemulsion polymerization of methyl methacrylate (MMA) was successfully carried out via a reverse ATRP technique, using a water-soluble potassium persulfate (KPS) or 2,2'-azobis(2-methylpropionamidine) dihydrochloride (V-50) both as the initiator and the stabilizer, and using an oil-soluble N,N-n-butyldithiocarbamate copper (Cu(S2CN(C4H9)2)2) as the catalyst without adding any additional ligand. Polymerization results demonstrated the "living"/controlled characteristics of ATRP and the resultant latexes showed good colloidal stability with average particle size around 300-700 nm in diameter. The monomer droplet nucleation mechanism was proposed. NMR spectroscopy and chain-extension experiments under UV light irradiation confirmed the attachment and livingness of UV light sensitive -S-C(=S)-N(C4H9)2 group in the chain end.

Mn(III)-mediated phosphonations of carbon–carbon double and triple bonds to form alkenylphosphonates are introduced.

Reactions of diphenylphosphinoyl radicals with 5-aryl-2-pentenoates or β-phenylethylene styrenes generate trans-substituted tetrahydronaphthalenes through a cascade reaction sequence.