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.

Selenium-containing brush polymers with diverse functional segments were easily prepared through diselenide–yne chemistry.

Responsive photonic crystals (PCs) have attracted great interest due to their adjustable structure color.

A selenium-functionalized e-caprolactone was synthesized by introducing a phenyl selenide group at the 7-position. A polymer can be obtained through the ring opening polymerization by using this compound as the monomer in a base/thiourea binary organocatalytic system. A living polymerization process was achieved under mild conditions. The resulting polymers had a controlled molecular weight with a narrow molecular weight distribution and high end-group fidelity. Random copolymers could be obtained by copolymerizing this compound with e-caprolactone. The thermal degradation temperature of the obtained copolymers decreased with the increasing molar ratio of selenide functionalized monomer in copolymers, while the glass transition temperature increased. In addition, the phenyl selenide side group could be further modified to a polyselenonium salt, which resulted in a polymer with good antibacterial properties. The survival rate of E. coli and S. aureus was only 9% with a polymer concentration of 62.5 μg mL-1.

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.

We present a living cationic polymerization of vinyl ethers utilizing electrophilic selenium reagents as initiators and pentacarbonylbromomanganese (Mn(CO)5Br) as the catalyst. The polymerization could be carried out under ambient conditions, i.e. no strict purification of reagents, non-inert atmosphere and room temperature. Poly(vinyl ether)s were obtained with controlled molecular weights while maintaining narrow molecular weight distributions (Đ < 1.2). In this way, different selenium-containing structures could be introduced into chain ends of polymers by using suitable electrophilic selenium reagents. Poly(styrene) prepared by atom transfer radical polymerization (ATRP) followed by brominated selenization was further utilized as a macro-initiator to form the corresponding poly(styrene)-b-poly(isobutyl vinyl ether) copolymers, which offered a new avenue for mechanism transformation polymerization.

A new dynamic C–Se bond-based addition–fragmentation chain transfer (AFCT) reaction of allyl selenides was performed under irradiation without any catalyst. ESR data and theoretical results indicated that the transfer reaction proceeded through a radical mechanism. This new dynamic bond holds great potential for application in smart polymer materials.

Exploration of new strategies for the preparation of novel polymer materials with diverse topological structures and functions is a subject of enduring interest in the area of polymer science. In this work, diselenide–yne polymerization for the efficient preparation of selenium-containing hyperbranched polymers (Se-HBPs) was established, which could proceed with 100% atom efficiency under blue light irradiation without any external catalyst. Through systematic optimization of the reaction conditions, a series of Se-HBPs with controllable molecular weights and well-defined structures were obtained in high yield (up to 99%) and stereoselectivity (E/Z = 93 : 7). This type of polymer has degrees of branching (DB) almost as high as that of dendrimers because each unit is either terminal or fully branched. During the mild and efficient diselenide–yne polymerization, the molecular weight and terminal group of the hyperbranched polymer could be adjusted by an AB2 + A type copolymerization strategy, providing a powerful tool to tailor the properties of hyperbranched polymers. Fluorescent, aggregation-induced emission (AIE) and amphipathic Se-HBPs could be prepared in a one-pot reaction. Notably, the AIE-terminal Se-HBPs showed a “see-saw” fluorescence performance via the combination of AIE and aggregation-caused quenching (ACQ). The amphipathic Se-HBPs could self-assemble to give nanoparticles, which showed good oxidation-responsive properties. Moreover, colloid gold nanoparticles could be prepared by utilizing these Se-HBPs as both stabilizers and reductants, which exhibited sensitive oxidative response to 0.01 wt% H2O2. We believe that the simplicity and versatility of diselenide–alkyne polymerization will open up enormous opportunities for preparing multifunctional smart polymeric materials.

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...

The manganese carbonyl induced cationic reversible addition–fragmentation chain transfer (C-RAFT) polymerization under mild conditions such as visible light, room temperature and even in the presence of small quantities of water is reported. In this method, halide abstraction reaction between organic halide and manganese carbonyl is used to generate the oxidant and initiate radicals. The C-RAFT agents are generated in situ from radical transfer reactions between vinyl ethers and three traditional RAFT agents including xanthate, trithiocarbonate and dithiocarbamate species. Poly(vinyl ether)s with RAFT agent terminated chain ends have been successfully obtained and used as macroRAFT agents for preparation of block copolymers combining RAFT radical polymerization. Poly(isobutyl vinyl ether)-b-poly(vinyl acetate) and poly(isobutyl vinyl ether)-b-poly(methyl acrylate) are successfully prepared. In addition, poly(butyl acrylate)-b-poly(isobutyl vinyl ether) have also been obtained using poly(butyl acrylate) prepared by RAFT radical polymerization as macroRAFT agent. Our results show that poly(vinyl ether)s with controlled molecular weight and narrow molecular weight distribution (

Due to their unique properties, selenium-containing polymers have become one of the research focuses of polymer materials in recent years. First, selenium can transform among various states of selenoxide, selenone, and selenium free radicals, and then be restored under these conditions, which endows these polymers with multiresponsive behaviors, including responses to redox changes, light, radiation, etc. Second, these polymers show characteristic properties. Selenium-containing polymers exhibit unique multiple optical–electrical characteristics, including high photoconductivity, anisotropic thermoconductivity, high piezoelectric and thermoelectric responses, and a high refractive index. Based on these various properties, selenium-containing polymers are regarded as excellent functional polymer materials. Therefore, it is meaningful to synthesize selenium-containing polymers with various structures. This paper principally gives a summary of the organic reactions of organoselenium compounds and reviews the research on the synthesis of selenium-containing polymers via different methods, such as the use of selenium-containing monomers and their polymerization, selenium-containing initiators for polymerization, selenium-containing mediators for controlled polymerization and selenium-containing molecules for the postmodification of polymers. Moreover, applications of selenium-containing polymers are described, including their use as intrinsic high refractive index polymeric materials, oxidative- and reductive-responsive materials, dynamic exchanging polymers, selective metal adsorbents, and catalysts.

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.

This paper describes a novel e-caprolactone monomer modified by a phenylseleno group at the α-position of the carbonyl. Poly(α-phenylseleno caprolactone) (PCLSePh) with a well-controlled molecular weight and narrow molecular weight distribution (Đ < 1.20) was prepared through ring-opening polymerization. Hybrid polymers with properties superior to those of polyester materials were also prepared though selenide-mediated radical polymerizations under UV light irradiation. Subsequently, a carbon–carbon double bond was introduced into the main chain of the polymer by the oxidative elimination of the phenylseleno groups with high efficiency. Various side groups were further introduced into the polymer chain through a nucleophilic thiol–ene reaction. This strategy enables the synthesis of PCL with functional groups that allow the multifunctional integration of polyester materials. Furthermore, this monomer can be copolymerized with e-caprolactone to form both random and block copolymers. The glass transition temperature, crystallinity and degradation rate of the copolymers can be adjusted both by oxidation and tuning the composition of the copolymer.

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.

A versatile protocol for the synthesis of various multiresponsive selenide-containing polymeric architectures was developed by multicomponent polymerization (MCP) of primary diamines, γ-butyroselenolactone and electrophilic reagents. The polymer terminal groups could be easily controlled by changing the ratio of the reaction components.

A direct polymerization based on the addition reactions of electrophilic selenium reagents to alkenes was established. It consists of a one-pot cascade process with the generation of selenyl chloride by in situ breakage of the Se–Se bond using sulfuryl chloride, followed by the addition of the obtained selenyl chloride to the carbon–carbon double bond. The polymerization mechanism was confirmed to be a stepwise mechanism. The resulting polymers were characterized and determined to be linear polymers with a sequence regulated backbone repeating unit of ester-selenide-vinyl chloride. When the proportion of sulfuryl chloride was controlled, vinyl terminal groups and diselenide could be easily introduced at the same time, providing a simple way for further modification and application. The feasibility of monomers derived from low cost and easily available unsaturated natural fatty alcohols such as oleyl alcohol, 5-norbornene-2-methanol, etc., was also investigated. It is worth emphasizing specially that the ester-selenide bridged backbone endowed the polyesters with multi stimuli-responsiveness for practical applications.

A high refractive index polymer was synthesized by the copolymerization of styrene with different functionalized N-phenyl maleimides, phenyloxide (P1), phenylsulfide (P2), and phenylselenide (P3). The effects of the substituent elements, molecular weight and selenium content on refractive indices, thermostability, and the glass transition temperature of the obtained polymers were investigated. The results showed that the refractive index of obtained polymers increased in the order of P3 > P2 > P1. Introducing the maleimide moiety into the polymer side chain improved its thermostablity and enhanced the glass transition temperature. To increase the selenium content, P4 was polymerized with selenium-containing maleimide monomer and 4-phenylselane styrene. An RI as high as 1.869 was obtained for P4 at a wavelength of 633 nm. Furthermore, the redox responsive selenide moiety endowed the selenide functionalized polymers with the property of refractive index transformation under oxidization and reduction conditions, which provided a material with potential application as a redox sensor.

Polymer molecular weight distribution (MWD) is a key parameter of polymers. Here we present a robust method for controlling polymer MWD in controlled cationic polymerizations. A latent mediator strategy was designed and combined with temporal programming to regenerate mediators at different times during polymerization. Both the breadths and shapes of MWD curves were tuned easily by adjusting an external light source. Bimodal, trimodal, and tetramodal distributions were obtained, and the breadths could be varied from 1.06 to 2.09. Polymers with different MWDs prepared by this method had good chain end fidelity, which was demonstrated with successful chain-extension experiments. In addition, the introduction of temporal programming with a computer-controlled single chip for the light source opened an avenue for the use of artificial intelligence in polymer synthesis.

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.

Ring-opening copolymerization (ROCOP) is an effective means to prepare functionalized polyester. In this work, a type of selenide-containing polyesters with controllable structure, molecular weight, and molecular weight distribution was successfully prepared by ROCOP of &gamma, selenobutyrolactone and epoxy compounds. The influence of the catalyst, solvent, and reaction temperature on the reaction efficiency was examined. Then, kinetic study was investigated under an optimized condition. The structure of the copolymers was carefully characterized by nuclear magnetic resonance (NMR), 1H NMR, 13C NMR, and 77Se NMR, Matrix-assisted laser-desorption-ionization time-of-flight mass spectrometry (MALDI-TOF-MS), and size exclusion chromatography (SEC). The resulting polymers showed a linear structure with a sequence regulated backbone repeating unit of ester-selenide. On this basis, some typical epoxides were investigated to verify the scope of the polymerization system. Due to the &ldquo, living&rdquo, /controlled characteristics of this ROCOP, multiblock, amphiphilic, and stereotactic copolymers could be prepared with a pre-designed structure. As expected, the selenide-containing amphiphilic copolymer could self-assemble to micelles and showed an oxidative response.

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...

A novel fluoro-xanthate, 2-((4-fluorophenoxycarbonothioyl)thio)ethyl propanoate, was developed and successfully used as a mediator in the photoinduced controlled radical polymerization of more-activated monomers (methyl acrylate (MA), butyl acrylate, and N-isopropylacrylamide) and a less-activated monomer (vinyl acetate (VAc)). The controlled characteristics of the polymerization were demonstrated by the linearly increasing molar mass with conversion, producing polymers with narrow molar mass distributions (1.14–1.37) for MA and VAc. Furthermore, the block copolymer of PMA-b-PVAc was successfully synthesized through chain-extension using PMA as the macro-RAFT agent and VAc as the second monomer.

A versatile protocol for the synthesis of a variety of multiresponsive diselenide-containing polyesters was investigated. It consists of a one-pot, two-step process with the generation of a selenol by nucleophilic ring opening of γ-butyroselenolactone with a broad range of alcohols in situ, followed by the transformation of the obtained compounds to the corresponding diselenides through a spontaneous oxidative coupling reaction. First, the influence of the catalyst choice, alcohol structure, and solvents on the reaction efficiency was examined. After elaboration of this one-pot reaction, a number of routes, all starting from γ-butyroselenolactone, have been developed for the successful synthesis of linear and crosslinked diselenide-containing polyesters via a mild, straightforward process. The structure of diselenide compounds and polymers was carefully characterized by 1H, 13C, 77Se NMR, FT-IR, HRMS, and SEC. In addition, it has been found that the diselenide-containing polyester networks showed fast reprocessing at a mild temperature (70 °C) or by making use of UV irradiation.

The development of visible-light-activated photoswitches has significantly progressed in the past few decades. Herein, two kinds of photoresponsive azoxy polymers were prepared directly from bis-/trinitro-functionalized monomers via an efficient small molecular synthetic method with ultraviolet/visible light irradiation under metal-free and mild conditions. This strategy avoids the use of metal complexes and toxic compounds, while proceeding with high yields (up to 97%) and excellent selectivity without generating azo, amine, or inorganic compounds. Moreover, polymerization showed an efficient process with very high monomer conversion and perfect selectivity. The obtained main-chain linear and hyperbranched azoxy polymers were characterized by 1H NMR, GPC, UV-vis and FT-IR spectra. The π–π* absorptions of the obtained polymers in the UV-vis spectra showed a significant red-shift to the visible light region. Therefore, the photoisomerization of the prepared polymers can be driven by visible light, representing the first visible-light-driven aromatic azoxy polymer actuators.

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.

For the first time, we combined orthogonal maleimide and thiol deprotections together with thiol-maleimide coupling to synthesize discrete oligomers/macromolecules on gram scale with molecular weight up to 27.4 kDa (128mer, 7.9 g) via iterative exponential growth strategy with degree of polymerization (DP) at 2^n-1. By using the same chemistry, a "readable" sequence-defined oligomer and a discrete cyclic topology were also created. Furthermore, uniform dendrons were fabricated via either sequential growth (DP =〖 2〗^n-1) or double exponential dendrimer growth approach (DP =2^(2^n )-1) with significantly accelerated growth rate. This work offered a versatile, efficient and metal-free platform for construction of discrete oligomers with vast designability and high growth rate, which would greatly facilitate sophisticated structure-property research as well as applications of precise polymer-based materials.

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.