Carbonate Linkages Research Articles

Degradation of poly(vinyl sulfone carbonate) in aqueous media

A cyclic vinyl sulfone carbonate monomer has previously been developed and used to prepare degradable polymers through ring-opening copolymerization with cyclic ester monomers such as L-lactide. The resulting polymers have the advantage of being functionalized by reaction of the pendant vinyl sulfone moiety. However, the hydrolytic susceptibility of repeating units of the vinyl sulfone carbonate was never examined. Herein, we demonstrate that block copolymers prepared with this monomer and using methoxy poly(ethylene glycol) and 4-arm poly(ethylene glycol) as initiators are readily hydrolysable in micelle form in pH 7.4 phosphate buffer, whereas non-water soluble poly(vinyl sulfone carbonate) is resistant to hydrolysis, exhibiting little mass loss over 32 weeks. A degradation mechanism was proposed for the block copolymer micelles wherein the backbone carbonate linkage is susceptible to nucleophile attack by a hydroxyl ion due to the metal ion coordinating with the pendant thioether-vinyl sulfone group allowing access of hydroxyl ions to the carbonyl carbon of the carbonate group. The non-water soluble poly(vinyl sulfone carbonate) is only very slowly hydrolyzed due to restricted water access to the polymer backbone. Further, the block copolymers remained hydrolytically degradable following reaction of the pendant vinyl sulfone. These findings should prove useful for the broader application of this monomer in developing functionalized biodegradable polymers.

Bio-based non-flammable foams with a circular end-of-life based on the self-foaming process

For conventional polymeric foams, over-utilization of harmful precursors and the problem with waste management are driving scientists to develop sustainable foaming methods and make polymeric foams from renewable precursors. This study developed a self-foaming system to create a lignin carbonate foam (LCF) from two non-toxic carbon storage precursors: lignin and ethylene carbonate (EC). Specifically, kraft lignin, in its isolated salt form, referred to as lignophenolate, is copolymerized with EC via the anionic ring-opening polymerization. Under the optimal condition, the gelation and solidification of the copolymers could coincide with trapping in-situ generated CO2 blowing gas from the copolymers to make the foams. Its unique composition endows the materials with comparable performances with those benchmark plastic foams (for example polyurethane foam, expanded polystyrene) considering the mechanical performances, thermal stability, shape fidelity, and non-flammability. Moreover, the carbonate linkages in LCFs render them to be reshaped or depolymerized with valuable precursors for end-of-life recycling. This study opens new avenues to fabricate polymeric foams from carbon storage precursors through a self-foaming process for applications in the construction industry.

Bisphenol A release from food and beverage containers - A review.

Dietary exposure was introduced as the primary way Bisphenol A (BPA) enters the human body. Although significant efforts have been made to analyze BPA's presence in different foodstuffs, less attention has been given to introducing the conditions that facilitate BPA release. This review aimed to mention possible factors affecting BPA release into foods and beverages. According to the results, the critical factors in BPA release are temperature, manufacturing process, food and packaging type, pH, mineral elements, repeated use, irradiation, washing, contact time, and using detergents. It showed that using PC containers, high temperature and pH, storage under solar irradiation, alkaline detergents, water hardness, and repeated use could increase the BPA release from containers into foodstuff. During various conditions, hydrolysis of the carbonate linkage and d-spacing will increase. Considering these parameters and limiting the use of PC containers, the potential risk of BPA exposure could be eliminated.

Analyzing the network structure of risk transmission among renewable, non-renewable energy and carbon markets

The linkage of renewable, non-renewable energy and carbon markets is increasing, and there is a complex network structure for the risk transmission among multiple markets. Based on the methods of network topology analysis and DY spillover index, this paper analyzes the time-varying spillover effect and network structure of risk transmission among renewable, non-renewable energy and carbon markets. The results show that: according to the static spillover index, there are significant spillover effects among renewable, non-renewable energy and carbon markets, and they are asymmetric. Moreover, the total spillover index further shows that the spillover effect between energy and carbon markets is time-varying, especially during the extreme events. Specifically, the net spillover index shows that the spillover effects among renewable, non-renewable energy and carbon markets are bidirectional, asymmetric and time-varying. Additionally, under the influence of various extreme events, the spillover effect and network structure of risk transmission among renewable, non-renewable energy and carbon markets are heterogeneous. Compared with the shale oil revolution and the Sino-US trade dispute, the influence of COVID-19 is more significant and complex, and it is long-term and comprehensive. Finally, some policy implications for preventing risk transmission and optimizing the energy structure to promote emission reduction are put forward.

Three-Component Donor-π-Acceptor Covalent-Organic Frameworks for Boosting Photocatalytic Hydrogen Evolution.

Two-dimensional covalent-organic frameworks (2D COFs) have recently emerged as great prospects for their applications as new photocatalytic platforms in solar-to-hydrogen conversion; nevertheless, their inefficient solar energy capture and fast charge recombination hinder the improvement of photocatalytic hydrogen production performance. Herein, two photoactive three-component donor-π-acceptor (TCDA) materials were constructed using a multicomponent synthesis strategy by introducing electron-deficient triazine and electron-rich benzotrithiophene moieties into frameworks through sp2 carbon and imine linkages, respectively. Compared with two-component COFs, the novel TCDA-COFs are more convenient in regulating the inherent photophysical properties, thereby realizing outstanding photocatalytic activity for hydrogen evolution from water. Remarkably, the first sp2 carbon-linked TCDA-COF displays an impressive hydrogen evolution rate of 70.8 ± 1.9 mmol g-1 h-1 with excellent reusability in the presence of 1 wt % Pt under visible-light illumination (420-780 nm). Utilizing the combination of diversified spectroscopy and theoretical prediction, we show that the full π-conjugated linkage not only effectively broadens the visible-light harvesting of COFs but also enhances charge transfer and separation efficiency.

Ring-opening copolymerization of CO2 with epoxides catalyzed by binary catalysts containing half salen aluminum compounds and quaternary phosphonium salt

The synthesis and characterization of two different categories of Al(III) compounds supported by unsymmetrical phenoxy-imine ligands with furan-2-ylmethanimine and thiophen-2-ylmethanimine side arms is described. Reactions of the ligands with Al(CH3)3 in a 1:1 and 2:1 stoichiometric ratio resulted in the formation of the corresponding monosubstituted and disubstituted Al(III) compounds in quantitative yields. These compounds were fully characterized using various spectroscopic techniques and elemental analysis. Single-crystal X-ray diffraction studies revealed that the Al(III) center in the monosubstituted compounds adopt a distorted tetrahedral geometry while those in the disubstituted compounds adopt a distorted trigonal bipyramidal geometry with a geometric index τ = 0.72. These compounds along with tetraphenylphosphonium chloride (TPPCl) form a binary catalyst system for the ring-opening copolymerization (ROCOP) of CO2 with cyclohexene oxide (CHO) and propylene oxide (PO). They show notable activity producing alternating polycarbonate with TOF up to 107 h−1 and high selectivity (carbonate linkages > 80%). The catalytic activities of the compounds have been investigated by varying the substituent in the phenolate core and in the imine backbone.

Turning Red without Feeling Embarrassed─Xanthenium-Based Photocages for Red-Light-Activated Phototherapeutics.

Herein, we present high-yielding, concise access to a set of xanthenium-derived, water-soluble, low-molecular-weight photocages allowing light-controlled cargo release in the green to red region. Very importantly, these new photocages allow installation of various payloads through ester, carbamate, or carbonate linkages even at the last stage of the synthesis. Payloads were uncaged with high efficiency upon green, orange, or red light irradiation, leading to the release of carboxylic acids, phenols, and amines. The near-ideal properties of a carboxanthenium derivative were further evaluated in the context of light-controlled drug release using a camptothecin-derived chemotherapeutic drug, SN38. Notably, the caged drug showed orders of magnitude lower efficiency in cellulo, which was reinstated after red light irradiation. The presented photocages offer properties that facilitate the translation of photoactivated chemotherapy toward clinical applications.

Structural Fusion Yields Guest Acceptors that Enable Ternary Organic Solar Cells with 18.77 % Efficiency

AbstractThe design and selection of a suitable guest acceptor are particularly important for improving the photovoltaic performance of ternary organic solar cells (OSCs). Herein, we designed and successfully synthesized two asymmetric silicon–oxygen bridged guest acceptors, which featured distinct blue‐shifted absorption, upshifted lowest unoccupied molecular orbital energy levels, and larger dipole moments than symmetric silicon–oxygen‐bridged acceptor. Ternary devices with the incorporation of 14.2 wt % these two asymmetric guest acceptors exhibited excellent performance with power conversion efficiencies (PCEs) of 18.22 % and 18.77 %, respectively. Our success in precise control of material properties via structural fusion of five‐membered carbon linkages and six‐membered silicon–oxygen connection at the central electron‐donating core unit of fused‐ring electron acceptors can attract considerable attention and bring new vigor and vitality for developing new materials toward more efficient OSCs.

Structural Fusion Yields Guest Acceptors that Enable Ternary Organic Solar Cells with 18.77 % Efficiency.

The design and selection of a suitable guest acceptor are particularly important for improving the photovoltaic performance of ternary organic solar cells (OSCs). Herein, we designed and successfully synthesized two asymmetric silicon-oxygen bridged guest acceptors, which featured distinct blue-shifted absorption, upshifted lowest unoccupied molecular orbital energy levels, and larger dipole moments than symmetric silicon-oxygen-bridged acceptor. Ternary devices with the incorporation of 14.2 wt % these two asymmetric guest acceptors exhibited excellent performance with power conversion efficiencies (PCEs) of 18.22 % and 18.77 %, respectively. Our success in precise control of material properties via structural fusion of five-membered carbon linkages and six-membered silicon-oxygen connection at the central electron-donating core unit of fused-ring electron acceptors can attract considerable attention and bring new vigor and vitality for developing new materials toward more efficient OSCs.

Synthesis of cyclic polymers containing various backbones by means of non-stoichiometric Suzuki-Miyaura polycondensation through intramolecular catalyst transfer

Cyclic polymers bearing various backbones are selectively synthesized by means of non-stoichiometric Suzuki-Miyaura polycondensation of 1.0 equivalent of diboronate monomers containing carbon–carbon double bond (C=C), ester, ether, and carbonate linkages with 1.3 equivalents of meta- or para-dibromophenylene in the presence of t-Bu3PPd G2 precatalyst and CsF/18-crown-6 as a base. The molecular weight of the cyclic polymers increases with increasing monomer concentration. The obtained polymer containing C=C is cyclic even in the high-molecular-weight region, as confirmed by end-group analysis after degradative cross-metathesis reaction of the obtained polymer with an excess of an olefinic small molecule. This non-stoichiometric A2 + B2 Suzuki-Miyaura polycondensation is expected to be a powerful tool for the synthesis of cyclic polymers containing various functional groups in the backbone.

Cationic tetranuclear macrocyclic CaCo3 complexes as highly active catalysts for alternating copolymerization of propylene oxide and carbon dioxide.

We found that a cationic hetero tetranuclear complex including a calcium and three cobalts exhibited high catalytic activity toward alternating copolymerization of propylene oxide (PO) and carbon dioxide (CO2). The tertiary anilinium salt [PhNMe2H][B(C6F5)4] was the best additive to generate the cationic species while maintaining polymer selectivity and carbonate linkage, even under 1.0 MPa CO2. Density functional theory calculations clarified that the reaction pathway mediated by the cationic complex is more favorable than that mediated by the neutral complex by 1.0 kcal mol-1. We further found that the flexible ligand exchange between Ca and Co ions is important for the alternating copolymerization to proceed smoothly.

Development of a novel sialic acid-conjugated camptothecin prodrug for enhanced cancer chemotherapy.

Camptothecin (CPT) is an attractive natural drug for cancer chemotherapy. However, the poor water solubility, non-targeting feature, and adverse side effects of CPT are significant obstacles to developing an effective anticancer drug. Here, for the first time, 9-thiol-sialic acid (9-SH-Sia) is coupled to CPT by forming a disulfide releasable carbonate linkage, resulting in a novel CPT prodrug (CPT-ss-Sia) that self-assembles into nanostructures in an aqueous solution. Strikingly, CPT-ss-Sia exhibited excellent in vitro properties, including enhanced water solubility, glutathione (GSH)-triggered CPT release, and increased E-lactone ring stability. Furthermore, CPT-ss-Sia had good cancer cell-killing ability comparable to CPT. Intravenous administration of CPT-ss-Sia significantly inhibited the growth of multiple types of tumors. Histological analysis showed that CPT-ss-Sia treatment significantly reduced lesions in tumor-bearing mice compared to CPT treatment. Notably, CPT-ss-Sia treatment did not adversely affect the body weight of the mice. This is the first report of the 9-SH-Sia conjugate-based prodrug. Overall, CPT-ss-Sia has broad clinical application prospects.

Rapid screening of unprecedented sesquiterpenes with distinctive ring skeletons from Daphne aurantiaca employing an integrated strategy

Unprecedented sesquiterpenoid scaffolds, furnished by unexpected carbon–carbon linkage formation or cleavage, were targeted and isolated from Daphne aurantiaca following an integrated strategy.

How graphenic are graphynes? Evidence for low-lying correlated gapped states in graphynes.

Graphynes can be structurally envisioned as 2D extensions to graphene, whereby linearly bonded carbon linkages increase the distance between trigonal carbon nodes. Many graphynes have been predicted to exhibit a Dirac-like semimetallic (SEM) graphenic electronic structure, which could potentially make them competitive with graphene for applications. Currently, most graphynes remain as attractive synthetic targets, and their properties are still unconfirmed. Here, we demonstrate that the electronic structure of hexagonal α-graphyne is analogous to that of biaxially strained graphene. By comparison with accurate quantum Monte Carlo results on strained graphene, we show that the relative energetic stability of electronic states in this correlated 2D system can be captured by density functional theory (DFT) calculations using carefully tailored hybrid functionals. Our tuned hybrid DFT approach confirms that α-graphyne has a low energy correlated Mott-like antiferromagnetic insulating (AFI) state, which competes with the SEM state. Our work shows that the AFI-SEM crossover in α-graphyne could be tunable by in-plane biaxial strain. Applying our approach to other graphynes shows that they should also exhibit correlated AFI states, which could be dominant even at zero strain. Calculations using an onsite Coulombic repulsive term (i.e., DFT + U) also confirm the predictions of our hybrid DFT calculations. Overall, our work strongly suggests that graphynes are not as graphenic (i.e., Dirac-like) as often previously predicted by DFT calculations using standard generalized gradient approximation functionals. However, due to the greater electronic versatility (e.g., tunable semiconducting bandgaps and accessible spin polarized states) implied by our study, graphynes could have novel device applications that are complementary to those of graphene.

Copolymerization of Carbonyl Sulfide and Propylene Oxide via a Heterogeneous Prussian Blue Analogue Catalyst with High Productivity and Selectivity.

This study demonstrates the superiority of a stable and well-defined heterogeneous cobalt hexacyanocobaltate (Co3 [Co(CN)6 ]2 ), a typical cobalt Prussian Blue Analogue (CoCo-PBA) that catalyzes the copolymerization of carbonyl sulfide (COS) and propylene oxide (PO) to produce poly(propylene monothiocarbonate)s (PPMTC). The number-average molecular weights of the PPMTC were 66.4 to 139.4 kg/mol, with a polydispersity of 2.0-3.9. The catalyst productivity reached 1040 g polymer/g catalyst (12.0 h). The oxygen-sulfur exchange reaction (O/S ER), which would generate random thiocarbonate and carbonate units, was effectively suppressed, and thus the selectivity of the monothiocarbonate over carbonate linkages was up to >99%. It was shown that no cyclic thiocarbonate byproduct was produced during the heterogeneous catalysis of COS/PO copolymerization using CoCo-PBA as the catalyst. The content of monothiocarbonate and ether units in the copolymer chain could be regulated by tuning the feeding amount of COS.

Identifying channels of environmental impacts of transport sector through sectoral linkage analysis

Considering sectoral linkages with the transport sector during the process of its low-carbon transition is critical for meeting the emission reduction targets of the whole economy. However, the precise roles of different transport modals and their sectoral linkages and transfer mechanisms in driving carbon dioxide (CO2) emissions are unknown. This study proposes a framework integrating the hypothetical extraction method (HEM) and structural path analysis (SPA) to explore the CO2 emission characteristics of the transport sector. Based on the above framework, we not only identify the emission sources and destinations related to various transport sub-sectors, but also reveal key channels through which emissions are transmitted along the economic network. Taking China as an example, we find there are heterogeneous characteristics of CO2 emissions in different transport modals, in which the railway passenger transport sector and the water passenger transport sector are CO2 emissions importers while other transport sub-sectors are CO2 emissions exporters. Furthermore, the transport sector mainly exports CO2 emissions to the construction and service sectors and imports emissions from electricity and heat production and supply sector. From the perspective of transfer paths in forward linkages, the main intermediate sectors of passenger transport sectors are service sectors, while those of freight transport sectors are construction sectors. From the perspective of transfer paths in backward linkages, electricity and heat production and supply sector is the main emission source and intermediate sector. When developing sector-specific and supply chain-wide low-carbon policies, it is suggested to consider the sectoral carbon linkages of each transport sub-sector.

Alternating copolymerization of carbon dioxide with alicyclic epoxides using bimetallic nickel(II) complex catalysts containing benzotriazole-based salen-type derivatives: Catalysis and kinetics

A series of dinuclear nickel complexes based on hexadentate bis(benzotriazole iminophenolate) derivatives with the 1,4-butylene diimine bridging backbone have been synthesized and characterized by single crystal x-ray crystallography. Dinickel complex 1 was demonstrated to be an efficient catalyst for alternating copolymerization of carbon dioxide (CO2) with cyclohexene oxide (CHO) or 4-vinyl-1,2-cyclohexene oxide (VCHO), affording CO2-based polycarbonates with >99% carbonate linkages under the optimized conditions. Particularly, not only the effective catalytic property of binickel complex 1 for CO2-copolymerization of alicyclic epoxides is enabled, but also 1 has been demonstrated to reveal an “immortal” manner in the CO2/VCHO copolymerization. Using the dinickel catalyst 1 in combination with excess diol derivatives as the chain transfer agents could produce very narrowly distributed poly(vinylcyclohexene carbonate) polyols having molecular weights ranging from 5000 to 12000 g/mol. In addition, detailed kinetic studies of the CO2/CHO copolymerization by Ni catalyst 1 were investigated. The results showed that such copolymerization follows a first-order kinetics on both catalyst 1 and CHO concentrations.

Modelling Structural Effect and Linkage on Carbon Emissions in China: An Environmentally Extended Semi-Closed Ghosh Input–Output Model

The carbon emissions of sectors and households enabled by primary inputs have practical significance in reality. Considering the mutual effect between the industrial sector and the household, this paper firstly constructed an environmentally extended semi-closed Ghosh input–output model with an endogenized household sector to analyze the relationship between carbon emissions and the Chinese economy from the supply-side perspective. The structural decomposition analysis and the hypothetical extraction method were remodified to identify the supply-side driving effects of the changes in carbon emissions and investigate the net carbon linkage. The results show that the electricity, gas, and water supply sector was the key sector with the highest carbon emission intensity enabled by primary inputs. The household sector had an above 93% indirect effect of the enabled intensity, with its enabled intensity dropping significantly by more than 55% from 2007 to 2017. The operating surplus and mixed income caused 3214.67 Gt (34.17%) of the enabled emissions in 2017. The supply-side economic activity, measured by the value added per capita, was the main factor of the carbon emission growth, mainly attributed to the development of the manufacturing sector and the electricity, gas, and water supply sector. The emission intensity and allocation structure both brought a decrease in carbon emissions. The electricity, gas, and water supply sector and the manufacturing sector were the major sources of the supply-induced cross-sectoral input emissions, while the commercial and service sector and the household sector were the top source of supply-induced cross-sectoral output emissions. This paper sheds light on the policies of the carbon emission abatement and the adjustment of the allocation structure from the perspective of supply.

AIEgen-Terminated Charge-Switchable Zwitterionic Azo Polymer for Tumor Hypoxia Imaging

For fluorescent probes, getting over the obstacles encountered in an organism is an important prerequisite. A zwitterionic to cationic polymer is an attractive approach to realize long-term circulation and high cellular uptake efficiency at the same time. Here, we reported a hypoxia-activatable zwitterionic to cationic azo polymer for tumor imaging, which was composed of an AIEgen-decorated RAFT agent and an azo monomer unit with a carbonate linkage. The zwitterion group endowed it with great anti-fouling property, avoiding being captured by proteins in the blood stream. Under the hypoxic microenvironment, the azo bond was broken and changed into amine with positive charge, which enhanced the cellular uptake efficiency. Meanwhile, the fluorescence quenching effect was cut off because of the destruction of the azo units. Therefore, the probe achieved a “turn-on” process and could be used as a fluorescent probe for tumor hypoxia imaging.

Fabrication and analysis of barium-based metal organic framework characteristic properties

Metal Organic framework (MOFs) a diverse class of complex organic metal assemblages has been attracting a great interest due to its easy tunability and modified characteristics during the past few years. These nanoscale-to-microscale-sized structures have been employed in different applicative fields due to their striking functional chemistry. Barium MOF synthesis is based on barium metal ions tri-linked organically to form a cubic structure and features photolumincity. Ba-MOF was synthesized by hydrothermal method and structural and optical analysis was performed using X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Raman Spectroscopy and Zeta Potential. The presence of cubic structure and organic carbon and oxygen linkages was indicated by XRD peaks. EDS directs the presence of barium as well as carbon and oxygen (organic linkers). Raman analysis paid for witnessing the evidence of the synthesis of MOF structure by validating the peak location. The photoluminescence spectrum was applied to measure the bandwidth to study the photoluminescence characteristics. The PL spectrum presented a wide bandwidth of 107.4 nm indicating Ba-MOF to be an efficient photoluminescent nanocomposite for photoluminescence-based applications. Zeta potential value of [Formula: see text] mV characterized anionic behavior and high stability of fabricated Ba-MOF.