Synthesis and Selective Au(III) Adsorption of Ureido Polymers Containing Large Repeating Rings
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ABSTRACT:
SUBMITTER: Sun Y
PROVIDER: S-EPMC8552319 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A scaling theory is developed for selective adsorption of polymers induced by the strong binding between specific monomers and complementary surface adsorption sites. By "selective" we mean specific attraction between a subset of all monomers, called "sticky", and a subset of surface sites, called "adsorption sites". We demonstrate that, in addition to the expected dependence on the polymer volume fraction ϕbulk in the bulk solution, selective adsorption strongly depends on the ratio between two characteristic length scales, the root-mean-square distance l between neighboring sticky monomers along the polymer, and the average distance d between neighboring surface adsorption sites. The role of the ratio l/d arises from the fact that a polymer needs to deform to enable the spatial commensurability between its sticky monomers and the surface adsorption sites for selective adsorption. We study strong selective adsorption of both telechelic polymers with two end monomers being sticky and multisticker polymers with many sticky monomers between sticky ends. For telechelic polymers, we identify four adsorption regimes at l/d < 1 that are characterized by the fraction of occupied adsorption sites and whether the dominant conformation of adsorbed chains is a single-end-adsorbed "mushroom" or double-end-adsorbed loop. For l/d > 1, we expect that the adsorption layer at exponentially low ϕbulk consists of separated unstretched loops, while as ϕbulk increases the layer crosses over to a brush of extended loops with a second layer of weakly overlapping tails. For multisticker chains, in the limit of exponentially low ϕbulk, adsorbed polymers are well separated from each other. As l/d increases, the conformation of an individual polymer changes from a single-end-adsorbed "mushroom" to a random walk of loops. For high ϕbulk, adsorbed polymers at small l/d are mushrooms that cover all the adsorption sites. At sufficiently large l/d, adsorbed multisticker polymers strongly overlap. We anticipate the formation of a self-similar carpet and with increasing l/d a two-layer structure with a brush of loops covered by a self-similar carpet. As l/d exceeds the threshold determined by the adsorption energy, the brush of loops under the carpet reaches a saturated state, resulting in a l/d-independent brush-under-carpet structure, which can also be applied to describe adsorbed multisticker polymers in nonselective adsorption where a sticker can strongly bind to any place on the adsorption surface. We examine the adsorbed amount Γ of multisticker polymers in different regimes for selective adsorption. If the adsorbed multisticker polymers are nonoverlapping mushrooms, the adsorbed amount Γ increases linearly with the surface density of adsorption sites Σ ≈ 1/d2. In the self-similar carpet regime, Γ increases sublinearly as Σ0.15 in a good solvent, while only logarithmically in a theta solvent. Formation of a brush layer under the carpet contributes an additional adsorbed amount. This additional amount increases linearly with Σ and eventually dominates the overall adsorbed amount Γ before saturating at a plateau value controlled by the adsorption energy.
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Project description:An iron(III) complex of tetradentate N,N'-disubstituted bis(aminophenoxide) (designated as salan, a saturated version of the corresponding salen ligand) with a sterically hindered organic base anchored on the ligand framework, can selectively mediate the conversion of carbonyl sulfide to sulfur-containing polymers by the copolymerization with epoxides. This single-site catalyst exhibits broad substrate scope, and the resultant copolymers have completely alternating structures. In addition, this catalyst is efficient in producing diblock copolymers, suggesting a living polymerization nature.
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Project description:In this research, a novel, sulfamethazine, thermosensitive, molecularly-imprinted polymer (MIP) with an obvious core?shell structure for the enrichment of sulfamethazine (SMZ), which involved temperature sensitive monomer N-Isopropylacrylamide, functional monomer methacrylic acid and cross-linking agents ethyleneglycol dimethacrylate (EGDMA) and N,N'-methylenebisacrylamide, was successfully compounded using the surface polymerization method. To ensure the best experimental group, we designed and compared three groups of controlled experiments of MIPs with different crosslinking agents. When the adsorption temperature was almost the lower critical solution temperature (LCST) of Poly(N-Isopropylacrylamide), the preparative MIPs showed outstanding adsorption capacity and specific identification to sulfamethazine. Moreover, this allowed the MIPs to better facilitate by combining the template molecules, as well as optimizing the imprinting factor. In addition, after 80 min, the adsorption of the MIPs leveled off and remained constant, and the adsorption quantity reached (a maximum of) at 8.1 mg·g-1.
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Project description:A series of ethylenediamine-grafted ion imprinted magnetic polymers (Fe3O4@IIPs) were synthesized via ultrasonic assisted suspension polymerization with perchlorate (ClO4 -) as an ion imprinting template. They were characterized by XRD, EA, VSM, FTIR and XPS and applied as adsorbents for ClO4 - removal from aqueous solutions. The effects of the usage amount of crosslinking agent divinylbenzene (DVB) used for preparation on the structure and the adsorptive performance of Fe3O4@IIPs were investigated. The results show that the Fe3O4@IIPs have an average size of 200-800 nm, which increases with the increase of the amount of DVB from 0 to 2 g during the preparation process. The saturation magnetization intensities are at 35.6-42.8 emu g-1, which decrease with the increase of the usage amount of DVB. The addition of DVB is beneficial to the formation and stability of the ion imprinted cavity of Fe3O4@IIPs. The effects of the solution pH value, initial concentration of ClO4 -, and adsorption time on the adsorption properties of ClO4 - in aqueous solutions were investigated. The results show that the adsorption capability is affected significantly by solution pH value and reaches the maximum adsorption capacity at pH 3.0. The best adsorption capacity and selectivity of Fe3O4@IIPs to ClO4 - can be obtained when the usage amount of DVB is at 0.5 g for synthesis. The adsorption mechanisms might include both ion exchange and electrostatic interaction. The isothermal adsorption curves mainly obey the Langmuir model with the theoretical maximum adsorption capacities (q m,c) at 76.92-111.1 mg g-1 and the experimental maximum adsorption capacities (q m,e) at 75.7-108.9 mg g-1, respectively, which are much higher than those of the non-ion imprinted material (Fe3O4@NIP, q m,NIP: q m,c at 60.61 mg g-1 and q m,e at 59.0 mg g-1). The adsorption kinetic studies show that the adsorption processes reach equilibrium within 10 min and the kinetic data are well fitted to the pseudo-second-order model. There is almost no interference by the coexisting anions for the selective adsorption of ClO4 -, with a imprinting factor (α) at 1.8, and selectivity factor (β) larger than 5.9 for several kinds of common co-existing anions, respectively. The Fe3O4@IIPs are ideal candidates for removal of ClO4 - from aqueous solution.
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Project description:The adsorption isotherms, kinetics, and thermodynamics of fluoride ions (F-) on FeOOH powders in water were investigated to obtain fundamental information on FeOOH powders, which are used as F- adsorbents in drinking and industrial water, and industrial wastewater. FeOOH powders were prepared as precipitates by mixing aqueous FeCl3 and NaOH solutions (1:3 mol/mol) in the presence of 2,2,6,6,-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized cellulose nanofibrils (TOCNs), carboxymethylcellulose (CMC), or TEMPO-oxidized cellulose (TOC) fibers (without nanofibrillation), and subsequent drying and pulverizing. The FeOOH:TOCN, FeOOH:CMC, and FeOOH:TOC dry mass ratios were controlled at 87:13. The amount of F- adsorbed by the FeOOH/TOCN powder per FeOOH mass was higher than those adsorbed by FeOOH, FeOOH/CMC, or FeOOH/TOC. The F- adsorption isotherms on the FeOOH-containing powders showed higher correlation coefficients with the Langmuir model than with the Freundlich model. This indicates that F- adsorbed on FeOOH initially formed a monolayer, predominantly via physical adsorption. Pseudo-second-order kinetics fitted well to the time-dependent F- adsorption behaviors on the FeOOH-containing powders. Thermodynamic analysis of F- adsorption on the FeOOH-containing powders showed that the ΔG values were negative, which indicates that F- adsorption on the FeOOH-containing powders proceeded spontaneously in water. The negative ΔG value for FeOOH/TOCN was higher than those for FeOOH, FeOOH/CMC, and FeOOH/TOC at the same temperature. This shows that the FeOOH/TOCN powder can be used as an excellent and efficient F- adsorbent in water.
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Project description:Five new pyran rings containing polyketides, penicipyrans A-E (1-5), together with the known pestapyrone A (6), were isolated from the saline soil-derived Penicillium raistrickii. Their structures were determined by interpretation of NMR and HRESIMS data. The absolute configurations of compounds 4 and 5 were established by the modified Mosher's method and single-crystal X-ray diffraction analysis, respectively. These compounds possessed high structural diversity including two α-pyrones (1, 2), three isocoumarins (3, 4, 6), and one dihydropyran derivative (5). Among them, Compound 5 exhibited cytotoxicity against HL-60 and K562 cell lines with IC50 values of 4.4 and 8.5 μM, respectively.
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Project description:We examined the surface structure, binding conditions, electrochemical behavior, and thermal stability of self-assembled monolayers (SAMs) on Au(111) formed by N-(2-mercaptoethyl)heptanamide (MEHA) containing an amide group in an inner alkyl chain using scanning tunneling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and cyclic voltammetry (CV) to understand the effects of an internal amide group as a function of deposition time. The STM study clearly showed that the structural transitions of MEHA SAMs on Au(111) occurred from the liquid phase to the formation of a closely packed and well-ordered β-phase via a loosely packed α-phase as an intermediate phase, depending on the deposition time. XPS measurements showed that the relative peak intensities of chemisorbed sulfur against Au 4f for MEHA SAMs formed after deposition for 1 min, 10 min, and 1 h were calculated to be 0.0022, 0.0068, and 0.0070, respectively. Based on the STM and XPS results, it is expected that the formation of a well-ordered β-phase is due to an increased adsorption of chemisorbed sulfur and the structural rearrangement of molecular backbones to maximize lateral interactions resulting from a longer deposition period of 1 h. CV measurements showed a significant difference in the electrochemical behavior of MEHA and decanethiol (DT) SAMs as a result of the presence of an internal amide group in the MEHA SAMs. Herein, we report the first high-resolution STM image of well-ordered MEHA SAMs on Au(111) with a (3 × 2√3) superlattice (β-phase). We also found that amide-containing MEHA SAMs were thermally much more stable than DT SAMs due to the formation of internal hydrogen networks in MEHA SAMs. Our molecular-scale STM results provide new insight into the growth process, surface structure, and thermal stability of amide-containing alkanethiols on Au(111).
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Project description:The first zeolite structure (ITQ-40) that contains double four (D4) and double three (D3) member ring secondary building units has been synthesized by introducing Ge and NH(4)F and working in concentrated synthesis gels. It is the first time that D3-Rs have been observed in a zeolite structure. As was previously analyzed [Brunner GO, Meier, WM (1989) Nature 337:146-147], such a structure has a very low framework density (10.1 T/1,000 A(3)). Indeed, ITQ-40 has the lowest framework density ever achieved in oxygen-containing zeolites. Furthermore, it contains large pore openings, i.e., 15-member rings parallel to the [001] hexagonal axis and 16-member ring channels perpendicular to this axis. The results presented here push ahead the possibilities of zeolites for uses in electronics, control delivery of drugs and chemicals, as well as for catalysis.
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Project description:An efficient method for the asymmetric gold(I)-catalyzed preparation of medium sized rings has been developed. The method provides 7- to 9-membered rings in excellent yield. High enantioselectivities can be achieved for 7- and 8-membered ring products employing chiral gold(I) complexes. The results provide insight into the mechanism, showing the fluxional nature of gold(I)-stabilized vinyl carbenoid intermediates.
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Project description:Antimony(III) is a rare element whose chemical and toxicological properties bear a resemblance to those of arsenic. As a result, the presence of Sb(III) in water might have adverse effects on human health and aquatic life. However, Sb(III) exists at very ultra-trace levels which may be difficult for direct quantification. Therefore, there is a need to develop efficient and reliable selective extraction and preconcentration of Sb(III) in water systems. Herein, a selective extraction and preconcentration of trace Sb(III) from environmental samples was achieved using ultrasound assisted magnetic solid-phase extraction (UA-MSPE) based on magnetic Sb(III) ion imprinted polymer-Fe3O4@SiO2@CNFs nanocomposite as an adsorbent. The amount of antimony in samples was determined using inductively coupled plasma optical emission spectrometry (ICP-OES). The UA-MSPE conditions were investigated using fractional factorial design and response surface methodology based on central composite design. The Sb(III)-IIP sorbent displayed excellent selectivity towards Sb(III) as compared to NIIP adsorbent. Under optimised conditions, the enrichment factor, limit of detection (LOD) and limit of quantification (LOQ) of UA-MSPE/ICP-OES for Sb(III) were 71.3, 0.13 µg L-1 and 0.44 µg L-1, respectively. The intra-day and inter-day precision expressed as relative standard deviations (%RSDs, n = 10 and n = 5) were 2.4 and 4.7, respectively. The proposed analytical method was applied in the determination of trace Sb(III) in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95-98.3%.
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