Volume 91, Issue 3

Catechol moiety offers a versatile platform in the preparation of functionalized polymers, but it is not usually compatible with catalysis in polymerizations. To address these challenges, we suggest employment of one Brønsted base in masking the activity of catechol moiety and to modulate the polymerization. Based on this strategy, the ring-opening polymerization (ROP) of sarcosine N -carboxyanhydrides (Sar-NCA) was carried out using dopamine hydrochloride as an initiator and triethylamine as a Brønsted base. PSar with predicted molecular weights ( M n,NMR =3.7 kg mol −1 ) and narrow dispersities ( Đ <1.13) was prepared. Catechol initiator was successfully linked to PSar end as confirmed by MALDI-ToF MS. Subsequently, copolymerization of N -butyl glycine N -carboxyanhydrides (Bu-Gly-NCA) from the PSar in one-pot produced catechol end-functionalized amphiphilic polysarcosine- block -poly( N -butyl glycine) diblock copolypeptoids (cat-PSar- b -PGly Bu ). Further, cat-PSar- b -PGly Bu enabled the aqueous dispersion of manganese oxide nanoparticles which was attributable to the anchor of the diblock copolymers onto the surface of the nanoparticles. The strategy for catechol masking and polymerization mediating by one Brønsted base offered a new avenue into the synthesis of catechol-ended block copolymers.

Water represents an essential resource for life and for all natural processes. Our existence and our economic activities are totally dependent on this precious resource. It is well known that into the developing countries the main resource of drinkable water is represented by underground waters, so their contamination with arsenic represents a real problem that needs to be solved. To solve the problem of arsenic water pollution, it was necessary to develop a series of chemical, physicochemical and biological methods to reduce arsenic concentrations from water. From all these methods, adsorption offers many advantages including simple and stable operation, easy handling of waste, absence of added reagents, compact facilities and generally lower operation cost. The goal of this paper is to study the sorption properties of a new adsorbent material prepared by impregnating Amberlite XAD7 resin with crown ether (dibenzo-18-crown-6 ether) and loaded with Fe(III) ions. Solvent impregnated resin (SIR) method was used for functionalization. Amberlite XAD7 resin functionalization was evidenced by energy dispersive X-ray analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis and determination of specific surface by the Brunauer, Emmett and Teller (BET) analysis. Equilibrium, kinetic and thermodynamic studies were performed in order to determine the removal efficiency of the studied adsorbent for arsenic removal from water. In order to study the As(V) adsorption mechanism the experimental data were modelled using pseudo-first-order and pseudo-second order kinetic models. Kinetic of adsorption process was better described by pseudo-second-order model. Experimental data were fitted with three non-linear adsorption isotherm models: Langmuir, Freundlich and Sips. Obtained experimental data were better fitted by Sips adsorption isotherm. The values of thermodynamic parameters (Δ G °, Δ H °, Δ S °) showed that the adsorption process was endothermic and spontaneous. The results proved that Amberlite XAD7 resin with crown ether and loaded with Fe(III) is an efficient adsorbent for the As(V) removal from water. The possibility of reuse the adsorbent material through adsorption and desorption cycles was also studied and it was found that the material can be used in five sorption-desorption cycles. Maximum adsorption capacity obtained experimentally being 18.8 μg As(V)/g material.

A series of renewable novel bicyclic AB type polyester precursors have been prepared in good overall yield from lignocellulosic biomass. These advancements take full advantage of the differing oxidation states of functional groups in 5-(hydroxymethyl)furfural by chemoselective preparation of furanic hydroxy esters and applying benzyne-Diels–Alder cycloaddition/aromatization strategies.

2,5-Furandicarboxylic acid and itaconic acid are both important biobased platform chemicals and their terpolymer with 1,6-hexanediol (HDO) can be the starting point for a new class of reactive polyesters, with important applications. The green synthetic route developed in this study involves a biocatalytic condensation polymerization reaction of dimethyl furan-2,5-dicarboxylate (DMFDC) and dimethyl itaconate (DMI) with HDO in toluene at 80°C, using commercial immobilized lipases from Candida antarctica B. In the best conditions, the formed polymer product was isolated with more than 80% yield, containing about 85% terpolymer with average molecular mass of about 1200 (M n , calculated from MALDI-TOF MS data) and 15% DMFDC_HDO copolymer. Considering the higher reactivity of DMFDC, the composition of the synthesized polymer can be directed by adjusting the molar ratio of DMFDC and DMI, as well as by extending the reaction time. Structural analysis by NMR demonstrated the regioselective preference for the carbonyl group from DMI adjacent to the methylene group. The biocatalyst was successfully reused in multiple reaction cycles.

The first step in obtaining of a specific polymer sorbent containing sulfur atoms was the synthesis of a functional monomer – 2,2′-thiobisethanol dimethacrylate (TEDM). Synthesis consists of the reaction of 2,2′-thiobisethanol with methacryloyl chloride in the presence of triethylamine in methylene chloride. The new poly(dimethacrylate)s materials containing sulfur atoms were synthesized in radical suspension polymerization. Homopolymerization of 2,2′-thiobisethanol dimethacrylate and its copolymerization with ethylene glycol dimethacrylate or pentaerythritol tetraacrylate were carried out. The selection of synthesis conditions determines the parameters of the polymer structure and its properties. The presence of sulfur atoms in polymer chains resulted in specific donor-acceptor interactions, which can intensify sorption ability towards metal ions belonging to the group of soft acids. Therefore, the sorption properties of the obtained materials have been determined based on the recovery of precious metal ions, such as gold(III) and silver(I).

(Poly)phosphonic acids constitute an exciting family of phosphorus compounds. One of the attractive attributes of these molecules is the rich chemistry of the phosphonate moiety, and, in particular, its high affinity for metal ions and mineral surfaces. Whether the phosphonate group belongs to a “small” molecule or to a polymeric matrix, phosphonate-containing compounds have found a phalanx of real-life applications. Herein, we address a special category of phosphorus compounds called bisphosphonates (BPs, a.k.a. “-dronates”) and also phosphonate containing polymers. The success of BPs in mitigating osteoporosis notwithstanding, these “-dronate” drugs present a number of challenges. Nevertheless, the main drawback of BPs is their limited oral bioavailability. It is, therefore, imperative to design and fabricate “smart” systems that allow controlled delivery of the active BP agent. Here, easy-to-prepare drug delivery systems are presented based on silica gels. These have been synthesized, characterized, and studied as hosts in the control release of several BP drugs. They exhibit variable release rates and final % release, depending on the nature of bisphosphonate (side-chain length, hydro-philicity/-phobicity, water-solubility), cations present, pH and temperature. These gels are robust, injectable, re-loadable and re-usable. Furthermore, alternative drug delivery systems are presented that are based on metal-organic frameworks (MOFs). In these biologically acceptable inorganic metal ions have been incorporated, together with BPs as the organic portion. These materials have been synthesized, characterized, and studied for the self-sacrificial release (by pH-driven dissolution) of the BP active ingredient. Several such materials were prepared with a variety of bisphosphonate drugs. They exhibit variable release rates and final % release, depending on the actual structure of the metal-bisphosphonate material. Lastly, we will present the use of phosphonate-grafted polymers as scale inhibitors for water treatment applications.

Phenolic compounds are produced in thermal cracking processes, drugs and herbicides synthesis and other industrial processes. Such compounds exhibit high toxicity for aquatic environment and for aquatic life. So, due to their high toxicity is important to treat waters with phenols content. For the treatment of waste waters containing phenols or phenolic compounds several unconventional methods are applied, such as: inverse osmosis, coagulation, solvent extraction, flotation–coagulation combined processes, adsorption, and anaerobic processes. From all used remediation processes adsorption has a higher applicability degree due to its main advantages: simplicity, ease of use and operation and high efficiency. Through time activated carbon and ashes were used as adsorbent materials for phenols remediation, but such materials present the main disadvantage of low regeneration degree. Thus, it is important to develop and use new adsorbents with higher regeneration degree and longer life time. Polymeric materials have been used for removal of organic compounds and/or metal ions from contaminated water due to their versatility in functionality, morphology and texture properties. Chemical modification of polymeric matrices with pendant functional groups is a valuable method used to improve the surface and interface chemistry of polymeric adsorbents, to achieve better adsorption performance and to design tailor-made adsorbents with respect to specific pollutants. In present study new adsorbent materials were obtained starting from chloromethylated styrene-divinylbenzene copolymers with different degrees of crosslinking (6.7%, 12% and respectively 15% DVB), functionalized by reaction with 3-hydroxibenzaldehyde. The polymeric intermediates were further modified by polymer-analogous reaction with iso-propylamine and diethylphosphite with the aim to improve their adsorptive properties. The obtained polymeric adsorbents were tested for remediation of waters containing phenol (P), 2,3-dimethylphenol (2,3-DMP) and 2,4,6-trimethyl-phenol (2,4,6-TMP). Based on obtained experimental data the adsorption mechanism, process kinetics and thermodynamics were studied.

High-molecular alginates were extracted from Djiboutian brown seaweeds, Sargassum sp. ( S ) and Turbinaria ( T ) and isolated as sodium salts in 31.0 and 42.7% yield by weight. 1 H NMR analysis of the uronic acid block-structure indicates mannuronic/guluronic M/G ratios of 0.49 and 3.0 for the alginates extracts, respectively. The resulting alginates were deposited onto native Aerosil 200 silica, amine-functionalized and carboxyl-functionalized silica particles to enhance the mechanical strength providing Alg.(T/S)+SiO 2 ) Alg.(T/S)+SiO 2 NH 2 ) and Alg.(T)+SiO 2 CO 2 H) composites. Taking Pb(II) as examples for toxic heavy metal ions, the effects of the pH, adsorption kinetics, and isotherms have been studied systematically. The best uptake achieved was 585 mg Pb 2+ ion/g using Alg.S+SiO 2 NH 2 . Furthermore, the Pb(II) ions were successfully desorbed in several cycles from Alg.T+SiO 2 using 0.5 M hydrochloric acid. Therefore, Alg.T+SiO 2 may be considered as a low-cost biosorbent that quickly adsorbs and easily desorbs analyte lead ions. A comparison of the adsorption capacity of our biopolymer-coated particles with that of other adsorbents reported in the literature reveals that our materials are among the best performing for the adsorption of Pb(II).

Polar semiconducting polymers based on a conjugated polymer backbone endowed with chemically anchored polar groups on the side chains have proved to be particularly interesting as optimization layer at organic/cathode interface in optoelectronic devices. In particular, the pendant phosphonate groups impart water-alcohol solubility allowing easy solution processing, and improve electron injection thanks to both a favorable interfacial dipole of phosphonate groups and an intense coordination interaction between the phosphonate groups and Al cathode. In this work we synthesize alternating fluorene-benzothiadiazole copolymers by proposing a post-polymerization reaction to insert the phosphonate groups. Thanks to this approach it is possible to use standard Suzuki coupling conditions, simplifying the process of synthesis, purification and characterization. The polymer Poly[9,9-bis(6′-diethoxylphosphorylhexyl)-alt-benzothiadiazole] (P2), is tested in conventional organic solar cells as cathode interfacial layers showing, with respect to the control device, an increasing of all the photovoltaic parameters, with a final power conversion efficiency that reaches 5.35% starting from 4.6%. The same trend is observed for multilayered polymer light-emitting diodes with an external quantum efficiency of the P2-based PLED enhanced of 1.5 times with respect to the basic devices with bare Al cathode, and negligible roll-off efficiency. The synergic effects of energy gap modulation and of polar phosphonated pendant functionalities of P2 are compared with the corresponding fluorene-based polar homopolymer. Our results show that, not only a proper selection of side functionalities, but also the tailoring of the energy gap of cathode interfacial materials (CIMs) is a possible effective strategy to engineer cathode of different optoelectronic devices and enhance their performance.

N , N , N -Trimethylchitosan (TMC) represents a rare example of cationic polysaccharides and numerous studies have shown its potential in biological and biomedical applications. TMC with high degrees of quaternization (DQ) were synthesized from N -methylation of N , N -dimethylchitosan (DMC), which was obtained by reductive alkylation of high molecular weight chitosan in a simple step process and in good yields. The effects of base and solvents were evaluated on the quaternization reaction. The N -methylation of DMC was performed selectively by CH 3 I and carbonate in water where quaternization was achieved quantitatively with a low degree of O -methylation (17 %). Moreover, the greener procedure allows easy recovery and purification by conventional filtration as a carbonate salt, in which the anion can be exchanged by an acid-base reaction. Quantification of DQ involving 1 H NMR integration of methyl peaks must be performed on protonated TMC. High field NMR spectra of TMC showed two specific chemical shifts for anomeric peaks (5.0 and 5.4 ppm) that can also be used for the determination of DQ. This latter method avoids the superimposition problems with other pyranosyl peaks.

In this paper, the synthesis of terpolymers bearing carbazole, coumarin and 8-hydroxyquinoline moiety as pendant groups with content of coumarin and 8-hydroxyquinoline between 0.5 and 4 mol% was elaborated. Then the terpolymers underwent complexation reactions with aluminum bis(8-hydroxyquinoline)isopropoxylate (Alq 2 ispr) to form polymeric hybrid materials with aluminum tris(8-hydroxyquinoline) (Alq3) as side groups. The presence of carbazole, coumarin (MK) and 8-hydroxyquinoline (QM) as well as Alq3 in the terpolymers was confirmed by NMR, UV, photoluminescence, and size exclusion chromatography. The results indicates that these hybrid polymers have moderate molecular weights and solubility in common organic solvents. For photoluminescence spectra, an evidence for energy transfer from carbazole to coumarin and Alq3 groups was observed and highest relative fluorescence intensity was exhibited by solutions of the terpolymers containing the lowest content of MK, QM and Alq3.

Two grades of chitosan [chitosan 30000 g mol −1 (N-chitosan 30) and 250000 g mol −1 (N-chitosan 250)] were functionalized by the Kabachnik–Fields reaction. To obtain the highest phosphonic ester grafting rate (55% and 40% for the N-chitosan 30 and N-chitosan 250, respectively), the pH must be kept constant during the reaction (pH=5). Then, a partial hydrolysis of the ester functions was carried out in HCl medium to generate phosphonic acid functions up to 25% and 20% for the N-chitosan 30 and N-chitosan 250, respectively. It was shown that the grafting of phosphonic acids on chitosan significantly reduced the dynamic viscosity. Afterwards, electrochemical impedance measurements were performed in an aqueous solution (pH=5) in the presence of either N-chitosans or P-chitosans (3 wt.%). The two native N-chitosans were little adsorbed onto the carbon steel surface and the corrosion protection was low. In contrast, the impedance results in the presence of the 30000 g mol −1 phosphorylated chitosan (P-chitosan 30) evidenced the beneficial effect of grafted phosphonic acid on its adsorption on the steel surface. The lower efficiency of the 250000 g mol −1 (P-chitosan 250) was attributed to its high molecular weight which made difficult the interactions between the phosphonic groups and the metallic surface.

The present document provides recommendations for (i) definitions of terms related to dendrimers with regular dendrons and to hyperbranched polymers, and (ii) nomenclature for naming these complex compounds on the basis of structure-based nomenclature for regular and irregular organic polymers, including adjustments required for specifying dendritic and hyperbranched macromolecular structures. The recommendations and the examples deal with organic-chemical structures only. Nevertheless, the general principles described in this document can similarly be applied to inorganic and to hybrid inorganic-organic dendrimers and hyperbranched macromolecules.