Cationic-modified cyclodextrin nanosphere/anionic polymer as flocculation/sorption systems

Simultaneous removal of dissolved and colloidal substances has been a challenging task. The cationic-modified beta-cyclodextrin nanospheres synthesized in this work, in conjunction with a water-soluble polyacrylamide-based anionic polymer, potentially provide a novel approach to address the problem. The cyclodextrin was rendered cationic using (2,3-epoxypropyl)trimethylammonium chloride as a reagent. The cationicity of the modified cyclodextrin and the reaction between cyclodextrin and the reagent were characterized by electrophoresis measurement, polyelectrolyte titration, and NMR. As a dual-component flocculation system, the cationic cyclodextrin/anionic polymer significantly induced clay flocculation, lowering the relative turbidity of the clay suspension over a wide pH range. Meanwhile, as a nanospherical absorbent, the modified cyclodextrins exhibited strong affinity toward aromatic compounds via inclusion complex formation in the hydrophobic cavities, which was monitored by UV spectroscopy. These systems facilitated the simultaneous removal of dissolved and colloidal substances, which was unachievable previously. In addition, the interaction between anionic polymers and the clay particles pretreated with cationic cyclodextrin was investigated in order to reveal the flocculation mechanism.     

Tuning the interactions in cyclodextrin polymer nanoassemblies

The aim of this paper was to study the associations between a neutral β-cyclodextrin polymer and amphiphilic dextrans substituted with two kinds of groups able to make inclusion complexes with β-cyclodextrin. The first kind of substituent is purely hydrophobic (dodecyl C₁₂ or adamantyl Ada groups) and the second one, cyclohexancarboxylic acid group CHX, brings pH-dependent charge density on the dextran chains. Synthesis and characterization of the di-substituted dextrans have been detailed in a first part where it has been shown that the incorporation of CHX groups (up to 7 mol.%) did not modify the self assembling properties of the amphiphilic dextrans. Affinity of the amphiphilic dextrans for β-cyclodextrin polymer has been studied by different methods including isothermal titration calorimetry, dynamic light scattering and zeta potential. An original pH sensitive behaviour has been obtained for polymer–polymer associations at low concentrations. Nanoassemblies are formed at pH around 4 which are destabilized at lower pH and swollen into soluble aggregates at higher pH. The nanoassemblies formed at pH 4 have also been evidenced by transmission electron microscopy and have revealed a spherical shape of few hundred nanometers.     

Stretching a polymer brush by making in situ cyclodextrin inclusion complexes

The interaction between poly(ethylene oxide) (PEO) chains grafted onto polystyrene latex particles and alpha-, beta-, and gamma-cyclodextrins (CD) was studied by small-angle neutron scattering. The particles were contrast-matched to the solvent in order that only the scattering from the polymer layers was detected. The signal from the layers was fitted to a double-exponential volume fraction profile. The effects of adding cyclodextrin on the polymer profile are shown as a function of cyclodextrin concentration. The polymer layers are seen to extend on addition of CD, which is consistent with a complexation between the grafted PEO and the CD molecules. The effect is the strongest with alpha-CD.     

Palladated cyclodextrin and halloysite containing polymer and its carbonized form as efficient hydrogenation catalysts

β‐Cyclodextrin (β‐CD) and glycidyl methacrylate monomer were polymerized in the presence of functionalized halloysite nanoclay (Hal) to afford a polymeric network (Hal‐P‐CD) containing Hal and CD. Hal‐P‐CD was then applied as a catalyst support for the immobilization of Pd nanoparticles. The resulting nanocomposite, Pd@Hal‐P‐CD, could serve as a catalyst for the hydrogenation of nitrobenzene. The precise study by the preparation of control samples confirmed the contribution of CD as both phase transfer and capping agent, P (polymer) and Hal to the catalysis. Moreover, the results confirmed the importance of CD: glycidyl methacrylate monomer ratio. Pd@Hal‐P‐CD was also carbonized to prepare Pd@Hal‐C. Notably, the characterization of Pd@Hal‐C showed that carbonization led to the growth of mean diameter of Pd nanoparticles, increase of Pd content and partial destruction of Hal. However, the catalytic activity of Pd@Hal‐C was superior to Pd@Hal‐P‐CD. Pd@Hal‐C was also highly recyclable and could be recovered and recycled for several reaction runs. The study of the carbonization temperature showed that this factor affected the nature of the resulting carbon and the catalyst prepared at elevated temperature showed higher catalytic activity.     

Stimuli-responsive polymer hydrogels as a new class of draw agent for forward osmosis desalination

Ionic polymer hydrogels with thermal responsive units are found to induce higher water permeation rates in the osmosis process, and higher water release rates under a combination of pressure and thermal stimuli. These hydrogels have the potential for use as draw agent in forward osmosis desalination.     

Speed control for cyclodextrin rings on polymer chains

The inclusion of monomeric α,ω-diamines and related polymers by cyclodextrins was investigated by ¹H NMR spectroscopy. As a result we found, that for both monomers and polymers the rate of the inclusion process largely depends on the degree of protonation of the amino groups of the guest.     

Triazine interlinked covalent organic polymer as an efficient anti-bacterial agent

Herein, we report the synthesis of new covalent organic polymer comprising triazine and o-tolidine by solvothermal method. The formation of polymer was confirmed by Fourier transform infra red spectroscopy (FT-IR), cross polarization–magic angle spinning nuclear magnetic resonance (NMR), transmission electron microscopy, and scanning electron microscopy. Their antibacterial activity toward S. aureus (gram-positive) and P. aeruginosa (gram-negative) was assessed by the optical density measurements and direct contact method. These results have great significance toward the design of new porous polymers for antibacterial applications.     

Nanocellulose reinforced as green agent in polymer matrix composites applications

Owing to their abundance, high strength and stiffness, and low weight and biodegradability, nanocellulose (NC) is regarded as a promising candidate for the preparation of green composites. The high reinforcing effect assigned to the mechanical percolation phenomenon of NC is due to the stiff continuous networks of cellulosic nanoparticles linked via hydrogen bonding. Compared to nanocrystalline cellulose, NC fibers result in more significant improvement to the modulus, stiffness, and strength as aspect ratio NC fiber is higher compared to NC crystal. Indeed, in the case of biopolymer composites, the reinforcement effect of NC is attributed to the NC‐polymer interactions and the reinforcing effect occurring through effective stress transfer at the NC‐polymer interface. The NC‐reinforced composites tend to become more brittle as the concentration of the reinforcing particles increase up to the saturated level, due to the reduction in surface adhesion between filler and matrix. Due to its promising mechanical and structural stability, NC composites have been used widely in many industrial applications such as food packaging, electronic applications, and tissue engineering.     

Evaluation of a molecularly imprinted polymer as in-line concentrator in capillary electrophoresis

Molecularly imprinted polymers (MIPs) have been evaluated as sorbent for the construction of an in-line solid phase extraction concentrator in capillary electrophoresis to be applied in the monitoring of triazine herbicides: atrazine and its three metabolites, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Initially, the electrophoretic separation of these compounds was optimized. The electrolyte consists of an aqueous solution of 75 mM phosphoric acid (H(3)PO(4)) adjusted to pH 2.1 and containing 0.7 mM cetyltrimethylammonium bromide. After the fabrication and assembly of the concentrator into the capillary, these optimal CE conditions were applied to evaluate the performance of this device. Efficiencies of 40 000-55 000 plates could be achieved and the separation time was around one hour. Different parameters affecting the in-line molecularly imprinted solid-phase extraction in capillary electrophoresis such as composition and volume of the elution plug were optimized. The method was evaluated in terms of linearity, precision and limits of detection and quantification. MIPs were compared with Oasis hydrophilic-lipophilic-balance (HLB) particles for the in-line coupling of solid-phase extraction and capillary electrophoresis. The superior selectivity of MIPs is demonstrated through direct injection of a urine sample spiked with 10 microg/mL atrazine, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine. Recoveries were between 92 and 102% compared with an aqueous solution.     

Solubilization of itraconazole as a function of cyclodextrin structural space

Cyclodextrins are functional pharmaceutical excipients, which can dynamically include poorly water-soluble drugs and drug candidates resulting in improved solubility, stability and oral bioavailability. A number of formulations containing “natural” and chemically modified cyclodextrins have reached the market and are enjoying widespread attention and use. One such example is itraconazole, a broad-spectrum antifungal agent which is available in an aqueous hydroxypropyl-β-cyclodextrin (HPβCD) vehicle for both oral and parenteral use (Sporanox Oral Solution and Sporanox Intravenous Injection^®). While the interaction of itraconazole and HPβCD is well described, its ability to form complexes with other cyclodextrins is less understood. This creates an intriguing opportunity of screening the structural space of available cyclodextrin derivates by assessing their complexation with a single chemical probe, in this case itraconazole. To this end, a number of cyclodextrin derivatives were assess with regard to their ability to improve the water solubility of the test substrate. In some instances, more detail assessments including the effect of pH and the physical form of the drug probe were also completed. The various cyclodextrins solubilized itraconazole to varying extents (micrograms to milligrams) and by varying inclusion mechanisms and stoichiometries.     

Evaluation of 99mTc-ceftazidime as bacterial infection imaging agent

Although our understanding of microorganisms has advanced significantly and antimicrobial therapy has become increasingly available, infection remains a major cause of patient morbidity and mortality. The use of radiopharmaceuticals for diagnosis of infection is increasing due to their ability to distinguish between septic and aseptic inflammation. A wide range of radiopharmaceuticals have been proposed to visualize infection and inflammation scintigraphically. Ceftazidime a cephalosporin antibiotic used to treat bacterial infections was investigated to label with ^99mTc. Labeling was performed using sodium dithionite as reducing agent at 100 °C for 10 min and radiochemical analysis involved ITLC and HPLC methods. The stability of labeled antibiotic was checked in the presence of human serum at 37 °C up to 24 h. The maximum radiolabeling yield was 95.4 ± 2.0 % corresponding to a specific activity of 178 GBq/mmol. Bacterial binding assay was performed with S. aureus and the in vivo distribution was studied in mice. Images showed minimal accumulation in nontarget tissues, with an average target/nontarget ratio of % 1.4 ± 0.2.     

Evaluation of 99mTc-HIDA complex as a cholescintigraphic agent (author's transl)

In the reaction labeling N-(2,6-dimethylphenylcarbamoylmethyl) iminodiacetic acid (HIDA) with 99mTc, several complexes with different chemical characteristics were observed to occur with slight changes in the labeling conditions. Among these complexes, a complex detected in the bile of rats was limited to one complex, named as complex II. The preparation method of 99mTc-HIDA complex II and the exchange reaction between this complex and penicillamine indicate that 99mTc is coordinated with HIDA as low-hydrolyzed 99mTc in this complex. This complex is excreted rapidly through the bile and within 1 hr, about 65% of the total activity injected is recovered from bile in rats. The organ distribution of this complex was studied in mice by radioassay and in rabbits by scintillation camera and, in both cases, the radioactivity was accumulated in the gallbladder. These results suggest that the 99mTc chemical state, low-hydrolyzed state, relates to the bile excretion behavior of this complex, a potentially useful cholescintigraphic agent.     

Evaluation of a new hypercrosslinked polymer as a sorbent for solid-phase extraction of polar compounds

A new hypercrosslinked polymer (HXLGp) with hydrophilic character due to the presence of hydroxyl moieties has been tested as a sorbent for the solid-phase extraction (SPE) of several polar compounds from water samples. This new sorbent enables the on-line extraction of 300 ml of sample with recoveries higher than 80% for polar compounds such as oxamyl, methomyl or desisopropylatrazine (DIA). The HXLGp has also been compared to other commercially available sorbents such as Oasis HLB (hydrophilic macroporous), to hydrophobic hypercrosslinked resins and to a previously synthesized sorbent based on N-vinylimidazole-divinylbenzene. The results are consistently better with the new synthesized sorbent. The method was successfully applied to the on-line SPE-HPLC of tap and river water samples. The validation with river water samples provided good linearity range and detection limits between 0.03 for methomyl and 4-nitrophenol (4NP) to 0.2 microg l(-1) for phenol (Ph).     

Amperometric detection of antibodies in serum: performance of self-assembled cyclodextrin/cellulose polymer interfaces as antigen carriers

A bifunctionalised carboxymethyl-cellulose polymer bearing adamantane units and an antigenic fragment forms a highly stable interfacial complex with a βCD-containing surface. This allows the highly sensitive detection of antibodies using an amperometric immunosensor.     

Synthesis of methyl methacrylate star-branched polymer with divinylbenzene as a linking agent via controlled/living photopolymerization

HTEMPO-functionalized central cores were formed with divinylbenzene in ’’core first’’ method,and the four or five arms star polymers were built via controlled/living free radical photopolymerization.The four arms star polymers were also prepared with controlled/living free radical photopolymerization in ’’arm first’’ method.The resulting polymers had been confirmed by GPC and 1 H NMR.It showed that the star polymers had low polydispersities and molecular weight(M n) with the 85,000-560,000 g/mol range.     

Chlorosulfonylisocyanate as a chlorinating agent

CSI rather than adding to the double bond in 1, chlorinates the aromatic ring.