Synthesis and Characterization of Some Poly(1,2-Phenylenedithiocarbamate)–Metal Complexes

Poly(1,2-phenylenedithiocarbamate) (PPDTC) was prepared by the reaction of 2-aminothiophenol with carbon disulfide followed by condensation through the removal of H₂S gas. PPDTC was used as a ligand to prepare four poly(1,2-phenylenedithiocarbamate)–metal complexes of iron(II), cobalt(II), copper(II), and lead(II), by refluxing with the metal salts. The polymer and its metal complexes were investigated by elemental analyses, UV–visible and IR spectroscopy, inherent viscosity, and magnetic susceptibility. The DC electrical conductivity variation with the temperature in the range 298–498 K of PPDTC and its polymeric copper complex was measured. Both polymer and polymer metal complexes showed an increase in electrical conductivity with an increase in temperature: typical semiconductor behavior. The proposed structure of the complexes is (MLX₂·mH₂O) _n .     

Synthesis,Characterization of Fulvic Acid–Poly(Methylmethacrylate) Graft Copolymers Based on Surface-Initiated Atom Transfer Radical Polymerization and its Effect on Performance of Poly(Lactic Acid)

Fulvic acid–poly(methylmethacrylate) graft copolymers were synthesized by surface-initiated atom transfer radical polymerization with fulvic acid. The result demonstrated that the hydrophobicity of fulvic acid–poly(methylmethacrylate) was improved after modification by surface-initiated atom transfer radical polymerization. Furthermore, poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites were prepared to improve the performances of poly(lactic acid) by blend melting. Compared to poly(lactic acid) with X_c of 5.38%, the X_c of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was 19.94%. Moreover, the impact strength of poly(lactic acid)/fulvic acid–poly(methylmethacrylate) composites was increased by 5.19% compared to poly(lactic acid). In all, this study provided an effective and feasible method for optimizing interface performance and enhancing the thermal stability of poly(lactic acid).     

Synthesis and Characterization of Silica–Polymer Nanocomposites Functionalized with Piperazine for the Synthesis of β-Nitro Alcohols

Abstract  

In order to compare the activity and selectivity for the synthesis of β-nitro alcohols, piperazine was functionalized directly and after surface modification into the ordered mesoporous SBA-15 framework. The materials were characterized by powder X-ray diffraction, N₂-adsorption–desorption isotherm, FT-IR, SS-NMR and scanning electron microscopy. The catalyst synthesized via surface modification under solvent free conditions showed very high activity and selectivity of β-nitro alcohols compared to the one synthesized by direct functionalization of SBA-15. Finally the possible reaction pathways were explained mechanistically.     

Vapor Permeation and Pervaporation of Aqueous 2‐Propanol Solutions through the Torlon® Poly(amide imide) Membrane

Abstract

In the present study, vapor permeation and pervaporation of aqueous 2‐propanol mixtures were investigated using Torlon^® poly(amide imide) as a membrane material. Torlon membranes preferentially permeated H₂O from aqueous 2‐PrOH mixtures both by vapor permeation and pervaporation. Diffusion experiments led to the conclusion that both solubility selectivity and diffusivity selectivity showed a preference for H₂O. Solubility selectivity is by far the dominant factor governing permselectivity, and as a result, Torlon membranes showed permselectivity toward water in vapor permeation and pervaporation. The present study showed that Torlon^® poly(amide imide) is a membrane material potentially applicable to the dehydration of water miscible organics.     

Separation of Acetic Acid‐Water Mixtures through Poly(Vinyl Alcohol)/Poly(Acrylic Acid) Alloy Membranes by Using Evapomeation and Temperature Difference Evapomeation Methods

Abstract

Separation of acetic acid‐water mixtures by using evapomeation (EV) method were carried out over the full range of compositions at temperatures varying from 30 to 55°C using poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) (75/25) (v/v) alloy membranes. PVA/PAA membranes gave separation factors of 110–5711 and permeation rates of 2.3×10^?4–1.53×10^?1 kg/m²h, depending on the operation temperature and feed mixture composition. The temperature dependence of the permeation in EV was expressed by the Arrhenius type expression and the activation energy was calculated as 9.15 kcal/mol. More efficient EV technique, which is called temperature difference evapomeation method (TDEV) was also applied to PVA/PAA membranes to separate acetic acid‐water mixtures; high permeation rates (1.7×10^?3–3.0×10^?1 kg/m²h) and separation factors (1335–8924) were obtained for each of the studied feed compositions. Azeotropic mixture of acetic acid and water was also separated by TDEV method with a separation factor of 297 and permeation rate of 1.50×10^?1 kg/m²h.     

Synthesis and Characterization of β-Cyclodextrin Functionalized Ionic Liquid Polymer as a Macroporous Material for the Removal of Phenols and As(V)

β-Cyclodextrin-ionic liquid polymer (CD-ILP) was first synthesized by functionalized β-cyclodextrin (CD) with 1-benzylimidazole (BIM) to form monofunctionalized CD (βCD-BIMOTs) and was further polymerized using a toluene diisocyanate (TDI) linker to form insoluble CD-ILP (βCD-BIMOTs-TDI). The βCD-BIMOTs-TDI polymer was characterized using various tools and the results obtained were compared with those derived from the native β-cyclodextrin polymer (βCD-TDI). The SEM result shows that the presence of ionic liquid (IL) increases the pore size, while the thermo gravimetric analysis (TGA) result shows that the presence of IL increases the stability of the polymer. Meanwhile, Brunauer-Emmett-Teller (BET) results show that βCD-BIMOTs-TDI polymer has 1.254 m²/g surface areas and the Barret-Joyner-Halenda (BJH) pore size distribution result reveals that the polymer exhibits macropores with a pore size of 77.66 nm. Preliminary sorption experiments were carried out and the βCD-BIMOTs-TDI polymer shows enhanced sorption capacity and high removal towards phenols and As(V).     

Synthesis and Structural Characterization of Triorganotin(IV) Derivatives with 2,2′-Thiodiglycolic Acid and 3,3′-Thiodipropionic Acid

The synthesis and structural characterization of four novel triorganotin(IV) complexes, {(R₃Sn)₂[C₂H₄S(COO)₂]} _n (R = Me: 1), {(R₃Sn)₄[C₂H₄S(COO)₂]₂} _n (R = nBu: 2), {(R₃Sn)₂[C₄H₈S(COO)₂]} _n (R = Me: 3; nBu: 4) were obtained by the reaction of 2,2′-thiodiglycolic acid, 3,3′-thiodipropionic acid and the corresponding R₃SnCl (R = Me, nBu) with potassium hydroxide in methanol. All the complexes were characterized by elemental analysis, Fourier transform infrared and nuclear magnetic resonance (¹H, ¹³C, ¹¹⁹Sn) spectroscopies, X-ray crystallography and thermogravimetric analyses. The crystal structures show that 1 has 2D network structure in which 2,2′-thiodiglycolic acid acts as a tetradentate ligand coordinating to the trimethyltin(IV) ions. Complexes 2, 3, and 4 are 3D metal-organic framework structures in which the deprotoned acids act as a tetradentate ligand afforded by four oxygen atoms.     

Synthesis and Characterization of Perovskite-Type Oxides La1−xMxCoO3 (M = Ce,Sr) for the Selective CO Oxidation (SELOX)

Perovskite-type oxides La_1?xM_xCoO₃ (M = Ce, Sr) were prepared by citrate method, characterized and evaluated in the selective CO oxidation (SELOX-CO). The insertion of low Cerium or Strontium content generated solids with a single phase related LaCoO₃ perovskite. For higher contents we observed segregation of CeO₂ and SrCO₃. The iso-structural substitution favors the formation of vacancies. The SELOX-CO showed 100 % CO conversion at 200 °C. Higher temperatures favored hydrogen oxidation and methanation.     

Synthesis,Characterization, and Evaluation of Gel‐Type Poly(4‐Vinylpyridine) Resins for Plutonium Sorption

Abstract

Three different cross‐linked (4, 8, and 12%) gel‐type strong‐base poly(4‐vinylpyridine) resins (PVP) have been synthesized and characterized by elemental analysis, IR, exchange capacity, and moisture content. The uptake of plutonium and uranium was measured as a function of nitric acid concentration using all the three PVP resins. Plutonium sorption and elution kinetics experiments were also performed on all three PVP resins and compared with the benchmark, a gel‐type quarternary ammonium type anion‐exchange resin. The plutonium sorption rate decreases with the increase in cross‐linkage of the resin. All the three PVP resins exhibit better elution kinetics compared to the benchmark. The results on kinetic experiments performed on all three‐gel‐type resins indicated 8% gel‐type PVP resin with 50–100 mesh as a better candidate for plutonium processing or purification. Radiation degradation studies were carried out on the 8% PVP resin by gamma irradiation up to 200 MRad. The irradiated resins were characterized by IR, TGA, and SEM.

The exchange capacity, moisture content, and plutonium uptake were also evaluated for the irradiated PVP resins in comparison with the benchmark. The results indicated a better radiation stability for PVP resin over the benchmark.     

A Hybrid Membrane of Poly(vinyl alcohol) and Phosphotungstic Acid for Fuel Cells

Proton conducting membranes composed of phosphotungstic acid (PWA) and poly(vinyl alcohol) (PVA) were prepared. Conductivity and Fourier transform infrared spectrometer(FTIR) measurements show that most of the acid embedded are stable in the PVA matrix when the membrane is immerged in water or methanol solution at room temperature. Conductivity of the composite membranes scatters around 10-3S·cm-1 at room temperature. The methanol crossover through the membranes is about an order of magnitude lower than that through Nafion 117 membrane.     

Surface Treatment of ZrO2 Nanoparticles with Biosafe Citric Acid and Its Utilization for the Synthesis of L-leucine Based Poly(Amide–Imide) Nanocomposites

This study aimed at preparing three nanocomposites of optically active poly(amide–imide) and zirconium dioxide (ZrO₂) inorganic nanoparticles through the ultrasonic process. First, the surface of ZrO₂ nanocomposites was chemically modified with bio-active citric acid in the basic media. Then, the poly(amide–imide) was reinforced with modified nanocomposites and three poly(amide–imide)/ZrO₂-citric acid nanocomposites were synthesized by ultrasonic irradiation. The poly(amide–imide) was prepared by polycondensation of N-trimellitylimido-L-leucine with 4,4′-diaminodiphenylsulfone using of triphenyl phosphite and molten tetra-n-butylammonium bromide as green media. The obtained poly(amide–imide)/ZrO₂-citric acid nanocomposites were characterized by different techniques.     

Sorption of U(VI) onto Layered Double Hydroxides of Mg and Al with β-Cyclodextrin from Aqueous Solutions

Theoretical Foundations of Chemical Engineering - The possibility of removing U(VI) from aqueous solutions using layered double hydroxides of Mg and Al, which contain β-cyclodextrin...     

Aggregation and Adsorption at the Air–Solution Interface of the Cetyltrimethyl Ammonium Tosylate With Two Poly(oxyethylene)–Poly(oxypropylene)–Poly(oxyethylene) Block Copolymers Aqueous Mixtures

The aqueous mixed systems (EO₇₆PO₃₀EO₇₆) (TBCP8400)—cetyltrimethyl ammonium tosylate (CTAT), and (EO₉₇PO₆₉EO₉₇) (TBCP12600)—CTAT were studied to determine both the bulk aggregation and the adsorbed monolayer at the air/water interface. Results were interpreted with the pseudophase separation model plus the regular solution theory for aggregates and monolayers. The behavior is different for TBCP8400–CTAT and TBCP12600–CTAT mixtures, but it is strongly non-ideal in both cases. In bulk, TBCP8400–CTAT mixtures produce aggregates more close to CTAT micelles having TBCP8400 as a solubilizate than the inverse. At low CTAT content, the interaction is repulsive becoming attractive at high TBCP8400 content. The TBCP12600–CTAT aggregates strongly differ from the structure of both pure component micelles, and the interaction is always repulsive. In both cases, the interaction seems not to be cooperative but gradual. CTAT effect on copolymers aggregates seems to be more similar to that of a zwitterionic surfactant than to that of an ionic one. However, CTAT is not included in the aggregates as an ion pair, as revealed by the ionization degree results. It seems that cetyltrimethyl ammonium and tosylate ions have different effects on aggregates which in part are opposite. The adsorbed monolayers also show different behavior. In TBCP8400–CTAT system, the monolayer is mainly a CTAT one with inclusion of TBCP8400 as a monolayer-soluble impurity. However, the inclusion of the non-ionic surfactant alters the structure of the monolayer, which differs from that of the pure CTAT one. The area per adsorbed molecule (A₀) is systematically higher than the ideal and computed ones. The system TBCP12600–CTAT shows a monolayer composition which is almost the same that the overall surfactant mixture composition, and the monolayer structure differs from both the pure-TBCP12600 and the pure-CTAT monolayers ones. The experimental A₀ values are systematically lower than the ideal and the computed ones. Then, in both cases the A₀ values for the pure components do not remain invariable in the mixed monolayer. The phenomenon is interpreted on the basis of the conformation of the copolymers adsorbed at the air/solution interface.     

Synthesis and Characterizations of Poly(aniline)–Natural Clay Nanocomposites

Aniline (ANI) was polymerized under inert atmosphere in the presence and absence of natural clay initiated by peroxydisulphate (PDS) in an aqueous acidic medium. While increasing the amount of clay the rate of polymerization (R_p) was decreased and showed first order dependence with respect to amount of clay. The % yield was also decreased while increasing the amount of clay due to the confinement of monomer radical cation by the clay. The FTIR spectrum confirmed the presence of benzenoid and quinoid units in the polyaniline (PANI) structure. DSC inferred the absence of T_m due to cross-linking reaction of PANI because of de-doping process. AFM showed the distorted spherical morphology of uniformly dispersed clay platelets in the PANI. The % weight residue remain above 700°C is increased with the increase of amount of clay, which was confirmed by TGA method. Due to confinement effect the intrinsic viscosity value of PANI—nanocomposites were decreased with the increase of amount of clay in the system. PANI-nanocomposites showed improved d.c. conductivity value than the pristine PANI. Suitable mechanism was proposed to explain the experimental results obtained.     

Investigation of the State of Bis(2,4,4‐Trimethylpentyl)dithiophosphinic Acid in Nonane and Toluene Solutions

An IR spectroscopy method is used to examine the state of nonane and toluene diluted bis(2,4,4‐trimethylpentyl)dithiophosphinic acid (HR) in the concentration range of 0.025–1.0 M. It was found that in contrast to the “inert” solvent nonane, in which marked self‐association of the dithiophosphinic acid due to the formation of intermolecular SH…S hydrogen bonds begins at an HR concentration of ～0.1 M, in the aromatic diluent toluene this process begins at HR_total ?0.4 M. This result is explained by the interaction of the proton of the S‐H group of the dithiophosphinic acid with the π‐electron system of the toluene aromatic ring and the formation of SH…π hydrogen bonds, preventing the self‐association of the organic acid. The presence of the monomeric, dimeric, and tetrameric forms of the extractant in solution was shown to best describe the bis(2,4,4‐trimethylpentyl)dithiophosphinic acid‐nonane system. The formation constants of the dimers (K₂ = 0.78 ± 0.07) and tetramers (K₄ = 3.42 ± 0.26) have been calculated.     

Preparation and Performance of Poly(Lactic Acid)-γ-Cyclodextrin Inclusion Complex-Poly(Lactic Acid) Multibranched Polymers by the Reactive Extrusion Process

The poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) multibranched polymers were prepared by reactive extrusion process with L-lactide as raw material, stannous octoate as catalyst and the carboxyl poly(lactic acid)-γ-cyclodextrin inclusion compound as cores prepared by ultrasonic coprecipitation and carboxylation reaction. It was shown that the comprehensive performance of poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) had been significantly improved compared with liner poly(lactic acid) by the study of structure and properties. Thus, the novel poly(lactic acid)-γ-cyclodextrin inclusion complex-poly(lactic acid) multibranched polymers have a potential use in biomedical materials. This study provided a simple and feasible preparation method for improving the performance of poly(lactic acid).     

Preparation and Properties of α-Cellulose Short Fiber-Reinforced Poly(lactic Acid) Composites

The objective of this study is to fabricate the PLA/α-cellulose composites and to investigate the effect of α-cellulose short fibers on the toughness improvement of PLA. To homogeneously disperse the polar α-cellulose in the non-polar PLA matrix, the as-received α-cellulose was subjected to surface modification using stearic acid to impart the hydrophobic characteristics to the short fibers. The α-cellulose fibers dispersed more homogeneously in PLA through this modification, and consequently, the fiber pull-out and longer micro-crack length could improve the toughness and damping property of the resulting PLA composites. The inclusion of α-cellulose short fibers considerably decreased the spherulite dimension of the PLA/α-cellulose composites to accommodate larger deformation through grain boundary sliding. The PLA/α-cellulose composite improved its toughness by three times that of the neat PLA with low α-cellulose content (～4 wt.%), and maintained its transparency.     

Lipase Catalyzed Synthesis and Thermal Properties of Poly(dimethylsiloxane)–Poly(ethylene glycol) Amphiphilic Block Copolymers

Resin immobilized lipase B from Candida antarctica (CALB) was used to catalyze the condensation polymerization of two difuctional siloxane and poly(ethylene glycol) systems. In the first system, 1,3-bis(3-carboxypropyl)tetramethyldisiloxane was reacted with poly(ethylene glycol) (PEG having a number-average molecular weight, M_n = 400, 1000 and 3400 g mol⁻¹, respectively). In the second system, α,ω-(dihydroxy alkyl) terminated poly(dimethylsiloxane) (HAT-PDMS, M_n = 2500 g mol⁻¹) was reacted with α,ω-(diacid) terminated poly(ethylene glycol) (PEG, M_n = 600 g mol⁻¹). All the reactions were carried out in the bulk (without use of solvent) at 80 °C and under reduced pressure (500 mmHg vacuum gauge). The progress of the polyesterification reactions was monitored by analyzing the samples collected at various time intervals using FTIR and GPC. The thermal properties of the copolymers were characterized by DSC and TGA. In particular, the effect of the chain length of the PEG block on the molar mass build up and on the thermal stability of the copolymers was also studied. The thermal stability of the enzymatically synthesized copolymers was found to increase with increased dimethylsiloxane content in the copolymers.