Syntheses and characterizations of copolymers of dicyanoquinone methides with α-acetoxystyrenes

Summary 7,7-Dicyanoquinone methides (1a-b) copolymerized spontaneously with substituted -acetoxystyrenes (2a-b) in benzene at 60 °C to give alternating copolymers (poly(1a-b-co-2a-b)) with the molecular weights of 8–60×10⁴ in 42–66% yields. When these copolymers were heated under nitrogen, they eliminated acetic acid quantitatively at around 200 °C to be converted to the copolymers (poly(3a-d)) with olefinic bonds, which were characterized by infrared and nuclear magnetic resonance spectroscopy. Alternating copolymers and the corresponding copolymers with olefinic bonds were amorphous, and capable of being cast from their chloroform solutions into transparent, tough films.     

Microstructure of copolymers of vinylidene cyanide,methacrylonitrile and acrylonitrile with methyl α acetoxyacrylate,a captodative monomer

Summary Copolymers of vinylidene cyanide (1a) methacrylonitrile (1b) and acrylonitrile (1c) with a captodative monomer, methyl acetoxyacrylate were synthesized by radical copolymerization and their microstructures were studied by ¹³C NMR spectroscopy.The copolymer of 1a with methyl -acetoxyacrylate (2) has mostly an alternating structure but the copolymers of 1b and 1c with 2 are rather statistical. The measurement of their reactivity ratios for these two reactions is in agreement with the proposed structures.     

Ionic liquids as co-solvents for zwitterionic copolymers and the preparation of poly(vinylidene fluoride) blend membranes with dominated β-phase crystals

A new series of green solvents that constituted with ionic liquids (ILs) and dimethyl acetamide (DMAc) were developed as good solvents for zwitterionic copolymers, and the dissolutions of amphiphilic copolymers carrying carboxylbetaine and sulfonatebetaine in these new solvents were studied. It was determined that the commonly found ILs such as 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF₄), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) and many others were all effective co-solvents for zwitterionic copolymer with carboxylbetaine groups. However, the 1-methylimidazolium trifluoromethanesulfonic ([MIM]CF₃SO₃) instead of the [BMIM]BF₄ was proved as an effective co-solvent for the copolymer carrying sulfonatebetaine units. These newly designed mix-solvents were also good solvents for poly(vinylidene fluoride) (PVDF) and their influences on the crystallization as well as the formation of PVDF membranes were investigated. Our results had demonstrated that blend membranes with zwitterionic additives could be facilely prepared with many new solvent candidates.     

Selenium dioxide reaction of substituted diphenacyl sulfides: generation of α -ketoacids

The attempted selenium dioxide oxidation of substituted diphenacyl sulfides in anticipation of further functionalization led to a series of α -ketoacids 3 via oxidation followed by C?S bond cleavage. Two minor products, 5 and 6, have also been isolated and a mechanistic pathway for the formation of 3, 5 and 6 has been proposed.     

Reactions of α -sulfone disulfides with sulfinate anions

Degenerate substitution reactions (at carbon) between the appropriate sulfinic acid salts and tosylmethyl methyl or mesylmethyl methyl disulfides have formed symmetrical disulfone disulfides in moderate yields. These products form in a redox process involving sulfinate anions following partial skeletal disassembly arising from rupture of the SS bond. The reaction of mesylmethyl methyl disulfide and sodium methanesulfinate provides a natural product, dysoxysulfone, in low yield.     

Investigation of the Structure and Piezoelectricity of Poly(vinylidene fluoride–trifluroethylene) Copolymer Doped with Different Dyes

The structure and piezoelectricity of poly(vinylidene fluoride–trifluroethylene) copolymer doped with crystal violet (CV), Coumarin 2 (C2), and N,N-Dimethyl-4-nitro-4-stilbenamine (DANS) were investigated by several techniques. H- and J-aggregates are formed in the CV and C2 doped copolymer, respectively, while DANS doped copolymer showed lamella structure. Moreover, the application of pressure-induced crystalline phase in the CV doped copolymer and TSDC measurements revealed that the ferroelectric to paraelectric transition peak has taken place in the C2 and DANS doped copolymer. Kohlrausch-Williams-Watts stretched function was applied to estimate the relaxation time of the piezoelectric current. The pyroelectricity is found to be dipole-moment-dependent.     

Syntheses,structures and properties of a series of 3s–5d–4f mixed metal substituted sandwich-type arsenotungstates

A class of 3s–5d–4f mixed metal substituted sandwich-type arsenotungstates [H₂N(CH₃)₂]₈H₃[LnNa(H₂O)₄(OH)WO(H₂O) (B-α-AsW₉ O₃₃)₂]·8H₂O [Ln = La^III (1), Ce^III (2), Pr^III (3)] have been isolated from an aqueous solution reaction system (pH = 4) of Na₂WO₄·2H₂O, C₂H₇N·HCl, NaAsO₂ and Ln(NO₃)₃·6H₂O and structurally characterized by elemental analyses, IR spectra, UV spectra and single-crystal X-ray diffraction. It is the most prominent in 1–3 that the [LnNa(H₂O)₄(OH) WO(H₂O)(B-α-AsW₉O₃₃)₂]^11 − polyanion consists of two trivacant Keggin [B-α-AsW₉O₃₃]^9 − moieties linked by one [WO(H₂O)]^4 + group and a dimeric [LnNa(H₂O)₄(OH)]^3 + group resulting in the special 3s–5d–4f mixed metal substituted sandwich-type assembly. Interestingly, lanthanide and sodium ions simultaneously occupy the two positions located at the central belt of 1–3 with the site occupancy of 50% for each position. Moreover, the electrochemical and electrocatalytic properties of only 1 and 2 have been measured by cyclic voltammetry (CV) in 0.5 mol·L^− 1 Na₂SO₄ + H₂SO₄ aqueous solution. 1 and 2 illustrate electrocatalytic activities for the hydrogen peroxide reduction.     

The copolymerization of substituted styrenes with α-methylene-γ-butyrolactone

Summary Copolymers of halogenated styrenes and -methylene--butyrolactone were synthesized in bulk via free radical initiation. The polymerizations, in most cases, proceeded rapidly to high conversion. The high conversions obtained necessitated the use of high conversion methods to calculate reactivity ratios. In all the copolymerizations the -methylene--butyrolactone proved to be the more reactive monomer.     

Polynorbornene copolymers with pendent o-carborane and carbazole groups: Novel side-chain donor–acceptor copolymers for turn-on sensing of nucleophilic anions

Vinyl-type polynorbornene copolymers with side-chain o-carborane (1-phenyl-o-carborane for P1–P3; 1-methyl-o-carborane for P4) and carbazole moieties were produced by vinyl addition copolymerization of norbornene monomers using a Pd(II) catalyst in combination with 1-octene chain transfer agent. The catalytic system provided well-defined copolymers with controlled incorporation of monomers. The copolymers possessed high thermal stability with high decomposition (T_d5 > 410 °C) and glass transition temperatures (T_g > 350 °C). Treatment of the closo-copolymers (P1–P4) with excess KOH in refluxing EtOH/THF led to degradation of the closo-carborane cage to produce nido-copolymers (nido-(P1–P4)). While P1–P3 exhibited a weak carbazole-based fluorescence, the corresponding nido-copolymers gave rise to a 2.0–3.6-fold increase in PL intensity depending on the comonomer content. An electrochemical study and comparative PL results of P4 and nido-P4 suggest that photoinduced charge transfer from carbazole donors to 1-phenyl-o-carborane acceptors was responsible for the weak fluorescence of P1–P3.     

Syntheses of diblock copolymers: poly(2-methylpropene)-b-poly(α-amino acid)

Summary Diblock copolymer poly (2-methylpropene)-b-poly (-amino acid) was obtained by polymerization of the corresponding N-caboxy anhydride initiated by a poly (2-methylpropene) bearing a terminal amine in dioxane/CH₂Cl₂ mixture. Copolymers were analyzed by FT IR, ¹H and ¹³C NMR. of the -amino acid segment determined by ¹H NMR fits well with those obtained by a theoretical calculation.     

Physico-chemical,mechanical and cytotoxicity characterizations of Laponite®/alginate nanocomposite

Combining clay minerals containing silica with polymers can improve the performance of polymers in biomedical applications by the synergistic combination of physico-chemical and biological properties of both phases. In this study, Laponite® — a synthetic biocompatible and biodegradable silicate clay mineral, was combined with alginate to improve alginate mechanical and biological characteristics. The physico-chemical properties (porosity, degradation, swelling, crystalline structure, compressive strength, and injectability) and biological responses (cytotoxicity and cell morphology) of the Laponite/alginate nanocomposites were investigated in the study. The results showed that the incorporation of Laponite into alginate significantly enhanced alginate compression strength without hindering its injectability when the percentage of clay mineral was below 50%. The prepared clay polymer nanocomposites (CPN) were not toxic and the viability of cells cultured in its extract was indeed higher than alginate alone. However, these prepared CPN poorly supported cell adhesion, probably due to the high degradation rate of the materials.     

Construction of inter-chain polymers and the investigation into Friedel–Crafts alkylation of styrene–acrylonitrile copolymers with chloroprene rubber and characterization

In this study, the Friedel–Crafts alkylation was realized in a solvent free processing of styrene–acrylonitrile copolymers/chloroprene rubber (SAN/CR) molten blending which contributes the formation of SAN-co-CR co-polymers and improved compatibility between SAN and CR. The properties of several Lewis acid compounds were tested as catalysts among which AlCl₃ was the most efficient. The effects of blending temperature and time on the co-polymer formation in situ were also investigated. The methodology of weighing and Fourier transform infrared analyses indicated that the reaction degree increases with increasing blending temperature and time in the ranges of this study. The micro-structures and reaction mechanisms of the resulted SAN-co-CR polymers and morphological structures of SAN/CR/AlCl₃ blends were characterized as well by differential scanning calorimetry, FT-IR spectra, GPC and scanning electron microscopy. The results showed that the inter-facial reactions between SAN and CR have been effectively improved. Moreover, the inter-chain structure of SAN-co-CR co-polymers was proposed which is different from general grafting or blocking co-polymers.     

Esterification of fatty acids with glycerol over Fe–Zn double-metal cyanide catalyst

Solid Fe–Zn double-metal cyanide (DMC) complex exhibits high catalytic activity for esterification of fatty acids (FA) with glycerol. DMC catalysts with varying acidities were prepared by synthesizing the material at four different temperatures (10, 25, 50 and 80 °C). The catalyst prepared at 50 °C exhibited highest catalytic activity. Catalytic activity of DMC was influenced by both acidity and surface area. Complete conversion of FA was achieved at 140–200 °C under atmospheric pressure. Chain length of FA was found to influence the rate of reaction and product selectivity.     

Blends of ethylene–octene copolymers with different chain architectures – Morphology,thermal and mechanical behavior

Blends of two elastomeric ethylene–octene copolymers with similar octene contents having a random (ORC) and a blocky architecture (OBC) are prepared by melt mixing. The thermal and mechanical properties of ORC, OBC and their blends are investigated by DSC, dynamic mechanical analysis and tensile tests. The morphology of the semi-crystalline samples is studied by AFM and WAXS. Two types of crystals have been observed: (i) Orthorhombic crystals forming lamellae with an estimated thickness of about 13 nm composed mainly of long polyethylene-like sequences of OBC that melt a temperature of about 120 °C and (ii) fringed micellar crystals with a thickness of 2–4 nm formed basically by short polyethylene-like sequences of ORC that have melting temperatures between 30 and 80 °C. The amorphous phase contains a relatively homogeneous mixture of segments of both components indicated by the relatively uniform shape of the loss modulus peaks from dymamic-mechanical measurements for all investigated copolymers and blends. ORC crystallization is hindered in blends as indicated by lower melting enthalpies. This might be related to the high octene content of the amorphous phase at the relevant crystallization temperature as well as geometrical constraints since ORC crystallization occurs in an already semi-crystalline polymer. The results of tensile tests show that the mechanical behavior can be tailored via blend composition and morphology of the semi-crystalline material. The findings clearly indicate that blending is a powerful strategy to optimize the properties of polyolefin-based copolymers.     

Syntheses and characterizations of two novel Ln(III)–Cu(II) coordination polymers constructed by Pyridine-2,4-dicarboxylate ligand

Two novel three dimension Ln(III)–Cu(II) coordination polymers [Gd₂Cu(pydc)₄(H₂O)₆]_n and [Sm₂Cu₃(pydc)₆(H₂O)₆]_n were prepared by the hydrothermal reactions of CuO, Ln₂O₃ (Ln = Gd, Sm), H₂pydc (H₂pydc = 2,4-pyridinedicarboxylic acid) and characterized by single-crystal X-ray diffraction analysis.     

Preparation of pH-responsive membranes with amphiphilic copolymers by surface segregation method☆

Novel pH-responsive membranes were prepared by blending pH-responsive amphiphilic copolymers with pol-yethersulfone (PES) via a nonsolvent-induced phase separation (NIPS) technique. The amphiphilic copolymers bearing Pluronic F127 and poly(methacrylic acid) (PMAA) segments, abbreviated as PMAAn–F127–PMAAn, were synthesized by free radical polymerization. The physical and chemical properties of the blend membranes were evaluated by scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectrum, water con-tact angle, Zeta potential and X-ray photoelectron spectroscopy (XPS). The enrichment of hydrophilic PMAA seg-ments on the membrane surfaces was attributed to surface segregation during the membrane preparation process. The blend membranes had significant pH-responsive properties due to the conformational changes of surface-segregated PMAA segments under different pH values of feed solutions. Fluxes of the blend membranes were larger at low pH values of feed solutions than that at high pH values. The pH-responsive ability of the mem-branes was enhanced with the increase of the degree of PMAA near-surface coverage.     

Synthesis and characterization of a new polymer–drug conjugate with pH-induced activity

A well-defined, stimuli-responsive tetrapolymer with pH-responsive characteristics and targeting specificity has been synthesized by radical copolymerization of methacrylic acid, N-(2-hydroxypropyl)methacrylamide, methacryloyl glycylglycyl sulfamethoxazole, and N-(methacryloyl)glycylglycine 4-nitrophenyl ester. The structure and properties of tetrapolymer were investigated by NMR, FT-IR, UV–visible absorption, TEM and gel permeation chromatography. Incorporation of maleimide linker into tetrapolymer facilitates its conjugation with antibody fragments, as demonstrated by the solid-phase immunoassay experiments. The TEM image shows that tetrapolymer had self-assembled a spherical micelle with a diameter ranging from 50 to 150 nm. Altering the pH of the solution leads to a different extent of aggregation at pH 6.5–3.5, responding in accordance with the properties associated with the extracellular environment of solid tumors and endocytosis. Furthermore, fluorescence spectroscopy indicated a critical micelle concentration (CMC) of 1 mg/mL. Because of the solvation and ionization effects, the tetrapolymer showed considerably enhanced antibacterial activities against Escherichia coli in the presence of DMSO and the antibacterial activity increased with decreasing pH value.     

Electro-deposition and characterizations of nickel coatings on the carbon–polythene composite

Nickel coating on the carbon–polythene composite plate was prepared by electrodeposition in a nickel sulfate solution in this work. The morphology and cross-sectional microstructure of the nickel coating were examined by scanning electron microscope (SEM) and optical microscope (OM), respectively. The influence of bath temperature on the nickel deposition rate was investigated experimentally. The adhesion between the coating and the substrate was evaluated by the pull-off test. The corrosion behavior of the coating in an aqueous solution of NaCl was studied by electrochemical methods. The results showed that the nickel electrodeposition rate could reach up to 0.68 μm min⁻¹ on average under conditions of cathodic current density of 20 mA cm⁻² and bath temperature of 60 °C. It was confirmed that increasing the bath temperature up to 50 °C had a positive effect on the nickel deposit rate, while an adverse effect was observed beyond 60 °C. The adhesion strength between the nickel coating and the substrate can be more than 2.3 MPa. The corrosion potential of the bright coating in the NaCl solution was more positive than that of the dull coating, and the anodic dissolution rate of the bright coating was also far lower at the same polarization potential compared with the dull coating.     

Synthesis of block copolymers of ε-caprolactone and lactide in the presence of lithium t-butoxide

Summary High molecular mass copolymers with microphase separation can be obtained in block copolymerization of -caprolactone with L,L- and D,L-lactide carried out in the presence of lithium t-butoxide. A kind of solvent applied strongly affects the molecular mass and polydispersity index of obtained copolymers.The study has been supported by the research program (Project 4-1743) of the Committee of Scientific Research in Poland.     

A new type of copper coordination polymer based on γ-aminobutyric acid: Syntheses,structures and magnetic properties

A copper coordination polymer with γ-aminobutyric acid (GABA), {[Cu₃(GABA)₂(NO₃)₂(OH)₂(H₂O)₂] (NO₃)₂·2H₂O}_n (1), has been synthesized and characterized by single-crystal X-ray diffraction, IR, PXRD, TGA and elemental analysis. It exhibits a 1D chain structure including μ₃-OH-Cu₃ cluster as a building block. The strong H-bonding links these chains to form 2D sheet structure and the main intermolecular interaction between the 2D sheets is electrostatic interaction. According to the crystal structure of complex 1, the magnetic properties of complex 1 have been investigated by the cluster and cycle magnetic coupling models. There are three different magnetic coupling pathways of Cu(II) (J₁, J₂, J₃) from each method and the resulting fitted curves based on the magnetic parameters of both methods compare well with the experiment values.