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.     

Synthesis,structure and luminescent property of a new europium-based coordination polymer constructed from biphenyl-3,4′,5-tricarboxylic acid

A new 3D lanthanide metal–organic framework Eu(BPT)(DMF)(H₂O)•(H₂O)_0.5] (1) has been synthesized by self-assembly of Eu(III) ions and ligand biphenyl-3, 4′, 5-tricarboxylate under solvothermal reaction conditions. X-ray crystallography reveals that 1 exhibits a (3, 6)-connected topology, with dinuclear europium clusters as 6-connected nodes and C₂-symmetric ligands BPT as 3-connected nodes. In addition, the luminescence sensitization of 1 via excitation of the ligand is highly efficient.     

Synthesis and characterization of an isocyanurate–oxazolidone polymer: Effect of stoichiometry

Isocyanurate–oxazolidone polymers were synthesized by using various reactant stoichiometry of a diglycidyl ether of bisphenol-A (DGEBA) and a polymeric diphenyl methane diisocyanate (pMDI). The reaction was catalyzed by tris-2,4,6-dimethylaminoethylphenol (Ancamine K54). The effects of stoichiometry that the reaction had on the molecular structure and mechanical and thermomechanical properties were evaluated. Two main structures obtained from the reaction of DGEBA with pMDI, namely isocyanurate and oxazolidone, were clearly shown by Fourier transformed infrared spectroscopy (FTIR) analyses. It was found that the amount of DGEBA present determines the amount of oxazolidone formed. Where excess DGEBA was used, structural transformation reaction from isocyanurate to oxazolidone was observed. The amount of pMDI, on the other hand, influenced the amount of isocyanurate structure formed. As the relative amounts of isocyanurate and oxazolidone contents changed with stoichiometry of the reactants, the effects on the crosslink density in the samples were clearly shown by both mechanical and thermomechanical measurements. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 879–888, 2001     

Synthesis and characterization of copper gallium diselenide powders prepared from the sol–gel derived precursors

Copper gallium diselenide (CuGaSe₂) powders were synthesized via the sol–gel method followed by a selenization process. The sol–gel process can effectively reduce the required synthesis temperature to 400 °C due to enhanced reactivity and improved composition homogeneity. The amount of Cu₂Se impurity phase was decreased when sufficient Ga³⁺ was added to the precursors. CuGaSe₂ powders were successfully prepared when the Ga³⁺/Cu²⁺ molar ratio was increased to 2. The formation of CuGaSe₂ with a pure chalcopyrite structure was confirmed via the Rietveld refinement analysis. With decreasing Ga³⁺/Cu²⁺ molar ratios, the particle size of the prepared CuGaSe₂ powders was significantly enlarged because the copper selenide phase acted as a flux for the particle growth. The optical absorption spectra revealed the obtained CuGaSe₂ to have a band gap of 1.68 eV. The sol–gel method combined with the selenization process was demonstrated to provide a potential approach for fabricating CuGaSe₂ materials.     

Synthesis and characterization of aromatic polyamides derived from various derivatives of 4,4’-oxydianiline

Three aromatic diamines, 2,2′-diiodo-4,4′-oxydianiline (DI-ODA 2), 2,2′-bis[p-(trifluoromethyl)phenyl]-4,4′-oxydianiline (BTFP-ODA 3) and 2,8-diaminodibenzofuran (DADBF 5) were synthesized by using 4,4-oxydianiline (4,4′-ODA) as the starting material. New aromatic polyamides 6, 7 and 8 were prepared from these three diamines and six commercially available aromatic diacids by direct polycondensation, respectively. Polyamides 6 and 7 contained bulky iodide and p-trifluoromethylphenyl substitutents that would hinder the chain packing and increase the free volume. They exhibited good optical transparency in visible light region and showed excellent solubility in organic solvents such as DMSO, DMAc, DMF and NMP. Polyamides 8 containing planar dibenzofuran moieties had the highest glass transition temperatures and decomposition temperatures among these polyamides. Polyamides 6 had the lowest decomposition temperatures due to the presence of weak carbon–iodine bond. All of these polyamides showed amorphous nature evidenced by wide angle X-ray diffraction. No endothermic peaks were observed from DSC thermograms up to their decomposition temperatures. High optical transparency and excellent solubility combined with good thermal stability make these polyamides attractive for potential soft electronics applications.     

Photocurrent contribution from inter-segmental mixing in donor–acceptor-type polymer solar cells: A multiscale simulation study

Polymer solar cells possess a promising perspective for generating renewable energy at affordable costs, provided their performance and durability can be improved considerably. To this end, several experimental and theoretical techniques have been devised recently, establishing a direct link between local morphology, local opto-electronic properties and device performance. However, their reliability is still unclear to this day. Here, we demonstrate by using a recently developed particle-based multiscale solar cell approach and comparing its results with the ones of a field-based solar cell algorithm that inter-mixing of the electron-donor(D)- and -acceptor(A)-type of segments in a lamellar-like poly(9,9’-dioctylfluorene-co-bis-N,N'-(4-butylphenyl)-bis-N,N'-phenyl-1,4-phenylene-diamine)-poly(9,9'-dioctylfluorene-co-benzothiadiazole) (PFB-F8BT) blend causes that the major part of the charge generation and charge transport takes place inside the nanophases of the nanostructured polymer solar cells in agreement with recent experimental measurements and not, as commonly believed, at the visible domain boundaries of the DA interface. Moreover, we show that the contribution of the exciton dissociation efficiency to the internal quantum efficiency, due to inter-monomeric mixing, is significant and cannot be neglected in simulation studies at the nanoscale. Finally, we demonstrate that keto-defects on the fluorene moiety of the F8BT phase, induced by photo-oxidation, causes a simultaneous increase of the intra-chain contribution and decrease of the inter-chain contribution to the electronic current density, whereas in the reduced form the difference between both contributions is significantly smaller. This antagonistic effect leads to keto-induced electron trapping, resulting in a deteriorated electronic transport efficiency in devices with a photo-oxidized F8BT phase.     

Improved bulk-heterojunction polymer solar cell performance through optimization of the linker groupin donor–acceptor conjugated polymer

Two donor–acceptor conjugated polymers PCTBTC8 and PCTTBTC12 have been prepared from Suzuki coupling reactions between the 2,7-carbazole and alkoxy substituted 2,1,3-benzothiadiazole units with two different linker groups thiophene and thieno[3,2-b] thiophene, respectively. The polymer PCTTBTC12 with the thieno thiophene linker group possessed a red-shifted UV-vis absorption spectrum and similar HOMO level in comparison with PCTBTC8. BHJ polymer solar cells were fabricated to investigate the photovoltaic properties of the two polymers and the polymer PCTTBTC12 showed superior device performance than PCTBTC8 with a significantly improved current density. In addition, the hole only devices tests results indicated that the hole mobility of the polymer was increased by replacing the thiophene group with fused thieno thiophene as the linker. The relationships between the device performance with the light absorption, energy levels, BHJ film morphology and hole mobility are discussed in details. And the improved photovoltaic property of the polymer PCTTBTC12 probably can be contributed to the better light absorption spectrum and enhanced hole transporting ability related to the more electron rich nature and planar structure of the thieno[3,2-b] thiophene group.     

Synthesis and characterization of epoxy–silicone–polythiophene interpenetrating polymer network for corrosion protection of steel

Polymer alloys, particularly interpenetrating polymer networks (IPNs) exhibit excellent coating properties. Often combination of polymers result in IPNs with controlled morphologies and synergistic behavior. In this study, corrosion-resistant IPNs were prepared from immiscible resins (epoxy, silicone and thiophene) using a cross-linking agent and a catalyst. GPC, FTIR, NMR, TG, DTA and SEM studies used to fix the best performing IPN. Surface morphology studies using SEM confirm the incorporation of silicone and polythiophene in to the epoxy polymer to form homogeneously micro structured IPN. The heat-resistance of the IPN was determined as per ASTM 2485. The improved corrosion resistance of the IPN was evaluated by AC impedance measurements.     

Synthesis and evaluation of a ruthenium–copper oxide/silica catalyst derived from microemulsion processing

Bimetallic Ru–Cu catalysts supported on SiO₂ have been synthesized in microemulsions using sodium metasilicate (Na₂SiO₃), copper nitrate (Cu(NO₃)_2·3H₂O) and ruthenium chloride (RuCl₃) at 28 °C. The microemulsion system consists of sodium 1,4‐bis(2‐ethylhexyl) sulfosuccinate (AOT) and sodium dodecyl sulphate (SDS), cyclohexane, and an aqueous solution of sodium metasilicate or metal salts. The catalysts have been characterized by XPS, EDX/SEM with line scanning and they possess a very narrow pore size distribution (around 38 Å) and relatively high specific surface areas (around 400 m²/g). The catalytic results of the N₂O decomposition reveal that higher conversions of N₂O can be achieved by the catalysts synthesized from the microemulsion process at lower temperatures (around 400 °C).     

Synthesis and characterization of ABn-type α-cyclodextrin monomer and its hyperbranched polymer

To obtain well-defined structures of α-cyclodextrin (α-CD) based monomer and its hyperbranehed polymer (HBP), a modified α-CD molecule with one electron-rich alkene and many electron-poor acrylates was first prepared through the esterification reaction between mono-ester undecylenic acid-α-CD and acrylic acid. It was then utilized as an AB_n-type monomer for subsequent ADMET polymerization between alkene and acrylate using the second generation Hoveyda-Grubbs catalyst in homogeneous water/organic [D₂O/(CD₃)₂CO] mixtures via acyclic diene metathesis (ADMET) polymerization. A novel cyclodextrin-based HBP was obtained in prolonged reaction time. The monomer and HBP were characterized by NMR, elemental analysis, FTIR, and MALDI-TOF MS measurements. It was found that the actual molecular structures of both monomer and polymer were identical with the designed structures. The produced polymers have molecular weights within 13.2 and 56.3 kDa, and their polydispersity indices range from 2.78 to 2.63 by multiangle laser light scattering-gel permeation chromatography. The degree of branching was determined by ¹H NMR spectroscopy and the values ranges from 0.41 to 0.52.     

Synthesis and characterization of thiophene-based donor–acceptor type polyimide and polyazomethines for optical limiting applications

In this communication we describe the design and synthesis of four new conjugated polymers (P1–P4) based on 3,4-ditetradecyloxythiophene. The required diamine monomer was prepared by a unique catalyst-free reduction process using hydrazine hydrate. The structures of the intermediates and polymers were established by FTIR, ¹H NMR spectroscopy. Molecular weights of polymers were determined by gel permeation chromatographic (GPC) method. Their electrochemical properties were investigated by cyclic voltammetry and linear optical properties were determined by UV–Visible absorption and fluorescence emission spectroscopic techniques. Further, their nonlinear optical properties were evaluated by Z-scan technique using Nd:YAG laser. These polymers showed strong optical limiting behavior with two-photon absorption (2PA) coefficients of the order of 10^?10 m/W, which are comparable to that of good optical limiting materials reported in the literature. Also, it has been observed that the optical nonlinearity enhanced with the increase in donor–acceptor strength of the polymer backbone.     

Synthesis of organic–inorganic polymer hybrids from acrylate polymer having a triphenylimidazole moiety via π–π interactions

Polymer Bulletin - Organic–inorganic polymer hybrids were prepared utilizing π–π interactions. The sol–gel reaction of phenyltrimethoxysilane (PhTMOS) was carried out in...     

Production and characterization of hybrid BEH-PPV/PEO conjugated polymer nanofibers by forcespinning™

The fabrication of hybrid poly(2,5-bis(2′-ethyl-hexyl)-1,4-phenylenevinylene) (BEH-PPV) and polyethylene oxide (PEO) nanofibers is reported. Nanofibers were created using a novel production method that uses centrifugal rather than electrostatic force to produce nanofibers. The nanofiber production method exhibits high yield production of nanofibers enabling mass-production capabilities. Thermo-physical characterization and X-ray diffraction of bulk PEO and BEH-PPV was conducted, and the results are compared with the produced hybrid nanofibers. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Synthesis and characterization of conducting polymer composites based on polyaniline–polyethylene glycol–zinc sulfide system

Hybrid semiconducting polymer composites containing polyaniline, polyethylene glycol and zinc sulfide have been prepared in various combinations by in-situ polymerization of aniline using ammonium per disulfate in acidic medium. A biomimetic approach of controlled precipitation has been used. A mechanism of formation of these hybrid materials has been suggested in which polyethylene glycol works as a medium for diffusion-limited growth of various components during their precipitation. These materials have been characterized by a variety of spectroscopic techniques, differential scanning calorimetry, X-ray diffraction, scanning electron microscopy and alternating current impedance spectroscopy. Equivalent circuits for different contributions from grain, grain boundary and electrode for different systems have been determined with the help of complex non-linear least square analysis software. The microstructure-property correlation have been discussed along with the possible conduction mechanisms from the temperature dependence of conductivity as variable-dimension variable-range hopping for different compositions of single, double and triple composite materials.     

Synthesis and characterization of new Mg–O–F system and its application as catalytic support

The Mg–O–F system (MgF₂–MgO) with different contents of MgF₂ (100–0%) and MgO is tested as support of iridium catalysts in the hydrogenation of toluene as a function of the MgF₂/MgO ratio. Mg–O–F samples have been prepared by the reaction of magnesium carbonate with hydrofluoric acid. The MgF₂–MgO supports, after calcination at 500 °C, are classified as mesoporous of surface area (34–135 m²·g^− 1) depending on the amount of MgO introduced. The Ir/Mg–O–F catalysts have been tested in the hydrogenation of toluene. The highest activity, expressed as TOF, min^− 1, was obtained for the catalyst supported on Mg–O–F containing 75 mol%MgF₂.     

Synthesis and characterization of new poly(ether–ester–imide)s as a generation of soluble and thermally stable polymers

A new-type of dicarboxylic acid 6 was synthesized from the reaction of 1,4-bis[4-aminophenoxy]butane 4 with trimellitic anhydride 5 in a solution of glacial acetic acid/pyridine (Py) at refluxing temperature. 1,4-Bis[4-nitrophenoxy]butane 3 was prepared by reaction of 4-nitrophenol 1 with 1,4-dibromo butane 2 in N,N-dimethylformamide (DMF) solution. Then dinitro 3 was reduced to 1,4-bis[4-aminophenoxy]butane 4 by using 10% Pd–C, ethanol, and hydrazine monohydrate. So six new thermally stable and organosoluble poly(ether–ester–imide)s (PEEIs) 8a–f with good inherent viscosities were synthesized by the direct polycondensation reaction of new 1,4-bis[4-(trimellitimido)phenoxy]butane 6 with several aromatic diols 7a–f through direct polycondensation using tosyl chloride (TsCl)/pyridine (Py)/DMF system as condensing agent. The resulted polymers were fully characterized by means of FTIR and ¹H NMR spectroscopy, elemental analyses, inherent viscosity, solubility tests, differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), and derivative of thermogravimetric (DTG).     

Synthesis and characterization of precursor derived TiN@Si–Al–C–N ceramic nanocomposites for oxygen reduction reaction

The development of efficient and durable catalysts is critical for the commercialization of fuel cells, as the catalysts’ durability and reactivity dictate their ultimate lifetime and activity. In this work, amorphous silicon-based ceramics (Si–C–N and Si–Al–C–N) and TiN@Si–Al–C–N nanocomposites were developed using a precursor derived ceramics approach. In TiN@Si–Al–C–N nanocomposites, TiN nanocrystals (with sizes in the range of 5–12 nm) were effectively anchored on an amorphous Si–Al–C–N support. The nanocomposites were found to be mesoporous in nature and exhibited a surface area as high as 132 m²/g. The average pore size of the nanocomposites was found to increase with an increase in the pyrolysis temperature, and a subsequent graphitization of free carbon was observed as revealed from the Raman spectra. The ceramics were investigated for electrocatalytic activity toward the oxygen reduction reaction using the rotating disk electrode method. The TiN@Si–Al–C–N nanocomposites showed an onset potential of 0.7 V versus reversible hydrogen electrode for oxygen reduction, which seems to indicate a 4-electron pathway at the pyrolysis temperature of 1000°C in contrast to a 2-electron pathway exhibited by the nanocomposites pyrolyzed at 750°C via the Koutecky–Levich plot.     

Tautomerism of a compartmental Schiff base ligand and characterization of a new heterometallic CuII–DyIII complex — Synthesis,structure and magnetic properties

A crystal structure of a compartmental ligand N,N′-bis(2,3-dihydroxybenzylidene)-1,3-diaminopropane (H₄L = C₁₇H₁₈N₂O₄) (1) containing N₂O₂-inner and O₄-outer coordination sites and a characterization of its novel diphenoxo-bridged discrete dinuclear complex [CuDy(H₂L)(MeOH)(NO₃)₃]·2MeOH (2) are reported. The Schiff base ligand 1 crystallizes in the orthorhombic P2₁2₁2₁ space group with a molecule in a bent conformation. The compound at 100 and 293 K displays the keto-enol tautomerism with the equilibrium in both temperatures shifted with a different degree towards the zwitterionic keto-amino form. The quantum chemical calculations showed preferences for enol-imino form in a gas phase and for keto-amine in solutions. The keto-amino tautomer is stabilized by intermolecular interactions. The complex 2 crystallizes in the triclinic P-1 space group as a dinuclear compound with Cu^IIDy^III core. The Dy(III) ion is nine-coordinated whereas the coordination number of Cu(II) is five. The temperature dependence of the magnetic susceptibility and the field-dependent magnetization indicated that the interaction between Cu(II) and Dy(III) metal centers in 2 is ferromagnetic.     

Synthesis and characterization of microporous silica–alumina membranes

The development of microporous ceramic thin layers is of prime interest for sensors or gas separation membranes working at high temperature. Microporous silica membranes can be easily prepared by the sol–gel process. However the microporosity of pure silica is rapidly modified by steam at high temperature. One way to improve hydrothermal stability is to use mixed-oxide membranes. In this work, microporous silica–alumina membranes were prepared by a simple and robust sol–gel method. Tetraethoxysilane was mixed with an acidic alumina hydrosol. Urea was added for preparing the alumina hydrosol, for controlling the mixed-oxide network polycondensation and also as porogen agent. FTIR and ²⁷Al NMR spectroscopic analyses showed that for Si/Al molar ratios up to 6/1, homogeneous mixed oxides were obtained with a random distribution of Al and Si atoms in the oxide lattice based on tetrahedral units. The derived supported layers were crack-free as demonstrated by scanning electron microscopy (SEM) observations. Their microporosity was investigated using ellipsoporosimetry (EP) with films supported on flat dense substrates. He, N₂ and CO₂ permeance measurements were performed for membranes deposited on porous tubular substrates. The measured values of He/N₂ and He/CO₂ ideal selectivities are in agreement with the microporous nature of the prepared layers.     

Clay–polymer nanocomposites as a novel drug carrier: Synthesis,characterization and controlled release study of Propranolol Hydrochloride

Short half life of Propranolol Hydrochloride (PPN), an antihypertensive drug is a prime requirement to develop a formulation which could extend the release of PPN in the human body and also eliminate daily multiple dosage of PPN. In this study, a system of PPN loaded Montmorillonite–Poly lactic-co-glycolic acid (Mt–PLGA) nanocomposites has been developed. PPN incorporated PLGA nanoparticles have been compared with Mt–PPN–PLGA nanocomposites. Mt was used as sustained release carrier for PPN with addition of biodegradable polymer PLGA by preparing Mt–PPN–PLGA nanocomposites by double emulsion solvent evaporation method.The drug encapsulation efficiency and drug loading capacity of synthesized products were estimated with HPLC including suitable analytical techniques to confirm the formation of clay–polymer nanocomposites (CPN). The release profile of encapsulated PPN in CPN shows pH dependent release in simulated gastrointestinal fluid for a period of 8 h. This study suggests that the methodologies used are suitable for the synthesis of Mt based PLGA nanocomposites with high drug encapsulation efficiency and controlled drug release characteristics and indicates that the Mt–PPN–PLGA nanocomposites are supposed to be better oral controlled drug delivery system, for a highly hydrophilic low molecular weight antihypertensive drug PPN to minimize the drug dosing frequency and hence improving the patient compliance.