Microphase separated structures in the solid and molten states of double-crystal graft copolymers of polyethylene and poly(ethylene oxide)

Transitions from one microphase separated structure in the solid state to a different one in the molten state in polyethylene-graft-poly(ethylene oxide) copolymers, PE-g-PEO, were investigated by variable temperature X-ray scattering measurements and thermal analyses. Small-angle X-ray scattering patterns from polymers with PEO grafts with 25, 50 and 100 ethylene oxide (EO) units show that the polymer passes through three distinct structures at ～10 nm length scales with increase in temperature (T): lamellar structures of PE and PEO at T < T_m^PEO, PE lamellae surrounded by molten PEO at T_m^PEO < T < T_m^PE, and microphase separated structures at T > T_m^PE when both PE and PEO are molten (T_m refers to the melting temperature). These phase transformations also occur during cooling but with hysteresis. Crystalline phases of PEO side chains and PE main chains could be identified in the wide-angle X-ray diffraction profiles indicating that the PE backbone and PEO grafts crystallize into separate domains, especially with longer grafted chains (50 and 100 units). At EO segment lengths > 50, PEO shows the expected increase in melting and crystallization temperatures with the increase in the grafted chain length. PE does not affect T_m^PEO but does decrease the onset of crystallization upon cooling. PEO grafts result in fractionation of PE, decrease the melting point of PE and increase the undercooling for the onset of crystallization of PE.     

In situ FTIR micro-spectroscopy to investigate polymeric fibers under supercritical carbon dioxide: CO2 sorption and swelling measurements

An original experimental set-up combining a FTIR (Fourier Transformed InfraRed) microscope with a high pressure cell has been built in order to analyze in situ and simultaneously the CO₂ sorption and the polymer swelling of microscopic polymer samples, such as fibers, subjected to supercritical carbon dioxide. Thanks to this experimental set-up, we have determined as a function of the CO₂ pressure (from 2 to 15 MPa) the CO₂ sorption and the polymer swelling at T = 40 °C of four polymer samples, namely PEO (polyethylene oxide), PLLA (poly-l-lactide acid), PET (polyethylene terephtalate) and PP (polypropylene). The quantity of CO₂ sorbed in all the studied polymers increases with pressure. PEO and PLLA display a significant level of CO₂ sorption (20 and 25% respectively, at P = 15 MPa). However, we observe that a lower quantity of CO₂ can be sorbed into PP and PET (7 and 8% respectively, at P = 15 MPa). Comparing their thermodynamic behaviors and their intrinsic properties, we emphasize that a high CO₂ sorption can be reach if on one hand, the polymer is able to form specific interaction with CO₂ in order to thermodynamically favor the presence of CO₂ molecules inside the polymer and on the other, displays high chains mobility in the amorphous region. PLLA and PEO fulfilled these two requirements whereas only one property is fulfilled by PET (specific interaction with CO₂) and PP (high chains mobility). Finally, we have found that for a given CO₂ sorption, the resulting swelling of the polymer depends mainly on its crystallinity.     

A novel,conjugated polymer containing fluorene,pyridine and unsymmetric carbazole moieties: Synthesis,protonation and electrochemical properties

An optically active, conjugated polymer bearing unsymmetric pendant carbazole chromophores was prepared via the Suzuki coupling of 9,9-dioctylfluorene-2,7-diboronic acid and a novel pyridine-containing compound. The polymer had a T_g of 192 °C and T_d10 at 437 °C under a nitrogen atmosphere and exhibited absorption bands at 320–400 nm and displayed an additional absorption bands at 380–480 nm after protonation with aq. HCl solution. The photoluminescence of the polymer shifted from 360–460 nm to 460–560 nm after protonation and the photoluminescence quantum yield of the polymer in THF solution was 0.88. The emission color of the polymer film changed from blue (439 nm) to yellow (551 nm) under an applied bias voltage of 2.5 V.     

Aggregation behavior of two-arm fullerene-containing poly(ethylene oxide)

A water-soluble two-arm fullerene-containing poly(ethylene oxide) (PEO) was synthesized through isocyanate-hydroxy condensation reaction with fullerenol as a molecular core and characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetry, and matrix-assisted laser desorption ionization time of flight mass spectrometry. The aggregation behavior of the resulting amphiphilic polymer in water, THF, and DMF, was studied by gel permeation chromatography, laser light scattering, and transmission electron microscopy. The polymer forms spherical aggregates with an aggregation number around 540-1020.     

The properties of hydroxyapatite ceramic coatings produced by plasma electrolytic oxidation

Calcium phosphate coatings produced on the surface of Ti6Al4V by plasma electrolytic oxidation (PEO) using different concentrations of hydroxyapatite (HA) in a 0.12 M Na₃PO₄ (NAP) electrolyte solution was investigated. It was found that the amount of calcium phosphate particles infiltrated into the coating layer as well as the thickness and the surface roughness of the coating increased with increasing HA concentration. The porosity of the ceramic coatings indicated an inverse relationship with the concentration of HA particles dispersed in the NAP solution. The result also demonstrates that higher scratch adhesive strength was achieved using 1.5 g/L HA solution, producing a critical load of 2099 mN, while 0 g/L HA only produced a critical load of 1247 mN. The adhesion becomes independent of thickness when the concentration of HA exceeds 1.5 g/L. The failure of the coating was characterized by large periodic hemispherical chipping, while intermittent delamination was noticed with the coating embedded with HA particles. This study demonstrate the viability of using PEO to produce a thin layer of HA ceramic coating on Ti6Al4V suitable for biomedical applications.     

New pathway for the preparation of pyrochlore Nd2Zr2O7 nanoparticles

Pyrochlore Nd₂Zr₂O₇ nanoparticles were prepared by complex-precipitation in aqueous media, followed by calcination in MgO matrix and subsequent dissolution processing. A suite of characterization techniques, including X-ray diffraction, Raman, TEM, SEM, dynamic light scattering, and nitrogen sorption, was employed to investigate the structure and particle size of the synthesized nano materials. Results show that calcination at 1200 °C for 20 h forms Nd₂Zr₂O₇ with pyrochlore structure. The matrix phase (MgO) had no effect on the formation of pyrochlore phase. The MgO phase was readily removed by dissolution at 0.5 M HNO₃ aqueous solution; and the remaining pyrochlore Nd₂Zr₂O₇ nanoparticles had a diameter of approximately 200 nm estimated by TEM and approximately 550 nm determined by light scattering due to slight aggregation. The bulk density of the pelletized powder reached approximately 99% of theoretical value, after uniaxial pressing at 2.0–2.5 MPa and sintering at 1400 °C for 48 h.     

Synthesis and structure of a copper sulfate/kinked organodiimine coordination polymer entraining “infinite” decorated water chains with C14 classification

The 1D chain coordination polymer {[Cu(SO₄)(dpmd)₂] · 8H₂O} (1, dpmd = 4,4′-dipyridylmethanediol) has been prepared by a solution phase method and characterized by single-crystal X-ray diffraction, IR and thermogravimetric analysis. The dpmd ligand was formed in situ from 4,4′-dipyridylketone. Decorated 1D water molecule chains with a very rare C14 classification co-crystallized and were stabilized within the coordination polymer matrix.     

Three Ln(III)-2,3,5-trichlorobenzoate coordination polymers (Ln = Tb,Ho and Er): Syntheses,structures and magnetic properties

Three novel lanthanide polymers, [Ln(III)(L)₃EtOH]_n (Ln = Tb(1), Ho(2), Er(3), HL = 2,3,5-trichlorobenzoic acid), have been solvothermal synthesized and characterized by single-crystal X-ray diffraction, infrared spectroscopy and element analyses. The three polymers crystallize in triclinic space group P-1. The Ln(III) ions are in turn bridged by double and quadruple carboxylate of L⁻ ligands to form one-dimensional (1D) chains. Magnetic studies reveal that polymer 1 demonstrates dominant ferromagnetic behavior, polymer 2 shows antiferromagnetic behavior, and polymer 3 present spin-canting behavior.     

Open circuit voltage increase by substituted spacer and thieno[3,4-c]pyrrole-4,6-dione for polymer solar cells

We reported on two donor polymers containing thieno[3,4-c]pyrrole-4,6-dione(TPD) derivatives as electron withdrawing units for organic photovoltaics (OPVs). To control molecular weight and solubility of polymers, hexyl side chains are inserted to thiophene spacers. Due to the electron donating characteristic of hexyl side chains, highest occupied molecular orbital (HOMO) energy level of polymer is decreased as 0.18 eV, whereas the open circuit voltage is increased to 1.08 V. When bulk heterojunction devices were fabricated, the best PCE value of 0.360% (V_OC = 0.89 V, J_SC = 1.2 mA/cm², FF = 36.3%) under 100 mW/cm² irradiation.     

Association phenomena of a chiral perylene derivative in solution and in poly(ethylene) dispersion

In this work, the aggregation behaviour of a chiral perylene derivative, that is, N,N′-bis-(R)-(1′-phenylethyl)-perylene-3,4,9,10-tetracarboxyldiimide (R-Pery), was studied by means of ¹H NMR (including DOSY techniques), circular dichroism, UV–Vis and fluorescence spectroscopies in various conditions. The acquired data demonstrate that R-Pery tends to aggregate in pure solvents at high concentrations (>10^?5 M in DMSO and >10^?3 M in CHCl₃), whereas aggregation occurred at lower concentrations by adding a poor solvent, such as water (to DMSO) or CH₃CN (to chloroform). Interesting results were obtained studying the optical behaviour of R-Pery when dispersed into a linear low-density polyethylene matrix (LLDPE). In particular, the aggregation extent of R-Pery into LLDPE was investigated by means of UV–Vis, fluorescence and CD spectroscopies as a function of dye concentration as well as thermal stimuli. The optical responsiveness of R-Pery (both in absorption and in emission) versus moderate temperature changes (i.e., for T > 35 °C) suggests applications of polymer dispersions as smart and reversible indicators to thermal solicitations.     

A copper sulfoisophthalate dipyridylpropane coordination polymer with a new,simple 4,4,4-connected trinodal topology

The coordination polymer {[Cu₃(sip)₂(dpp)₄]·14H₂O}_n (sip = 5-sulfoisophthalate, dpp = 1,3-di(4-pyridyl)propane) was synthesized and structurally characterized by single-crystal X-ray diffraction. The crystallographically distinct copper atoms represent distinct 4-connected nodes that form a novel yet very simple 4,4,4-connected (6⁴8²)₂(6⁶) topology, which resembles a hybrid of well-known diamondoid and PtS networks. Incipient one-dimensional channels containing chains of disordered water molecules occupy 26.7% of the unit cell volume. Upon removal, the coordination polymer apohost does not permit gas absorption.     

Preparation of Pt-loaded TiO2 nanofibers by electrospinning and their application for WGS reactions

Preparation of Pt-loaded TiO₂ nanofibers and their catalytic performance for water gas shift (WGS) reactions have been explained in this work. The Pt-loaded TiO₂ nanofibers were obtained by electrospinning poly-ethylene oxide (PEO) aqueous solutions containing Ti(OH)_n slurry and Pt nanoparticles at room temperature, followed by calcination at 773 K for 4 h. The calcined nanofibers were rougher than the nanofibers of PEO/Ti(OH)_n/Pt due to the PEO degradation and oxidation of Ti(OH)_n to TiO₂. Diameters of the Pt-loaded TiO₂ nanofibers ranged between 200 and 900 nm. Catalytic activity of the Pt-loaded TiO₂ nanofibers for water gas shift (WGS) reactions was evaluated and it was observed that their activity was 5–7 times higher than that of a bulk catalyst. Such improvement is attributed to the larger surface area of the nanofiber catalyst compared to that of the bulk catalyst. To the best of our knowledge, this is the first demonstration of a synthesis of Pt-loaded TiO₂ nanofibers from a Ti(OH)_n nanoparticle slurry using electrospinning and its application to WGS reactions.     

Preparation and thermoelectric properties of MoS2/Bi2Te3 nanocomposites

MoS₂ nanosheets with size of several-hundred nanometers were prepared by a hydrothermal intercalation/exfoliation method, then MoS₂/Bi₂Te₃ composite nanopowders were prepared by a microwave-assisted wet chemical method using the MoS₂ nanosheets, TeO₂, Bi(NO₃)₃·5H₂O, KOH and ethylene glycol as raw materials. Bulk MoS₂/Bi₂Te₃ nanocomposites were prepared by hot pressing the MoS₂/Bi₂Te₃ composite nanopowders with MoS₂ nanosheet content ranging from 0 to 17 wt% at 80 MPa and 648 K in vacuum. X-ray photoelectron spectroscopy and X-ray diffraction analyses indicate that MoS₂ and Bi₂Te₃ did not react each other during the hot pressing. FESEM observation reveals that the MoS₂/Bi₂Te₃ composite samples had a more compact microstructure than the pristine Bi₂Te₃ bulk sample. The MoS₂ phase was relatively randomly dispersed in the composite. At a given temperature, the electrical conductivity of the composites increases first then decreases as the MoS₂ content increases, whereas the Seebeck coefficient of the bulk nanocomposites does not change much. A highest power factor, ~18.3 μW cm⁻¹ K⁻² which is about 30% higher than that of pristine Bi₂Te₃ sample, at 319 K has been achieved from a nanocomposite sample containing 6 wt% MoS₂.     

Anticancer therapeutic self-aggregates of sphingolipid metabolite-grafted poly(amino acid)-derivative and their enhanced intracellular delivery

Novel sphingolipid metabolite conjugated poly(amino acid)-derivative, poly-α,β-(2-hydroxylethyl l-aspartamide)-g-phytosphingosine copolymer, was designed as an anticancer prodrug-type carrier for enhanced intracellular uptake and physicochemical properties of polymeric micelle-like aggregates were evaluated. The resultant micelle-like aggregates showed a spherical shape and uniform size with a diameter less than 20 nm in an aqueous solution upon the increased number of phytosphingosine grafts. By the steady-state fluorescence of pyrene in aqueous polymer solutions, critical aggregation concentration (CAC) was obtained in the range of 0.166–0.0036 mg/ml and K_v, equilibrium partition constants of the pyrene in the self-aggregate solutions were estimated to be from 2.39 × 10³ to 1.96 × 10⁶. Phytosphingosine-grafted polymeric micelle-like aggregates as small as 20 nm were efficiently delivered into various cancer cell lines including oral, breast and colon carcinoma with the extent which is comparable to the level of targeting carrier system. The enhanced cellular uptake and anticancer therapeutic effect was evaluated by flow cytometry, confocal laser scanning microscopy (CLSM), and MTT assay.     

Scalable synthesis of carbon-embedded ordered macroporous titania spheres with structural colors

Carbon-embedded ordered macroporous titania (C-MAC TiO₂) spheres are prepared in solution by the cooperative self-assembly of polymer beads and a titania precursor within evaporative emulsions and subsequent direct carbonization. Because the highly reactive titania precursors are easily crosslinked to form gels early in evaporation before the polymer beads are self-organized, non-reactive toluene-in-formamide emulsions are used. These non-aqueous emulsions should be stable at relatively high temperatures (~80 °C) for the evaporation process. We found that amphiphilic triblock copolymers of poly(ethylene oxide) (PEO) and poly(phenylene oxide) (PPO) with longer PEO chains (Pluronic® F108 (EO₁₂₅-b-PO₆₄-b-EO₁₂₅) are required to stabilize those non-aqueous emulsions, and become more important at higher concentrations used for bulk fabrication. The carbon inside our C-MAC TiO₂ significantly suppresses strong multiple scattering from structural defects or imperfections, thus emphasizing their Bragg reflection colors.     

Polyimide/nano-TiO2 hybrid films having benzoxazole pendent groups: In situ sol–gel preparation and evaluation of properties

Polyimide/titania (PI/TiO₂) nanocomposite films have been successfully fabricated through the in situ formation of TiO₂ within a PI matrix via sol–gel method. Poly(amic acid) (PAA), which is the precursor of PI, was successfully synthesized by mixing pyromellitic dianhydride (PMDA), with equimolar amount of a diamine monomer having a pendent benzoxazole unit and two flexible ether linkages in N,N-dimethylformamide (DMF) solvent. Tetraethyl orthotitanate [Ti(OEt)₄] and acetylacetone were then added to the resulted PAA. After imidization at high temperature, PI/TiO₂ hybrid films were formed. The structure and morphology of the hybrid nanocomposites with different titania contents (0 wt%, 5 wt%, 10 wt%, and 15 wt%) were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The results indicate that the TiO₂ nanoparticles were homogeneously dispersed in the hybrid films. The thermogravimetric analysis of nanocomposites confirms the improvement in the thermal stability with the increase in the percentage of titania nanoparticle. Transmission electron microscopy showed that the nanoparticles with an average diameter of 25–40 nm were dispersed in the polymer matrix.     

Thermal dehydration of Y(TFA)3(H2O)3: Synthesis and molecular structures of [Y(μ,η1:η1-TFA)3(THF)(H2O)]1∞ · THF and [Y4(μ3-OH)4(μ,η1:η1-TFA)6(η1-TFA)(η2-TFA)(THF)3(DMSO)(H2O)] · 6THF (TFA = trifluoroacetate)

In order to obtain a better anhydrous precursor for various applications in materials science and catalysis, thermal dehydration reactions of Y(TFA)₃(H₂O)₃ (TFA = trifluoroacetate) (A) were investigated. Thermal treatment of A at different temperatures under vacuum (5 × 10^?2 mm) for several hours failed to give totally anhydrous yttrium trifluoroacetate (as indicated by IR). Two different complexes, a partially dehydrated [Y(μ,η¹:η¹-TFA)₃(THF)(H₂O)]_1∞·THF (1) and a partially hydrolyzed [Y₄(μ₃-OH)₄(μ,η¹:η¹-TFA)₆(η¹-TFA)(η²-TFA)(THF)₃(DMSO)(H₂O)] · 6THF (2), were obtained with good and moderate yield, respectively, by crystallization of two different thermally treated batches of A from THF (or THF + DMSO) at room temperature. More efficient dehydration of A could be achieved at 200 °C in a furnace, the obtained anhydrous yttrium tris-trifluoroacetate giving Y(TFA)₃(THF)₂ (3) on crystallization from THF. All the products were characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy as well as thermo-gravimetric analysis. In addition, single crystal X-ray structures are reported for 1 and 2, which show either a terminal (η¹ and η²) or bridging (μ,η¹:η¹) bonding behavior of the TFA ligand.     

Studies on physico-chemical and antibacterial properties of grafted pullulans solutions

The physico-chemical properties of three grafted pullulans (P) having linked poly(3-acrylamidopropyl)trimethylammonium chloride (pAPTAC) as side chains (P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 with 22.53, 29.05, and 34.51 (wt.%) of pAPTAC content in polymer, respectively) and possessing polyelectrolyte character were determined by light scattering analysis. All grafted pullulan aqueous solutions were tested in the presence of 0.5 M NaCl, KCl, NaNO₃ or KNO₃. The biggest associations were recorded in 0.5 M NaCl aqueous solutions for P-g-pAPTAC1, P-g-pAPTAC2 and P-g-pAPTAC3 according to the maximum values for R_g extracted from MALLS (multiangle laser light scattering) measurements. Also, the dominant conformation in salted solution of these polyelectrolytes was random coil as Debye plot analysis revealed. Antibacterial activity was tested by Kirby–Bauer diffusion method and all grafted pullulans dissolved in aqueous solutions of 0.5 M NaCl have developed inhibition zone against Staphylococcus aureus (ATCC 25923).     

The effect of solution properties on the morphology of ultrafine electrospun egg albumen–PEO composite fibers

Biocompatible composite fibers suitable for food and medical applications were electrospun from egg albumen (EA) and poly(ethylene oxide) (PEO) at a flow rate of 1.8 mL/min, at an applied voltage of 22 kV and a capillary to target distance of 15 cm. The ratio of EA to PEO dispersed in formic acid was varied from 1:0 to 1:0.1, 1:0.3, 1:0.6 and 0:1. The influence of dispersion properties such as viscosity, surface tension and electrical conductivity on the morphology of electrospun fibers was investigated. As the ratio of PEO increased, viscosity, surface tension, and conductivity decreased. Electrospun fibers had diameters of 188 ± 21, 289 ± 33, 470 ± 32 and 202 ± 20 nm for EA–PEO composite ratios of 1:0.1, 1:0.3, 1:0.6, and 0:1, respectively. Pure EA did not form fibers, but was deposited as beads instead. Results were attributed to increasing entanglement of the two polymers as the concentration of PEO in the solution increased leading to larger diameters of electrospun fibers. Compositional analysis of fibers spun from mixed dispersions using FTIR and TGA indicated that fibers were composed of both EA and PEO, but that fibers contained larger concentrations of PEO than the original dispersions. Investigation of thermal properties by DSC showed the absence of a melting point in 1:0.1 and 1:0.3 EA–PEO fibers. At an EA–PEO ratio of 1:0.6, a melting point characteristic of PEO was identified but enthalpy was significantly smaller than that of pure PEO which could possibly be attributed to molecular interactions between the two polymers.     

Synthesis and properties of some aromatic polyamides with coumarin chromophores

A novel monomer diacid, 6,6′-methylenebis{2-oxo-8-{2-[(2-oxo-2H-chromen-7-yl)oxy]acetoxy}-2H-chromene-3-carboxylic acid}, having two substituents (2-oxo-2H-chromen-7-yl)oxyacetate in the aromatic moiety, was synthesized and used in a direct polycondensation reaction with various aromatic diamines using triphenyl phosphite and pyridine as condensing agents to give a series of new aromatic polyamides with photosensitive coumarin pendent groups. Polyamide properties were investigated by DSC, TGA, GPC (gel permeation chromatographic analysis), and wide-angle X-ray scattering, viscosity and solubility measurements. The introduction of bulky side chains in the structure of aromatic polyamides led to moderate inherent viscosity values (0.40–0.87 dLg^?1) and increased solubility of these polymers in aprotic polar solvents such as NMP (N-methylpyrrolidone), DMAc, DMSO and DMF, and in less polar solvents like Py and THF. The good solubility of these polyamides was in agreement with their amorphous character as evidenced by X-ray diffraction diagrams. Gel permeation chromatography evidenced high molecular weights (49,400–63,900 gmol^?1) which allowed transparent, flexible and tough films to be cast from polymer solutions. These aromatic copolyamides showed good thermal properties associated with glass transition temperatures (Tg) in the range of 221–257 °C and the onset of decomposition in air above 390 °C. UV illumination (λ > 300 nm) of the polymer films induced crosslinking between polyamide molecules through a [2π + 2π] photocycloaddition at the CC bond of coumarin moieties. Information concerning the photoreactive property of coumarin-containing polymers was obtained by studying the changes in the UV absorption spectra and IR spectra of irradiated polymeric films.