A steady‐state mass balance model of the polycarbonate–CO2 system reveals a self‐regulating cell growth mechanism in the solid‐state microcellular process

A simple mechanism regulating polymer mobility is demonstrated to determine initial and final growth states of solid‐state microcellular foams. This mechanism, governed by the extent of plasticization of the polymer by the dissolved gases, is examined with a mass balance model and results from foam growth experiments. Polycarbonate was exposed to CO₂, which acted as both a plasticizing gas and a physical blowing agent driving foam growth. The polycarbonate specimens were saturated to the equilibrium gas concentration at 25 °C for CO₂ pressures of 1–6 MPa in 1‐MPa increments. Equilibrated specimens were heated in a glycerin bath until thermal equilibrium was reached, and a steady foam structure was attained. Glycerin bath temperatures of 30–150 °C in 10 °C increments were examined. Using knowledge of gas solubility, the equation of state for CO₂, the effective glass‐transition temperature as a function of gas concentration, and a model for mass balance within a solid‐state foam, we demonstrate that foam growth terminates when sufficient gas is driven from the polycarbonate matrix into the foam cells. The foam cell walls freeze at the elevated bath temperature because of gas transport from the polycarbonate matrix and the associated rise in the polymer glass‐transition temperature to that of the heated bath. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 868–880, 2001     

Solid‐state microcellular and nanocellular polysulfone foams

In this article, we report on the process for creating microcellular and nanocellular polysulfone (PSU) foams. Microcellular foams with cell size up to 8 µm and nanocellular foams with cell size in the range of 20–30 nm were created. A range of CO₂ concentration was achieved by varying saturation temperature, from 5% at 60 °C to 14.7% at ?10 °C. The CO₂ concentration has a strong influence on the cellular structure. There exists a critical concentration window, between 10.7% and 12.3%, within which cell nucleation densities increase rapidly and cell sizes drop from micrometer range to below 1 µm into the nanometer range. Nanofoams with cell nucleation densities exceeding 10¹⁵ cells/cm³ and void fraction of up to 48% are achieved. At the high CO₂ concentration region, the change from closed nanocellular structure to bicontinuous nanoporous structure is observed. Also, nanostructures on the cell wall of microcells are observed and believed to be formed via stress‐induced nucleation/spinodal decomposition. The PSU nanofoams produced in this study present an opportunity to produce polymer nanofoams with a relatively high service temperature. The ability to create cells of different length scales provides an opportunity to study the effect of cell size on the foams properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 975–985     

Enhanced Electroreduction of Carbon Dioxide to Methanol Using Zinc Dendrites Pulse‐Deposited on Silver Foam

The electrocatalytic CO₂ reduction reaction (CO₂RR) can dynamise the carbon cycle by lowering anthropogenic CO₂ emissions and sustainably producing valuable fuels and chemical feedstocks. Methanol is arguably the most desirable C₁ product of CO₂RR, although it typically forms in negligible amounts. In our search for efficient methanol‐producing CO₂RR catalysts, we have engineered Ag‐Zn catalysts by pulse‐depositing Zn dendrites onto Ag foams (PD‐Zn/Ag foam). By themselves, Zn and Ag cannot effectively reduce CO₂ to CH₃OH, while their alloys produce CH₃OH with Faradaic efficiencies of approximately 1 %. Interestingly, with nanostructuring PD‐Zn/Ag foam reduces CO₂ to CH₃OH with Faradaic efficiency and current density values reaching as high as 10.5 % and ?2.7 mA cm^?2, respectively. Control experiments and DFT calculations pinpoint strained undercoordinated Zn atoms as the active sites for CO₂RR to CH₃OH in a reaction pathway mediated by adsorbed CO and formaldehyde. Surprisingly, the stability of the *CHO intermediate does not influence the activity.     

Bimetallic Ni–Co‐based metal–organic framework: An open metal site adsorbent for enhancing CO2 capture

An open metal site framework named UTSA‐16 was synthesized and modified as a high‐capacity adsorbent for reversible CO₂ capture. Partial substitution of intrinsic Co²⁺ sites of UTSA‐16 with Ni²⁺ centres was realized in the molar composition range 0–75% Ni with the aim of increasing CO₂ uptake. Synthesized bimetallic Nix‐UTSA‐16 (x = 0, 20, 50, 75) materials were characterized using various techniques to assess the influence of chemical composition on CO₂ binding affinity and any subsequent physical change in morphology, crystal size and porosity on the total uptake. Experimental isotherm adsorption studies showed the following trend for CO₂ adsorption capacity employing the Nix‐UTSA‐16 series: Ni20‐UTSA‐16 > UTSA‐16 > Ni50‐UTSA‐16 > Ni75‐UTSA‐16. According to the dynamic breakthrough CO₂ profiles measured for a mixture of CO₂ and CH₄ (15/85 molar ratio), Ni20‐UTSA‐16 exhibited 2 times the breakthrough time with 1.5 times the loading capacity at 75 Nml min^?1 feed flow rate, compared to the parent UTSA‐16. In addition, the Ni20‐UTSA‐16 bimetallic metal–organic framework exhibited lower isosteric heat of adsorption compared to UTSA‐16 (ΔH_ave = 28.54 versus 46.85 kJ mol^?1). As a result, more than 95% of its capacity was restored by applying a partial vacuum for only 1 h at room temperature without involving any other time‐ and energy‐consuming regenerative step.     

Foaming of trans‐polyisoprene using N2 as the blowing agent

Foaming of trans‐1,4‐polyisoprene (TPI) polymer was carried out through a batch process using nitrogen (N₂) as the blowing agent. TPI vulcanizates having varying crosslink densities were prepared by varying crosslinking agent content and curing time. The vulcanizates were then saturated with N₂ inside a pressure vessel at a pressure of 14 MPa and varying temperatures for 5 hours before effecting the foaming by rapidly quenching the pressure. The effects of varying the crosslinking agent content, silica filler content, and precuring time of the vulcanizates and the effects of varying the gas saturation temperature of foaming on the cell characteristics and physical properties of the foam prepared were investigated. The cells of the TPI foams had a spherical, closed structure. The density, expansion ratio, cell size, cell density, and tensile properties of the foams varied with varying crosslink density of the TPI vulcanizates as well as the saturation temperature of foaming. The important effects of crosslink density and saturation temperature on the N₂ solubility in the TPI matrix and thus on the foam expansion were discussed. The silica filler was found to be acting as a cell nucleating agent and reinforcing filler for the TPI foams.     

Contribution of Polymer‐Solvent Interactions to Dynamics of Linear Polymers in Dilute Solutions

In this work a theoretical approach to dynamics of linear vinyl polymers in dilute solutions of high viscosity solvents is presented. The calculations for the relaxation time spectra, polymer intrinsic viscosity [η (ω)], complex elastic modulus G*(ω), total intrinsic viscosity [η^T (ω)] and specific heat capacity C (ω) were carried out in the non‐free‐draining limits. The relaxation time spectrum calculated for dynamics of low frequency modes exhibits a Rouse‐like character. Its position and shape corresponds to the ultrasonic relaxation time spectrum observed in the system at 10⁶ Hz. On the other hand, the relaxation time spectrum associated with moderate frequency mode dynamics is narrower and typical for ultrasonic relaxation observed at 10⁷ Hz. The polymer intrinsic viscosity [η (ω)] and elastic modulus G*(ω) are shown to be represented by the model within a low‐frequency range. In turn, the specific heat capacity C (ω) is displayed as a representation of the model in the acoustic region mentioned above. In the high‐frequency range the dynamics is described by the total intrinsic viscosity [η^T (ω)] tending to a plateau where the value is equal to the sum of the single‐bead intrinsic viscosity [η_N] and effective solvent viscosity [η_eff].     

Room temperature processable heat‐resistant epoxy‐oxazolidone‐based syntactic foams

Syntactic foams based on oxazolidone‐modified epoxy resin using glass microballoons as reinforcing filler with varying densities were processed. The influence of various grades of microballoons and their concentration on the mechanical, thermal, thermomechanical, and flammability characteristics were investigated. The effect of temperature on the compressive strength with density was monitored in detail. By incorporating the microballoons, T_g of the syntactic foam increased from 90 °C to 115 °C. Thermal conductivity was found to decrease from (0.064 to 0.056 W/(m·K)) in conjunction with decreasing resin to filler ratio. In the case of composites filled with K25 alone, the creation of large voids due to less effective packing between the microballoons led to lower thermal conductivity. The specific heat of the different composites was in the range of 0.32 to 0.44 cal/g/°C, and the coefficient of thermal expansion was in the range of 13.2 to 17.4 × 10⁻⁶/°C with limiting oxygen index of 28% to 33%.     

Elevated ductility,optical, and air barrier properties of poly (butyleneadipate‐co‐terephthalate) bio‐based films via novel thermoplastic starch feature

It is important to develop high performances biodegradable polymers to eliminate the “white pollution” evoked by petroleum‐based polymer. Thermoplastic starch (TPS) with nano‐ellipse configuration was fabricated to reinforce the performances of poly (butylene adipate co‐terephthalate) (PBAT) biocomposites. Effects of tartaric acid (TA) (0.5% wt) on the structure of TPS and compatibility for PBAT were evaluated by Fourier‐transform infrared spectroscopy (FTIR), viscosity and rheological measurement, dynamic mechanical analysis (DMA) and scanning electron microscope (SEM), respectively. They revealed that TA reduced the molecular weight of starch and shear viscosity of TPS were beneficial for TPS dispersing in PBAT matrix with 184‐nm averaged diameter. PBAT/TPS‐TA (70:30 wt%) biocomposite films were blew with different blow‐up ratio. The morphology of films presented that nano‐TPS‐TA wrapped in the PBAT matrix and deformed from ball to capsule feature without agglomeration. Compared with those of PBAT film, the increment in elongation at break of PBAT/TPS‐TA film was 100%. The air permeability and UV‐VIS transmittance of PBAT/TPS‐TA films decreased from 6.92 × 10^?9 to 3.72 × 10^?9 cm³·cm·cm^?2 s^?1 Pa^?1 and 47.6% to 23.5%, respectively. This study proposed a facile approach to fabricate low‐cost PBAT films with significant improved mechanical, optical, and air barrier properties for commercial application. Mechanism for nanoparticles of TPS‐TA motivated the elevated performances was proposed, synchronously.     

Synthesis,characterization, and gas permeation properties of adamantane‐containing polymers of intrinsic microporosity

A new bis(catechol) monomer, namely, 4,4′‐((1r,3r)‐adamantane‐2,2‐diyl)bis(benzene‐1,2diol) (THADM) was synthesized by condensation of 2‐adamantanone with veratrole followed by demethylation of the formed (1r,3r)‐2,2‐bis(3,4 dimethoxyphenyl)adamantane. Polycondensation of THADM and various compositions of THADM and 5,5,6′,6′‐tetrahydroxy‐3,3,3′,3′‐tetramethylspirobisindane was performed with 2,3,5,6‐tetrafluoroterephthalonitrile (TFTPN) to obtain the homopolymer and copolymers. These polymers demonstrated good solubility in common organic solvents such as dichloromethane, chloroform, and tetrahydrofuran and could be cast into tough films from their chloroform solutions. GPC analysis revealed that number average molecular weights of polymers were in the range 48,100–61,700 g mol⁻¹, suggesting the formation of reasonably high molecular weight polymers. They possessed intrinsic microporosity with Brunauer‐Emmett‐Teller (BET) surface area in the range 703–741 m² g⁻¹. Thermogravimetric analysis of polymers indicated that 10% weight loss temperature was in the range 513–518 °C demonstrating their excellent thermal stability. THADM‐based polymer of intrinsic microporosity (PIM) showed P(CO₂) = 1080, P(O₂) = 232 and appreciable selectivity [α(CO₂/CH₄) = 22.6, α(CO₂/N₂) = 26.7, and α(O₂/N₂)= 5.7]. The gas permeability measurements revealed that with increase in the content of adamantane units in PIMs, selectivity increased and permeability decreased, following the trade‐off relationship. The gas separation properties of PIMs containing adamantane units were located close to 2008 Robeson upper bound for gas pairs such as CO₂/CH₄, CO₂/N₂, H₂/N₂, and O₂/N₂. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 16–24     

β‐Cyclodextrin‐modified three‐dimensional graphene oxide‐wrapped melamine foam for the solid‐phase extraction of flavonoids

A new three‐dimensional graphene oxide‐wrapped melamine foam was prepared and used as a solid‐phase extraction substrate. β‐Cyclodextrin was fabricated onto the surface of three‐dimensional graphene oxide‐wrapped melamine foam by a chemical covalent interaction. In view of a specific surface area and a large delocalized π electron system of graphene oxide, in combination with a hydrophobic interior cavity and a hydrophilic peripheral face of β‐cyclodextrin, the prepared extraction material was proposed for the determination of flavonoids. In order to demonstrate the extraction properties of the as‐prepared material, the adsorption energies were theoretically calculated based on periodic density functional theory. Static‐state and dynamic‐state binding experiments were also investigated, which revealed the monolayer coverage of flavonoids onto the β‐cyclodextrin/graphene oxide‐wrapped melamine foams through the chemical adsorption. ¹H NMR spectroscopy indicated the formation of flavonoids–β‐cyclodextrin inclusion complexes. Under the optimum conditions, the proposed method exhibited acceptable linear ranges (2–200 μg/L for rutin and quercetin‐3‐O‐rhamnoside; 5–200 μg/L for quercetin) with correlation coefficients ranging from 0.9979 to 0.9994. The batch‐to‐batch reproducibility (n = 5) was 3.5–6.8%. Finally, the as‐established method was satisfactorily applied for the determination of flavonoids in Lycium barbarum (Goji) samples with relative recoveries in the range of 77.9–102.6%.     

Effect of compressed CO2 on crystallization and melting behavior of isotactic polypropylene

Compressed gases such as CO₂ above their critical temperatures provide a highly tunable technique that has been shown to induce changes in phase behavior, crystallization kinetics and morphology of the polymers. Gas induced plasticization of the polymer matrix has been studied in a large number of polymers such as polystyrene, and poly(ethylene terephathalate). The knowledge of polymer–gas interactions is fundamental to the study of phenomena such as solubility and diffusivity of gases in polymers, dilation of polymers and in the development of applications such as foams and barrier materials.In this paper, we describe the interactions of compressed CO₂ with isotactic polypropylene (PP). Crystallization of various PPs in presence of compressed CO₂ was evaluated using a high pressure differential scanning calorimeter (HPDSC). CO₂ plasticized the polymer matrix and decreased the crystallization temperature, T_c by ∼8 °C for PP at a pressure of 650 psi CO₂. The decrease as a function of pressure was −0.173 °C/bar and did not change with the molecular architecture of PP. Both crystallization kinetics and melting behavior are evaluated.Since solubility and diffusivity are important thermodynamic parameters that establish the intrinsic gas transport characteristics in a polymer, solubility of CO₂ in PP was measured using a high-pressure electrobalance and compared with cross-linked polyethylene. At 50 °C, solubility followed Henry’s law and at a pressure of 200 psi about 1% CO₂ dissolved in PP. Similar solubility was achieved in PE at a pressure of 160 psi. Higher solubility of CO₂ in PE is attributed to its lower crystallinity and lower T_g, than PP. Diffusion coefficients were calculated from the sorption kinetics using a Fickian transport model. Diffusivity was independent of pressure and PE showed higher diffusivity than PP. Preliminary foaming studies carried out using a batch process indicate that both PP and PE can be foamed from the solid state to form microcellular foams. Cell size and cell density were ∼10 μm and 10⁸ cells/cm³, respectively in PE. Differences in morphology between the foams for these polymers are attributed to the differences in diffusivity.     

Preparation of ZnO nanoparticle‐reinforced polyamide 6 composite by in situ‐coproduced method and their properties

Polyamide 6/ZnO nanocomposites (noted as PA6/ZnO) were prepared by an in situ co‐producing method, during which Zn₂(OH)₂CO₃ decomposed into nano‐ZnO in the process of the opening‐ring polymerization of caprolactam at high temperature. Transmission electron microscopy, X‐ray diffraction, thermogravimetric analysis, and differential scanning calorimetry were used to analyze the size and dispersive properties of nano‐ZnO, the crystallization and melting properties, the thermal properties, and crystal structure of PA6/ZnO composite, respectively. The results showed that the nano‐ZnO derived from Zn₂(OH)₂CO₃ via in situ polymerization of PA6‐ZnO was uniformly dispersed in PA6 matrix. However, the overall nano‐ZnO crystallization rate and crystal size in the PA6 matrix were hindered by the bulky PA6 molecular chains. The mechanical properties were evaluated using universal tensile and impact testing instruments. The results revealed that PA6/ZnO composite with 0.2% nano‐ZnO content possessed excellent tensile strength, enhanced by 75% in comparison with the pure PA6. The nano‐ZnO had little influence on the impact strength of PA6. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57, 165–170     

Ultrasonic‐assisted synthesis and biological evaluation of a nano‐rod diorganotin phosphonic diamide: Precursor for the fabrication of SnP2O7 nano‐structure

Nanorods of a diorganotin phosphonic diamide with formula [Sn(CH₃)₂(Cl)₂(L)₂]{L = C₆H₅(O)P(NHC₆H₁₁)₂} have been synthesized by sonochemical processes at different concentrations without any surfactant or capping agent. The structure and morphology of the prepared complex were investigated by using SEM‐EDAX, XRD, DLS, UV–Vis and FT‐IR spectroscopy. Nanoparticles with well‐defined rod shapes and sizes in the range 30–40 nm have been obtained. Also bulk form of the titled complex was synthesized and characterized by ¹H, ¹³C, ³¹P, ¹¹⁹Sn NMR, UV–Vis and FT‐IR spectroscopy and compared with its nano‐size. The thermal stabilities at bulk and nano‐size scale have been studied by thermal gravimetric (TG) and differential thermal analysis (DTA). Further, SnP₂O₇ nanoparticles were synthesized by direct calcination at 730 °C under air atmosphere and characterized using XRD, SEM, and TEM. From XRD measurements, we determined the mean size of the crystallites about 27.4 nm. It is found that the size and morphology of the tin pyrophosphate nano‐structures are dependent upon the particles size of precursor compound as well. Two different forms of metal coordination compound (1a, 1b) and the corresponding ligand (L) were screened for their antibacterial activity against the selected Gram‐positive and Gram‐negative bacteria, showing bactericidal activity for complexes 1a and 1b. In vitro cytotoxicity of compounds was studied against human carcinoma cell lines, A2780 (ovarian cancer) and PC‐3 (prostate cancer). Results indicated that 1a and 1b possess relatively strong cytotoxic activity against cancer cells with IC₅₀ values ranging from 93.2 to 376.2 μM for two exposure time (24 and 48 h).     

Kinetics study of oil sorption with open‐cell polypropylene/polyolefin elastomer blend foams prepared via continuous extrusion foaming

The objective of the present work was to study the sorption kinetics of open‐cell polypropylene/polyolefin elastomer (PP/POE) blend foams. First, open‐cell PP/POE foams of different cell structures were prepared by controlling the foaming temperature via a continuous extrusion foaming process. Second, the effect of the cell structures on the sorption process, rate, and capacity was studied. Pseudo‐first order and pseudo‐second order models were applied to study the sorption kinetics of the PP/POE foams for cyclohexane. Third, the sorption rate and sorption capacity by both volume and weight of the PP/POE foam for different oils and solvents were studied to show how the intrinsic properties of the testing oils and solvents affected the sorption performance. The results showed that the sorption with the PP/POE foams followed the pseudo‐second order kinetics model. Both the cell structures of the foams and the intrinsic properties of the testing oils and solvents affected the sorption performance. For the same testing oil, a higher open‐cell content in the foam was favorable for a higher sorption rate, and a higher void fraction was favorable for a higher sorption capacity. For the same foam, a lower viscosity of the testing oil was favorable for a higher sorption rate. The sorption capacity by volume was closely related to the viscosity of the testing oil, while both the viscosity and the density of the testing oil determined the sorption capacity by weight.     

Effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene compatibilizer on the recycled polypropylene and recycled high‐impact polystyrene blends

The recycled polypropylene/recycled high‐impact polystyrene (R‐PP/R‐HIPS) blends were melt extruded by twin‐screw extruder and produced by injection molding machine. The effects of polystyrene‐b‐poly(ethylene/propylene)‐b‐polystyrene copolymer (SEPS) used as compatibilizer on the mechanical properties, morphology, melt flow index, equilibrium torque, and glass transition temperature (T_g) of the blends were investigated. It was found that the notch impact strength and the elongation at break of the R‐PP/R‐HIPS blends with the addition of 10 wt% SEPS were 6.46 kJ/m² and 31.96%, which were significantly improved by 162.46% and 57.06%, respectively, than that of the uncompatibilized blends. Moreover, the addition of SEPS had a negligible effect on the tensile strength of the R‐PP/R‐HIPS blends. Additionally, the morphology of the blends demonstrated improved distribution and decreased size of the dispersed R‐HIPS phase with increasing the SEPS content. The increase of the melt flow index and the equilibrium torque indicated that the viscosity of the blends increased when the SEPS was incorporated into the R‐PP/R‐HIPS blends. The dynamic mechanical properties test showed that when the content of SEPS was 10 wt%, the difference of T_g decreased from 91.72°C to 81.51°C. The results obtained by differential scanning calorimetry were similar to those measured by dynamic mechanical properties, indicating an improved compatibility of the blends with the addition of SEPS.     

Lanthanum phenylphosphonate–based multilayered coating for reducing flammability and smoke production of flexible polyurethane foam

In the present work, lanthanum phenylphosphonate (LaPP)–based multilayered film was fabricated on the surface of flexible polyurethane (PU) foam by layer‐by‐layer self‐assembled method. The successful deposition of the coating was confirmed by scanning electron microscopy (SEM) and energy‐dispersive X‐ray (EDX). Subsequently, the thermal decomposition and burning behavior of untreated and treated PU foams were investigated by thermogravimetric analysis (TGA) and cone calorimeter, respectively. The TGA results indicated that T_max2 of treated PU foams were increased by approximately 15°C to 20°C as compared with untreated PU foam. The peak heat release rate (PHRR) and total heat release (THR) of PU‐6 (with 19.5 wt% weight gain) were 188 kW/m² and 20.3 MJ/m², with reductions of 70% and 15% as compared with those of untreated PU foam, respectively. Meanwhile, the smoke production of treated PU foam was suppressed after the construction of LaPP‐based coating.     

Dehydrogenation of Isobutane to Isobutene with Carbon Dioxide over SBA‐15‐Supported Chromia‐Ceria Catalysts

A series of SBA‐15‐supported chromia‐ceria catalysts with 3% Cr and 1%–5% Ce (3Cr‐Ce/SBA) were prepared using an incipient wetness impregnation method. The catalysts were characterized by XRD, N₂ adsorption, SEM, TEM‐EDX, Raman spectroscopy, UV–vis spectroscopy, XPS and H₂‐TPR, and their catalytic performance for isobutane dehydrogenation with CO₂ was tested. The addition of ceria to SBA‐15‐supported chromia improves the dispersion of chromium species. 3Cr‐Ce/SBA catalysts are more active than SBA‐15‐supported chromia (3Cr/SBA), which is due to a higher concentration of Cr⁶⁺ species present on the former catalysts. The 3Cr‐3Ce/SBA catalyst shows the highest activity, which gives 35.4% isobutane conversion and 89.6% isobutene selectivity at 570 °C after 10 min of the reaction.     

Photo‐Fenton and Riboflavin‐photosensitized Processes of the Isoxaflutole Herbicide

The proherbicide Isoxaflutole (IXF) hydrolyzes spontaneously to diketonitrile (DKN) a phytotoxic compound with herbicidal activity. In this work, the sensitized degradation of IXF using Riboflavin (Rf), a typical environmentally friendly sensitizer, Fenton and photo‐Fenton processes has been studied. The results indicate that only the photo‐Fenton process produces a significant degradation of the IXF. Photolysis experiments of IXF sensitized by Riboflavin is not a meaningful process, IXF quenches the Rf excited triplet (³Rf*) state with a quenching rate constant of 1.5 · 10⁷ m ^?1 s^?1 and no reaction is observed with the species O₂(¹Δ_g) or ${\mathrm{O}}_2^{·?}$ generated from ³Rf*. The Fenton reaction produces no changes in the IXF concentration. While the photo‐Fenton process of the IXF, under typical conditions, it produces a degradation of 99% and a mineralization to CO₂ and H₂O of 88%. A rate constant value of 1.0 × 10⁹ m ^?1 s^?1 was determined for the reaction between IXF and HO˙. The photo‐Fenton process degradation products were identified by UHPLC‐MS/MS analysis.     

Microcellular foaming of polylactide and poly(butylene adipate‐co‐terphathalate) blends and their CaCO3 reinforced nanocomposites using supercritical carbon dioxide

Foamed polylactide (PLA), PLA–PBAT (poly (butylene adipate‐co‐terphathalate)) blend and their composites with CaCO₃ were prepared in a batch process using supercritical carbon dioxide (CO₂) at 12 MPa and 45°C. The solubility of CO₂ and its diffusion patterns in different PLA samples was investigated. PLA systems had a relatively high CO₂ solubility related to the carboxyl groups. CO₂ desorption behaviors in PLA systems first followed the Fickian diffusion mechanism in short time and then decreased slowly to a plateau. The addition of both PBAT and CaCO₃ into PLA impeded the desorption of CO₂. In the presence of second phase PBAT, nanoparticles CaCO₃ and dissolved CO₂, the PLA crystallization behavior investigated by DSC technique was greatly changed. As the desorption time increased, the gas induced crystallinity slightly decreased in consequence of less CO₂ content in each system and thus less plasticization effect. The cell morphology of foamed PLA and PLA composites showed interesting microstructure patterns. The prepared pure PLA foam exhibits a typical bimodal structure because of the foaming in both the amorphous and crystalline zones. With PBAT and CaCO₃ into PLA, the composite foam presented significant increase in cell uniformity and cell density. With less CO₂ content in each PLA sample, the cell structure showed interesting variation. Pure PLA foam presented transition from bimodal structure to more uniform cell structure with decreased cell density. In contract, PLA–PBAT foam show unfoamed regions because of none CO₂ left in the separated PBAT phase. Copyright © 2016 John Wiley & Sons, Ltd.     

Ligand‐free palladium‐catalyzed tandem pathways for the synthesis of 4,4‐diarylbutanones and 4,4‐diaryl‐3‐butenones under microwave conditions

Two efficient Pd‐catalyzed tandem pathways for the synthesis of 4,4‐diaryl‐2‐butanones and 4,4‐diaryl‐3‐buten‐2‐ones were elaborated. The first step in both procedures was the Heck coupling of methyl vinyl ketone (MVK) and various aryl iodides leading to 4‐aryl‐3‐buten‐2‐one with the yield of up to 92% in 1 hr. The second step performed with the same catalyst and a new portion of aryl iodide in the presence K₂CO₃ as a base produced 4,4‐diaryl‐3‐buten‐2‐ones in high yield. Reaction selectivity changed completely to saturated 4,4‐diaryl‐2‐butanones, reductive Heck products, when a tertiary amine was used instead of K₂CO₃. Due to the application of microwave irradiation (MW), the desired products were obtained in high yield in a short time (4 hr), using 0.5 mol% of the Pd (OAc)₂ catalyst without additional ligands.