Formation Of 3D Network Research Articles

Morphology evolution of poly(lactic acid) during in situ reaction with poly(butylenesuccinate) and ethylene‐methyl acrylate‐glycidyl methacrylate: The formation of a novel 3D star‐like structure

AbstractMorphology control of polymer alloys is an attractive topic for investigators due to its ability to improve the performance of products for years. However, it is hard to control the morphology of immiscible polymer blends during melt processing. Herein, we studied the morphology evolution of poly(lactic acid) (PLA)/poly(butylene succinate) (PBS) with the inclusion of ethylene‐methyl acrylate‐glycidyl methacrylate (EGMA). Scanning electron microscopy of both cryo‐fractured and etched cryo‐fractured samples indicates that the in situ reaction among PLA, PBS, and EGMA can induce the morphology change and result in a novel 3D star‐like structure. Rheology behaviors of the samples under different angular frequencies were used to validate the formation of 3D networks in the samples. Tensile stiffness reinforcements at both room temperature and high temperature were provided through dynamic mechanical analysis. In addition, a 10‐fold improvement in impact strength is also monitored by the unnotched impact test to indicate the superior toughening effect. Furthermore, the crystalline behavior and thermal properties of the blends were also studied. It is believed that our work not only gives a deeper understanding of the reaction‐induced morphology evolution of the PLA/PBS/EGMA blends but also reveals an avenue toward morphology control by melt processing.

Intermolecular Interactions between Halogen-Substituted p-Benzoquinones and Halide Anions: Anion-π Complexes versus Halogen Bonding.

Intermolecular interactions between halo-substituted p-benzoquinones (BQ) and halide anions were examined in solution, solid-state and/or in silico. While X-ray crystallography revealed only halogen bonding (XB) between tetraiodo-p-benzoquinone (I4 Q) and halides, the results of a UV-Vis study in solutions were consistent with the formation of 1 : 1 anion-π complexes. DFT computations showed that the anion-π complexes of halides with most halo-substituted BQ molecules were more stable (by 2-7 kcal/mol) than their XB analogues, but the stabilities of different complexes of I4 Q were essentially the same. Thus, the structural features of the co-crystals with I4 Q were related to multicenter XB interactions between BQs and halides, thus leading to the formation of 3D networks. The observation of anion-π complexes in solutions was attributed to their higher molar absorptivity (by more than an order of magnitude) than that of their XB analogues. Overall, the stabilities of anion-π and XB complexes between BQs and halides were well correlated with the values of highest electrostatic potentials on the surfaces of BQ molecules when their polarizations were taken into account.

Dimension Control in Mixed Linker Metal-Organic Frameworks via Adjusting the Linker Shapes.

In this context, we describe a novel method to control the dimensionality and, further, the morphology in three mixed linker metal-organic frameworks (MOFs) TMU-70, TMU-71, and TMU-49 via altering the linker shapes. The compatibility between the shape of linkers used in the mixed linker framework, specifically linker angles, can directly affect the dimensionality of the resulting networks from 2D to 3D. Using incompatible linkers (one bent and one linear) together with binodal SBU directed the structure to form 2D networks, while 3D networks were obtained through applying linkers with the same shape. Further, the 2D and 3D MOFs were fabricated through the coordination modulation strategy. The impact of various modulators on the size and morphology of the structures has been examined. The 2D MOFs produced only nanorods through application of different capping agents owing to their preferred crystal growth, while the 3D networks led to rod and plate morphologies. Also, the catalytic performance of MOFs in an aldol-type condensation reaction was estimated. High and fast catalytic activity is detected in nanoscale rod-shaped catalysts.

Fabrication of high thermal stable cured novolac/Cloisite 30B nanocomposites by chemical modification of resin structure

Cloisite 30B as a modified kind of nanoclay was utilized for the formation of 3D network based on novolac resin with high thermal stable properties. Two types of phenolic resins including neat novolac (NR) and modified novolac resin were used to create a compatible matrix with nanoclay. For this purpose, NR modified with (3‐chloropropyl)triethoxysilane (CPTES) to form SiNR. For improvement of thermal behaviors, Cloisite 30B was dispersed in matrix via ultrasonic waves and cured with hexamethylenetetramine (HMTA) to form 3D network. X‐ray diffraction (XRD) analysis was used to measure the d‐spacing in intercalated systems and results indicated the optimum amount of clay for appropriate thermal properties. Investigation of the thermal properties of the samples by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) showed that the presence of Cloisite 30B in matrix resulted in much higher thermal stability and char yield with respect to modification of novolac resin originated from formation of 3D Si–O–Si network. Also, cured modified resin and its nanocomposites showed much higher thermal stability than cured NR and its nanocomposites. Such nanocomposite materials with high thermal stability have potential applications in advanced fields such electronic, industrial molds, coatings, adhesives, and aerospace composites.

Copper(II) Coordination Complex Constructed from Halogenated Tetradentate Schiff Base Ligand: Synthesis, Crystal Structure, and Hirshfeld Surface Analysis

Copper complex [Cu-3Br-salen]] (3-Br-salen = N,N'-bis(3-bromosalicylidene)ethylene-1,2-diamine) is synthesized as a part of the research work of exploring the relationship between the constitution of Schiff-base ligands and the complex structures. The single-crystal X-ray diffraction analysis indicates that the title compound crystallizes in the monoclinic system, sp. gr. Pbca, Z = 8. IntermolecIular hydrogen bonds and the π···π stacking interactions form 2D networks between which there is only van der Waals interaction. Besides, Hirshfeld surface analysis was used to further study the intermolecular interactions of the complexes.

Morphology, structure, and segmental dynamics in polyazomethine/hybrid carbon nanofillers composites

AbstractThe polyazomethine/hybrid carbon nanofillers composites were fabricated. The nanofilles were comprised of thermally reduced graphene oxide (rGO) and multi‐walled carbon nanotubes (MWCNTs) varying in rGO:MWCNTs ratio; the total nanofillers loading was 1 wt%. The scanning electron miscroscopy images revealed uniform distribution of the hybrid nanofillers and formation of 3D networks between rGO and MWCNTs. Molecular dynamics of the polymer chains in these nanocomposites was investigated with broadband dielectric spectroscopy. The polymer fragility, the dielectric glass transition temperature, and the dielectric relaxation strength of the nanocomposites were evaluated and analyzed depending on the rGO:MWCNTs ratio. The thermal glass transition temperature and the thermal relaxation strength evaluated from the differential scanning calorimetry data were shown to behave in other manner. This behavior was interpreted in terms of a fraction of polymer being immobilized in an interfacial layer around the nanoparticles.

Removal of tetracycline hydrochloride from aqueous solution by three 3D uranyl-organic frameworks

Nitroterephthalic acid (H2ntp), 2,5-dibromoterephthalic acid (H2bdc) and N,N′-donor ligands have been employed to synthesize three uranyl compounds: (H2-tmp)[(UO2)(ntp)2]·H2O (1), (2,2′-Hbpy)[(UO2)2(ntp)2.5]·H2O (2) and [(UO2)(bdc)(4,4′-bpy)0.5] (3) [where 2,2′-bpy = 2,2′-dipyridyl, 4,4′-bpy = 4,4′-dipyridyl, tmp = tetramethylpyrazine]. Single-crystal X-ray crystal structures of compounds 1–3 have been determined. Compounds 1 and 2 consist of dinuclear units, which are linked by ntp2− ligands on the equatorial plane to form 2D network, the layers are further bridged by the carboxylate at the angles of 118.69° (1) and 106.18° (2) in the axial position to form the 3D frameworks. In compound 3, each uranyl center is bridged by four bdc2− ligands to form a 3D framework with the carboxylate at the angle of 73.96° on the equatorial plane, and the 4,4′-bpy further consolidates the crystal structure. Compounds 1–3 have been characterized by IR, powder X-ray diffraction, UV-vis absorption spectroscopy, thermogravimetric analysis and photoluminescence spectroscopy. In addition, the photocatalytic degradation of 1, 3 and the performance for tetracycline hydrochloride adsorption of 2 have been investigated.

Synthesis of RGO/AC/Fe3O4 composite having 3D hierarchically porous morphology for high effective electromagnetic wave absorption

The 3D hierarchically porous reduced graphene oxide/cornstalk activated carbon/Fe3O4 (RGO/AC/Fe3O4) composite was synthesized by a simple mixing process combined with heat treatment process. AC could facilitate the formation of 3D network and the good dispersion of fillers in the composite. The well-constructed 3D hierarchically porous microstructure due to the introduction of AC was beneficial for good synergistic effect and multiple transmission-absorption mechanism. With 5% mass fraction of RGO/AC/Fe3O4 in paraffin wax, the minimum RL value reached −34.78 dB at 11.90 GHz, and the absorption bandwidth (RL < −10 dB) was 5.82 GHz with a thickness of 3.0 mm.

A vesicle-to-sponge transition via the proliferation of membrane-linking pores in ω-3 polyunsaturated fatty acid-containing lipid assemblies

We investigate the nanostructure evolution and the membrane reorganization of diluted lipid dispersions of self-assembled monoolein (MO)/eicosapentaenoic acid (EPA, 20:5) mixtures by synchrotron small-angle X-ray scattering (SAXS) and cryogenic transmission electron microscopy (cryo-TEM) microscopy. The nonlamellar lipid phase containing a ω-3 polyunsaturated fatty acid was fragmented into stable nanoscale objects with the help of PEGylated lipids. The Cryo-TEM imaging revealed the transformation pathway of the vesicular bilayer membranes into sponge nanoparticles (spongosomes) in excess aqueous medium. At ambient temperature, the topological transition occurred through the proliferation of membrane-linking pores (MLP) within the individual lipid nanoparticles. The density of the MLP pores varied starting from the nanoparticle center toward the periphery. The generation of MLP is governed by the amphiphilic composition and leads to formation of 3D networks of aqueous channels inside the nanoparticles, i.e. spongosomes. A higher density of MLP pores was established at increasing fraction of EPA in the mixed lipid membranes. This corresponded to sponge particles of less hydrated internal structure, i.e. with smaller-size aqueous compartments. Synchrotron SAXS patterns characterized the overall structural transition from vesicles to sponge membranes in the studied lipid systems. It can be concluded that the incorporation of a ω-3 polyunsaturated fatty acid at increasing concentration causes swelling inhibition (dehydration) of the host liquid crystalline architectures.

Bionics-Inspired Strong Coupling of Streptococcus-Like NiCo2O4 to Needle-Like MnO2 for Enhanced Electrocatalytic Determination of Glucose

Bionics-inspired streptococcus-like NiCo2O4 coated needle-like MnO2 architecture has been synthesized successfully, denoted as NiCo2O4-MnO2, and the nonenzymatic electrochemical sensor based on NiCo2O4-MnO2 exhibits highly sensitive determination toward glucose. MnO2 nanowires are regarded as effective nucleation sites, which allows uniformly growing of NiCo2O4 as electrocatalytic centers on its surface by a hydrothermal method. The rational combination of streptococcus-like NiCo2O4 and needle-like MnO2 can effectively prevent the aggregation of nanomaterials due to the formation of 3D network, promote the electron transportation, and provide more electrocatalytic sites. The attractive nanostructure and composition were better confirmed by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy, etc. The strong coupling of NiCo2O4-MnO2 inspires the synergistic effect, showing a low detection limit of 0.036 μM (S/N = 3) for glucose in 0.1 M NaOH, a high sensitivity of 2887.57 μAmM−1cm−2 and a wide response range (from 1 to 7100 μM). Moreover, the novel sensor exhibited high stability and good reproducibility. The sensor was highly selective to glucose in the presence of commonly interfering species like dopamine, uric acid, ascorbic acid, sodium chloride, fructose, galactose and mannose, and successfully applied to sensing glucose concentration in human serum samples.

Supramolecular assembled networks in crystal structure built up of copper(II) dipicolinates with pyrazine- and pyridinecarboxamides connected through hydrogen bonds

New copper(II) dipicolinate complexes containing pyrazine- or pyridinecarboxamides, namely {[Cu(pca)(dipic)(H2O)]·H2O} (1), [Cu(nia)(dipic)(H2O)] (2), {[Cu(mnia)(dipic)(H2O)]·2H2O} (3), {[Cu(inia)(dipic)]n·2nCH3OH} (4) {[Cu(hmnia) (dipic)(H2O)]2·2[Cu(hmnia)(dipic)(H2O)2]·4H2O} (5) and [Cu(denia)(dipic)(H2O)] (6) (dipic = dipicolinate, anion derived from pyridine-2,6-dicarboxylic acid, pca = pyrazinecarboxamide, nia = nicotinamide, mnia = N-methylnicotinamide, inia = isonicotinamide, hmnia = N-(hydroxymethyl)nicotinamide and denia = N,N-diethylnicotinamide) were synthesized, structurally characterised by single-crystal X-ray diffraction analysis and their properties were studied using IR, UV–Vis and EPR spectroscopic techniques. The Cu(II) compounds are of square-pyramidal (1–4 and 6) or square-bipyramidal geometry (5), in which copper(II) centres are coordinated by N donor atom of a nicotinamide or its derivatives, one N donor atom and two O donor atoms of dipicolinate anions and the coordination sphere around the Cu(II) atoms is completed by terminal aqua ligands (besides 4). The complex 4 is a polymer, in which are dipicolinate ligands bridging via O atoms of their carboxylate groups neighbouring Cu(II) atoms. The compound 5 is made up of two different types of complex molecules, dinuclear [Cu(hmnia)(dipic)(H2O)]2 and mononuclear [Cu(hmnia)(dipic)(H2O)2], and lattice solvent molecules in the ratio of 1:2:4. Copper(II) atoms in the dinuclear complex molecules of 5 [Cu(hmnia)(dipic)(H2O)]2 are interconnected through carboxamide O donor atoms of bridging N-(hydroxymethyl)nicotinamide ligands. In most cases are complex molecules to each other and solvent molecules linked together via NH⋯O and OH⋯O hydrogen bonds and form 2D or 3D supramolecular networks. The X-band EPR spectra of six copper(II) complexes were recorded at room and low temperature (98 K). The g-factor relation g// > g⊥ > 2.0023 is consistent with the dx2-y2 ground electronic state.

Formation of 3D networks in polylactic acid by adjusting the cross-linking agent content with respect to processing variables: a simple approach

High-performance biodegradable polymers have attracted considerable attention over the years because of their eco-friendly nature. The effects of processing variables on the efficiency of crosslinking, and the rheological and thermal properties of cross-linked polylactic acid (XPLA) have not been comprehensively addressed yet. In this work, XPLA was prepared through solution casting followed by curing in an oven. Enhancements in properties could be quantified in terms of structural changes in 3D structure of XPLA by varying the amount of dicumyl peroxide (DCP) as a cross--linking agent and curing temperature and time. The XPLAs were characterized by differential scanning calorimetry, thermo-gravimetric analysis, swelling, and rheological techniques. The swelling data revealed an increase in gel fraction by 1.32% per 1 °C temperature rise in the range of 125–195 °C. The results were also indicative of an increase in gel faction by 0.32% per minute in the time range of 5–100 min. Maximum variation in gel fraction occurred at 195 °C with high peroxide content. At this temperature, the variation rate of gel content was about 14.99%. With gel formation evolution, especially at 85% completion stage, the melting point was vanished. Rheological measurements showed that the Newtonian plateau disappeared for the cross-linked samples, simultaneously with the onset of shear thinning and zero-shear viscosity, through which the molecular weight obtained by the Mark–Houwink equation shifted to lower frequencies. A mathematical model based on the Charlesby–Pinner equation was developed for predicting the gel content of the XPLA as a function of curing time and peroxide concentration. The Flory–Huggins parameter also changed during the cross-linking process as a function of cross-linking density. This study is focused on adjusting cross-linking density and processing factors, like temperature and time, to achieve an XPLA with desirable properties.

Study the cooperative noncovalent interactions in Lithium-1, 10-Phenanthroline complex, its DFT calculations and Hirschfield surface analysis

ABSTRACTThe new compound [Li(NO3)(phen)]n (phen: 1,10-phenanthroline) has been synthesized and characterized by elemental analysis, and single crystal X-ray diffraction. The Li+ ion is five coordinated occupied distorted TBP (trigonal bipyramidal) geometry. The Li+ ions are bridged by nitrate anions into 1D polymeric chain. The nitrate anions are coordinated to Li+ ions through chelating and bridging bidentate mode of binding. There are cooperative noncovalent interactions like strong or weak H-bonding, weak π···π and C‒H···π interactions are involved to form 2D network. Thermal properties of this complex have been completely described by thermo gravimetric analysis (TGA). Both molecular and crystal structures of this compound were compared and discussed the intermolecular interactions by using Hirshfeld surface analysis and 2D-fingerprint plots. The optimized molecular geometry by DFT calculations agrees closely with obtained from the crystallographic study. Hirshfeld surface analysis of compound (I) indicates that H···H, π···π and C‒H···π contacts can account for 30.9, 15.0 and 7.4% respectively of the total Hirshfeld surface area.

Switching "on" and "off" the adhesion in stimuli-responsive elastomers.

The present work aims at the preparation of dry adhesives with switchable bonding properties by using the reversible nature of the [4πs+4πs] cycloaddition of anthracenes. Photo-responsive hydrogenated carboxylated nitrile butadiene rubber with photo-responsive pendant anthracene groups is prepared by one-pot synthesis. The formation of 3D networks relies on the photodimerization of the anthracene moieties upon UV exposure (λ > 300 nm). Controlled cleavage of the crosslink sites is achieved by either deep UV exposure (λ = 254 nm) or thermal dissociation at 70 °C. The kinetics of the optical and thermal cleavage routes are compared in thin films using UV-vis spectroscopy and their influence on the reversibility of the network is detailed. Going from thin films to free standing samples the modulation of the network structure and thermo-mechanical properties over repeated crosslinking and cleavage cycles are characterized by low-field NMR spectroscopy and dynamic mechanical analysis. The applicability of the stimuli-responsive networks as adhesives with reversible bonding properties is demonstrated. The results evidence that the reversibility of the crosslinking reaction enables a controlled switching "on" and "off" of adhesion properties. The recovery of the adhesion force amounts to 75 and 80% for photo- and thermal dissociation, respectively. Spatial control of adhesion properties is evidenced by adhesion force mapping experiments of photo-patterned films.

Assembly of Coordination Polymers Using Thioether-Functionalized Octasilsesquioxanes: Occurrence of (CuX)n Clusters (X=Br and I) within 3D-POSS Networks.

For the first time, POSS-based coordination polymers (CPs) have been structurally characterized. These CPs were obtained in high yield via self-assembly reactions of thioether-functionalized polysilsesquioxanes with CuI salts under mild conditions. Single crystal analyses revealed the formation of 3D networks incorporating different secondary building units (SBUs) as connection nodes. The nature of the -SAr functionality allows a fine-tuning of the cluster nuclearity, that is, butterfly-shaped Cu2 X2 or closed cubane-type Cu4 I4 cores. As such, the resulting hybrid materials exhibit a combination of high thermal stability arising from the inorganic POSS core along with interesting luminescent properties conferred by the cubane cluster core. Furthermore, the occurrence of channels has been shown crystallographically in the case of the Cu4 I4 cluster containing CP.

Syntheses and structural characterization of Co(II) and Cd(II) coordination polymers with 1,4-bis(imidazolyl)butane ligand

Two new coordination polymers, {[Co(bib)3](PF6)2}n (1) and [Cd (bib) Cl2]n (2), were prepared at room temperature by the reaction of appropriate salts of cobalt (II) and cadmium (II) with the flexible linker ligands 1,4-bis(imidazolyl) butane (bib). The compounds were characterized by elemental analyses, IR spectroscopy and single crystal X-ray diffraction. In the polymeric structure of 1, the Co(II) ion lies on an inversion centre and adopts the CoN6 octahedral geometry, while in the structure of 2, the Cd(II) ions adopt the CdN2Cl4 pseudo-octahedral geometry. In compound 1, six bib ligands are coordinated to one central cobalt (II) to form an open 3D 2-fold interpenetrating framework of the α-polonium (pcu) type topology, while in compound 2 two bib ligands are coordinated to one central cadmium (II) to form 2D network structure.

Dielectric and Magnetic Relaxation Behavior in Fe78Si9B13/Polyaniline Composites at Radio-Frequency Range

In this paper, Fe78Si9B13/polyaniline composites with different Fe78Si9B13 content are prepared through cryomilling and pressure molding. The dielectric and magnetic properties are investigated experimentally in the frequency range from 10 MHz to 1 GHz. Both dielectric and magnetic Debye-like relaxation behavior are observed in this frequency range. With the increase of the FeSiB content, the loss peaks in the permittivity spectrum show a redshift, but a blueshift in the permeability spectrum. The results indicate that the loss peak shift has a close relationship with the conductivity and domain wall displacement. As affected by the interface of polyaniline and Fe78Si9B13 particles, the conductivity of composites decrease with the increase of FeSiB content until the formation of 3D network of FeSiB particles, leading to the redshift of the loss peak in the permittivity spectrum. Meanwhile, the blueshift in the permeability spectrum is mainly caused by the domain wall displacement with high damping factor.

Heterotrimetallic CuII(L)–LnIII–MIII (M = Cr, Fe; Ln = Pr, Nd, Sm, Gd) Complexes Ranging from 0D Clusters to 1D Chains and 2D Networks: Syntheses, Structures, and Magnetism

Four heterotrimetallic complexes, {[Cu(L)Pr(H2O)4][Fe(CN)6]}2·2CH3OH·5H2O (1), {[Cu(L)Nd(H2O)4][Fe(CN)6]}2·CH3OH·6H2O (2), {[Cu(L)Sm (H2O)4][Cr(CN)6]·CH3OH·3H2O}n (3), and {[Cu(L)Gd(H2O)3][Fe(CN)6]·CH3OH·0.5CH3CN·2H2O}n [4; L = N,N′‐ethylenebis(3‐methoxysalicylideneiminato) dianion] were synthesized by a self‐assembly method and characterized structurally and magnetically. The results indicate that 1 and 2 are discrete hexanuclear clusters, whereas 3 and 4 form 1D regular chains and 2D networks, respectively. Interestingly, all of the structures possess the same structural inner core of CuII(L)–LnIII–MIII units, which can produce a variety of different structural forms. Magnetic measurements reveal that weak d–f magnetic coupling and the single‐ion magnetic effect of the LnIII ions both contribute to the final magnetic behavior.

Facile synthesis of three-dimensional interweaved titania nanotape networks as dye-sensitized solar cell photoanode

The three-dimensional (3D) interweaved TiO2 nanotape networks have been synthesized via a facile hydrothermal method. The X-ray powder diffraction pattern indicates that the as-prepared sample is highly crystallized anatase phase. The field emission scanning electron microscopy images indicate that the as-prepared sample is highly porous and robust structure due to the formation of 3D-network among the individual TiO2 nanotape. The photovoltaic device based on the 3D interweaved TiO2 nanotape networks is fabricated and investigated. The improved device performance is obtained due to improved light scattering ability, increased connection at the TiO2/Ti interface, and enhanced amount of dye loading, as compared to the cell based on the TiO2 nanotube.

Two new metal–organic framework structures derived from terephthalate and linear trimetallic zinc building units

Two new zinc-terephthalate MOFs, (H2NEt2)[Zn3(BDC)3(HCO2)]·1.5DEF (1) and Zn4(BDC)3(HCO2)2(DEF)4 (2), based on trinuclear zinc secondary building units have been solvothermally synthesized from the well-studied MOF-5 system Zn–H2BDC–DEF (H2BDC=1,4-benzenedicarboxylic acid or terephthalic acid; DEF=N,N-diethylformamide). It is shown that adding small amounts of formic acid to this system has a great influence on the formation of 3D networks based upon trimetallic zinc building units Zn3(O2CR)6. The structures of 1 and 2 comprise stacked 36 tessellated 2D zinc-terephthalate layers which are linked into 3D frameworks either by bridging formate monoanions (1) or by in situ generated neutral bridging units Zn(HCO2)2(DEF)4 (2). Flowing supercritical-CO2 activation of 1 led to a partially (∼80%) desolvated and probably collapsed structure (1-SC) with a measured BET (Brunauer–Emmett–Teller) surface area of 38m2g−1.