Liquid phase synthesis of aromatic poly(azomethine)s,their physicochemical properties,and measurement of ex situ electrical conductivity of pelletized powdered samples

Aromatic bis-aldehydes have been used as building blocks in the synthesis of polyazomethines (a class of conjugated Schiff bases) and their physicochemical properties have been studied. Six dialdehydes have been synthesized, 3a-3f, via etherification reaction between aromatic diols (2a-2f) and 4-fluorobenzaldehyde (1) (see Scheme 1), and then polymerized with 1,4-phenylenediamine (4a) and 4,4′-oxydianiline (4b) (see Scheme 2). The chemical structures of the bis-aldehydes were elucidated by FTIR, ¹H NMR and ¹³C NMR spectroscopic studies, elemental analysis and single crystal whereas the polymers were studied by FTIR and NMR spectroscopy. Their physicochemical properties were examined by their inherent viscosity, organosolubility, differential scanning calorimetry, X-ray powder diffraction, thermogravimetric analysis, solvatochromism, and photoluminescence. We report the electrical conductivity of each polymer measured by the four probe method. The results indicate that the electrical conductivity of polymers lies in range 0.019–0.051 mScm^?1 which is reasonably higher than any reported value.     

Synthesis of some new polyers and copolymers from 2,2-bis (4-chlorophenyl) 1, 1, 1-trichloro ethane (DDT)

DDT (I) was polycondensed with 2,2-bis(4-hydroxy phenyl)- propane (bisphenol-A) to form polyether. The following monomers were synthesised from DDT: 2,2-bis(4-chloro-phenyl)1, 1-dichloroethylene(II), 2,2-bis(3-nitro-4-chlorophenyl)ethane (III) and 2,2-bis (3-nitro-4-chloro-phenylethylene (IV) and polycondensed with bisphenol-A. They were also copolymerised with bis(4-chlorophenyl)sulphone and bisphenol-A in several molar ratios. The polymers and copolymers were characterised by various techniques. The results obtained show that the DDT has a low reactivity, but nitration and dehydrochlorin-ation increases its reactivity to a significant extent.     

Self-Recognition of 3D Porous Frameworks: Fourfold Diamondoid or Threefold Cuboidal Interpenetrating Nets Formed by Varying Pillar Motifs

Compound [Ni(2,6-ndc)(bpe)(H₂O)] _n (1) was prepared by the hydrothermal reaction of 2,6-naphthalenedicarboxylic acid (2,6-H₂ndc) and trans-1,2-bis(4-pyridyl)ethylene (bpe) with Ni(NO₃)₂·6H₂O under alkaline (NaOH) conditions. Treatment of 2,6-H₂ndc, 4,4′-bipyridine (4,4′-bpy) with M(NO₃)₂·6H₂O (M = Ni or Co) under similar conditions afforded compounds [Ni₂(2,6-ndc)₂(4,4′-bpy)] _n (2) and [Co₂(2,6-ndc)₂(4,4′-bpy)] _n (3), respectively. A single-crystal X-ray diffraction study revealed that compound 1 adopts a 3D fourfold interpenetrating diamondoid network stabilized by inter-net OH···O hydrogen bonds. The anionic 2,6-ndc ligand presents two different bonding characteristics, bis(monodentate) and bis(chelating bidentate) modes. A solid-state structural analysis revealed that compounds 2 and 3 are isomorphous and isostructural. Both present a 3D threefold interpenetrating cuboidal framework, consisting of a 2D (4,4)-net of interconnected [M ₂(O₂C)₄] (M = Ni, Co) paddle-wheel dinuclear units, and pillared by 4,4′-bpy ligands. The degree of interpenetration of these compounds could be adjusted successfully by varying only the organic pillar motifs.     

Synthesis of New Polyimides from Ru (II) Complex of 2,6-bis [1-(p-dimethylaminophenylimino) Ethyl] Pyridine

Pyridine-based tridentate ligand containing pendant NMe₂ unit was used to prepare novel polyimides via one-stage solution polycondensation due to their stability under a variety of oxidative and reductive conditions. Ru (II) complex of the pydim ligand was synthesized starting from [RuCl₂ (p-cymene)]₂ and 2,6-bis [1-(p-dimethylaminophenylimino) ethyl] pyridine. A series of stable polyimides were synthesized from Ru (II) complex of 2,6-bis [1-(p-dimethylaminophenylimino) ethyl] pyridine (2) and various aromatic dianhyrides had inherent viscosities ranging from 1.31 to 1.55 dL/g and were soluble in polar solvents. The glass transition temperatures were 245–308°C, and the 10% weight loss temperatures were above 482–548°C.     

Development of epoxy-cyanate ester-clay nanocomposites offering enhanced thermally stability

The preparation and characterization of blends of a series of dicyanate monomers such as 2,2′-bis(4-cyanatophenyl) propane (DCDPP), bis-4-cyanato-biphenyl (DCBP), bis-4-cyanatonaphthalene (DCN), 3,3′-bis(4-cyanatophenyl)sulphide (DCTDP), 3,3′-bis(4-cyanatophenyl)sulphone (DCDPS), and the diglycidyl ether of bisphenol A are reported. These copolymers are combined with a montmorillionite nanoclay and both epoxy-cyanate blends and epoxy-cyanate blends-nanoclay composites are all analyzed for thermal stability, thermal degradation kinetics, flame retardancy, and impact strength. The nanocomposites are further characterized by X-ray diffraction and SEM to determine morphological features, from which structure–property relationships are determined. Dispersion of the nanoclay is of paramount importance, but its inclusion serves to improve char yield and impact strength, when this is achieved. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47754.     

Poly(Amide‐Imide)s Based on Amino‐Terminated Oligoimides

Abstract

An amino‐terminated oligoimide was prepared by the Michael addition reaction of ethylene bis‐maleimide (EBM) and 4,4′‐diamnio diphenyl‐sulfone (DDS) at an EBM:DDS molar ratio of 1:2. The poly(amide‐imide)s (PAI)s were prepared by condensation of this EBMDDS oligoimide with various aliphatic bisesters. The resultant PAIs were characterized by elemental analysis, IR spectral studies, and the number average molecular weight estimated by non‐aqueous conductometric titration and thermogravimetry. The curing reaction of an epoxy resin [a diglycidyl ether of bis‐phenol‐A (DGEBA)] with PAIs was monitored by differential scanning calorimetry (DSC). Glass‐ and carbon‐reinforced laminates of PAI‐epoxy resin were also prepared and characterized.     

Formation of Diruthenium(II) Complexes Containing 2,2′;6′,2′′-Terpyridine Domains Possessing Rotationally Restricted Connectivity: The Influence of Shape-Persistence

The synthesis and characterization of a structurally related series of bis-terpyridine diruthenium(II) complexes are described. Two of the complexes (10 and 11) contained elements of rotational immobility around the central axis due to a mesitylene moiety, while two other complexes (12 and 13) were free-to-rotate about the central tolyl moiety. It was found that the complexes that included the mesitylene moiety in the central region showed a unique splitting pattern of the protons associated with the inner bis-terpyridine, while the complexes that lacked the mesitylene showed no such splitting; there was also no unusual splitting observed for the complexes that contained a peripheral mesitylene group. Molecular modeling calculations indicated the rotational barrier around the central axis of the mesitylene moiety to be substantially greater than the rotational barrier of the tolyl group. The X-ray crystal structure of the rotationally frozen ligand is also described.     

Synthesis and characterization of copolymers with alternating 1,4-bis(5'-acetyl-2'-thienyl)benzene or 1,3-bis(5'-acetyl-2'-thienyl)benzene chromophore and disiloxane units

Summary Activated (Ph₃P)₃RuH₂CO (Ru) catalyzed copolymerization of 1,4-bis(5'-acetyl-2'-thienyl)benzene (I) and 1,3-divinyltetramethyldisiloxane (II) yields alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,4-benzene)-3',3"-bis (thiophenylene)] (III). On the other hand, Ru catalyzed copolymerization of 1,3-bis(5'-acetyl-2'-thienyl)benzene (IV) and II fails. Nevertheless, Ru catalyzed reaction of IV with excess vinylpentamethyldisiloxane (V) yields 1,3-bis(4'-pentamethyldisiloxy-ethyl-5'-acetyl-2'-thienyl)benzene (VI). VI undergoes acid catalyzed siloxane equilibration polymerization to give alt-copoly[3,3,5,5-tetramethyl-4-oxa-3,5-disila-1,7-heptanylene/2',2"-diacetyl-5',5"-(1,3-benzene)-3',3"-bis(thiophenylene)] (VII) and hexamethyldisiloxane. Copolymers III and VII have been characterized. Received: 26 July 1999/Revised version: 12 October 1999/Accepted: 12 October 1999     

Two Novel Bimetallic Cyano-Bridged Coordination Polymers Containing the 2,2′-(Ethylenedioxy)bis (Ethylamine): Syntheses,Structural, Thermal and Magnetic Properties

Two new cyano bridged bimetallic polymeric complexes, [Ni(edbea)Ni(CN)₄]·1/2H₂O (1) and [Cu(μ-edbea)(μ-CN)₂ Ni(CN)₂]·H₂O (2) [edbea = 2,2′-(ethylenedioxy)bis(ethylamine)] have been synthesized by adding metal chloride (M = Ni^II and Cu^II), and edbea into [Ni(CN)₄]²⁻ in water–ethanol solution and then characterized by elemental analysis, infrared (IR) and electron paramagnetic resonance (EPR) (for only complex 2) spectra, variable temperature magnetic measurement, and thermal gravimetric analysis. The X-ray diffraction crystal structure of complex 2 shows a 2D polymeric chain –edbea(N5,O1)–Cu1–N1C1–Ni(CN)2–C4N6–Cu1–(N6,O2) edbea– in which the Cu^II centers are linked by two cyano and one edbea. The powder EPR spectrum of the complex 2 has shown that Cu^II ions are located in rhombically distorted octahedral sites. The magnetic properties of the coordination polymers have been studied in temperature range of 15–300 K. The magnetic behaviors investigation of complexes 1 and 2 indicated the presence of a very weak antiferromagnetic interaction.     

Polyimides from a Novel Monomer 3,6-Bis(dimethylamino)acridine(p-cymene)dichlororuthenium(II) for a Catalytic Application

Tricyclic heteroaraomatic dye-based monomer containing NMe₂ units, 6-bis(dimethylamino)acridine(p-cymene)dichlororuthenium (II), was used to prepare novel polyimides via a one-stage solution polycondensation due to their stability under a variety of oxidative and reductive conditions. The Ru(II) complex monomer was synthesized starting from [RuCl₂(p-cymene)]₂ and 3,6-bis(dimethylamino)acridine. A series of stable polyimides was synthesized from the Ru(II) complex of 3,6-bis(dimethylamino)acridine and various aromatic dianhyrides. The polymers had inherent viscosities ranging from 1.72 to 2.11 dL/g and were soluble in polar solvents. The glass transition temperatures were 192–278 °C, and the 10% weight loss temperatures were above 503–635 °C. Ruthenium-substituted polyimides were tested for catalytic activity in the furan formation reaction of (Z)-3-methylpent-2-en-4-yn-1-ol. The polymeric catalyst was added to (Z)-3-methylpent-2-en-4-yn-l-ol without a solvent and the pure furan was isolated by distillation under reduced pressure. The conversion of the starting, enynol, was determined by gas chromatography (GC).     

A study of the polymerization behaviour of N-(4-phenoxy)-phenylmaleimide using DSC analysis

Summary The thermal cure of a monofunctional maleimide N-(4-phenoxy)-phenylmaleimid (1) was examined using differential scanning calorimetry (DSC). The analogous bis-maleimide bis-(4-maleimidophenyl)ether (2) was also analyzed in the same manner for comparison. Polymerization kinetics derived from scanning DSC measurements showed an order of reaction varying between n=1 and 2 for (1), compared to an order of reaction between n=2 and 3 (by multiple linear regression analysis) for (2). The overall enthalpy of polymerization (H_o) for N-(4-phenoxy)-phenylmaleimide (94kJ/mole) agrees well with that obtained for maleimide itself (89kJ/mole) using conventional calorimetric techniques indicating that polymerization appears complete within the timescale of the experiment. In contrast the analogous BMI displays a markedly lower overall polymerization enthalpy (ca. 66kJ/mole) indicating an apparent conversion of only 37%.     

Synthesis and properties of flourine-containing polyimides

A series of new flourine-containing polyimides have been synthesized from the condensation of 2,2,-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-amino-phenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, or 2,2bis[4-(4-amino-2-trifluoro-methylphenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane with various aromatic dianhydrides. The electric constant at 1 KHz in the flourine-containing polyimides decreases from 3.51 to 2.72 as flourine content increases. The poly(amic acid)s had inherit viscosities of 0.52–1.23 dL/g, depending on the diamines and dianhydrides. Most of the resulting polymers showed an amorphous nature and afforded flexible and tough films. The amount of moisture absorption decreases as flourine content in polyimides increases. The glass transition temperatures of these polyimides were in the range of 287–328°C, and the 10% weight loss temperatures were above 542°C in the nitrogen. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 609–617, 1997     

Complexation of Tolane by Fluorinated Organomercurials—Structures and Luminescence Properties of an Unusual Class of Supramolecular π-Coordination Polymers

The interaction of the Hg(II) derivatives bis(pentafluoro)phenyl mercury (1), (pentafluoro)phenyl mercury chloride (2) and trimeric perfluoro-ortho-phenylene mercury (3) with tolane (diphenylacetylene) in CH₂Cl₂ leads to the formation of [1·tolane], [2 ₂·tolane], and [3·tolane·CH₂Cl₂]. These adducts have been characterized by elemental analysis, X-ray crystallography, and luminescence spectroscopy. In the solid state of these adducts, the tolane molecules interact with the molecules of 1, 2 and 3 via secondary Hg–π interactions and arene–fluoroarene interactions. As a result of an external mercury heavy atom effect, adducts [1·tolane] and [2 ₂·tolane] are phosphorescent at room temperature.     

Ascorbate and phenolic antioxidant interactions in prevention of liposomal oxidation

Efficient prevention of membrane lipid peroxidation by vitamin E (α-tocopherol) may involve its regeneration by vitamin C (ascorbate). Conceivably, the efficacy of antioxidants designed as therapeutic agents could be enhanced if a similar regeneration were favorable; thus, a model membrane system was developed which allowed assessment of interaction of phenolic antioxidants with ascorbate and ascorbyl-6-palmitate. Ascorbate alone (50–200 μM) potentiated oxidation of soybean phosphatidylcholine liposomes by Fe²⁺/histidine-Fe³⁺, an effect which was temporally related to reduction of Fe³⁺ generated during oxidation. Addition of 200 μM ascorbate to α-tocopherol-containing liposomes (0.1 mol%) resulted in marked, synergistic protection. Accordingly, in the presence but not absence of ascorbate, α-tocopherol levels were maintained relatively constant during Fe²⁺/histidine-Fe³⁺ exposure. Probucol (4,4′-[(1-methylethylidine)bis(thio)]bis[2,6-bis(1,1-dimethylethyl)]phenol), and antioxidant which prevents oxidation of low density lipoproteins, and its analogues MDL 27,968 (4,4′-[(1-methylethylidene)bis(thio)]-bis[2,6-dimethyl]phenol) and MDL 28,881 (2,6-bis(1,1-dimethylethyl)-4-[(3,7,11-trimethyldodecyl)thio]phenol) prevented oxidation but exhibited no synergy with ascorbate. Ascorbyl-6-palmitate itself was an effective antioxidant but did not interact synergistically with any of the phenolic antioxidants. Differential scanning calorimetry revealed significant differences among the antioxidants in their effect on the liquid-crystalline phase transition of dipalmitoyl phosphatidylcholine (DPPC) liposomes. Both α-tocopherol and MDL 27,968 significantly reduced the phase transition temperature and the enthalpy of the transition. MDL 28,881 had no effect while probucol was intermediate. The potential for ascorbate or its analogues to interact with phenolic antioxidants to provide a more effective antioxidant system appears to be dictated by structural features and by the location of the antioxidants in the membrane.     

Synthesis, Crystal Structure and Magnetic Properties of a Nickel(II) Coordination Polymer Based the V-Shaped Ligands

Abstract  

A new nickel(II) coordination polymer, Ni₂(DBA)₂(BIDPE)₂(H₂O) (1) (H₂DBA = 4,4′-methylenedibenzoic acid and BIDPE = 4,4′-bis(imidazole-l-yl)diphenyl ether), has been prepared by hydrothermal synthesis and structurally characterized by IR, elemental analysis, TGA and single crystal X-ray diffraction. Complex 1 features a one-dimensional chain structure based on triply bridged binuclear units, which is further interlinked into a higher-dimensional supramolecular framework by intermolecular weak interactions. Variable-temperature magnetic data shows weak antiferromagnetic behavior in 1.     

Hydrothermal Synthesis of Cd(II), Mn(II) and Ni(II) Coordination Polymers Derived from Benzopenone-2,4′-carboxylate and N-door Ligands

Three new coordination polymers [Cd(L)(4,4′-bipy)_0.5]_n (1), {[Mn(L)(bpp)]·H₂O}_n (2) and [Ni(L)(2,2′-bipy)(H₂O)₂]_n(3) [H₂L = Benzopenone-2,4′-dicarboxylic acid, 4,4′-bipy = 4,4′-bipy ridine, bpp = 1,3-di(4-pyridyl) propane and 2,2′-bipy = 2,2′-bipyridine] have been synthesized and structurally characterized by elemental analysis, IR and X-ray diffraction. Single-crystal X-ray analyses revealed that the H₂L ligand acts as a bridge, exhibiting three coordination modes to link metal ion: bidentate chelating, bis-monodentate, monodentate. Compound 1 has 3-connected metal–organic framework with the (6³) topology notation; Compounds 2 and 3 are one-dimensional chain structures. The luminescent properties for compound 1 was investigated.     

Effects of Different Silane Coupling Agent Monomers on Flexural Strength of an Experimental Filled Resin Composite

The hydrolytic stability of various silane combinations and their effects on biomechanical properties and water sorption of an experimental dental composite made of bis-GMA and TEGDMA and silane-treated fillers were evaluated. Four silane coupling agents and their blends with a cross-linker silane were used as coupling agents for the 0.7-μm BaSiO₃ fillers. The silanization was carried out in toluene containing 1% (v/v) of one of the four following organofunctional silane coupling agents: 3-acryloxypropyltrimethoxysilane, 3methacryloxypropyltrimethoxysilane, 3-styrylethyltrimethoxysilane and 3-isocyanatopropyltriethoxysilane. Blends of these functional silanes with 1% (v/v) of a cross-linker silane, 1,2- bis -(triethoxysilyl)ethane were also used for silanization. Composites were prepared by mixing 5.00 g Ba-glass filler with 2.00 g of a resin mixture consisting of bis-GMA (58.8 wt%) and TEGDMA (39.2 wt%) in a high-speed mixer. Threepoint bending test specimens (2.0 mm × 2.0 mm × 25.0 mm) were fabricated (n= 8) in a mould and photo-polymerized. The degree of conversion was measured with FT-IR. Biomechanical testing was carried out according to the ISO 10477 standard. Specimens were tested (flexural strength) after 30 days of water storage (37° C, distilled water). Water sorption and solubility (in wt%) were also measured on 1, 2, 3, 5, 7, 14, 21 and 30 days in water storage. Statistical analysis with ANOVA showed that the highest flexural strength was obtained when 3-acryloxypropyltrimethoxysilane + 1,2- bis -(triethoxysilyl)ethane (100.5 MPa; SD, 25.7 MPa) was used in the silanization step, and the lowest was obtained when 3isocyanatopropyltriethoxysilane + 1,2- bis-(triethoxysilyl)ethane (28.9 MPa; SD, 8.8 MPa) was used. The three-point bending strength was significantly affected by the functionality of the main silane tested (p< 0.05), but not by the addition of the cross-linker silane ( p> 0.05). The composite that had been silanized with 3-isocyanatopropyltriethoxysilane had the greatest amount of water uptake (1.75%), and the composite silanized with 3-methacryloxypropyltrimethoxysilane + 1,2- bis-(triethoxysilyl)ethane had the least (1.08%). In conclusion, selection of the functional silane monomer can be a significant factor in developing filled resin composites in dentistry.     

The synthesis and characterization of a mesomorphic brush type polycarbosilane: poly[1,1-bis(4′-biphenyl)silabutane]

Summary Poly[1,1-bis(4-biphenyl)silabutane] (II) has been prepared by the anionic ring opening polymerization of 1,1-bis(4-biphenyl)silacyclobutane. II shows mesomorphic behavior by DSC. The¹³C NMR T₁ relaxation times have been measured. These are found to be smaller than those of poly(1,1-dimethylsilabutane)by an order of magnitude. This may result from interaction of the highly rigid biphenyl side chain moieties. The thermal stability of II is higher than that for other 1,1-disubstituted polysilabutanes.     

Experimental Novel Silane System in Adhesion Promotion between Dental Resin and Pretreated Titanium. Part II: Effect of Long-Term Water Storage

In this study we have assessed the effect of long-term water storage at 37^oC on silane-aided adhesion promotion. Five experimental silane blends were evaluated as adhesion-promoters. First, five functional organosilane monomers (silicon esters), 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, tetrakis-(2-methacryloxyethoxy)silane and bis-[3-(triethoxysilyl)propyl]tetrasulfide, were diluted to 1% (v/v) in 95% ethanol and blended with a non-functional cross-linking silane, bis-1,2-(triethoxysilyl)ethane (1%). A commercially available pre-activated silane product was used as the control. After activation by hydrolysis, each primer blend was applied to silica-coated Ti coupons. Stubs of experimental bis-phenol-A-diglycidyldimethacrylate (bis-GMA)-based resin were bonded by photo-polymerization onto the pretreated Ti coupons. Half of the specimens were stored in deionized water for 6 months and half for 12 months. The primer containing 3-acryloxypropyltrimethoxysilane and bis-1,2-(triethoxysilyl)ethane produced significantly higher shear bond strengths than the control silane and other experimental silane primers after both periods of storage.