Mole Proportions Research Articles

Preparation of Y<sub>2</sub>O<sub>3</sub> Nano-Phased Powders by Polyacrylamide Gel Method

Y2O3 nano-phase powders were prepared by polyacrylamide gel method. The mechanism of polyacrylamide gel process and its calcinations procedure were analyzed. The high purity yttria powders can be produced by polyacrylamide gel method at the calcination temperature of 850°C, which is about 100°C lower than prepared by precipitation method. The microstructure of yttria powders prepared in different proportion of monomer and network agent was investigated. When the mole proportion of monomer and network agent is 5:1, the average size of grains is less than 20nm. Some grains grow abnormally if the proportion deviate from this value and there are a lot agglomerates. Development of such an inexpensive and easy technique for synthesis of high purity yttria nano-phase powders can be of commercial significance.

Synthesis and characterization of polyesters from 2,3-bis (4′-hydroxy phenyl) quinoxaline and 2,3-bis (2′-hydroxynaphthalene-6′-yl) quinoxaline

Abstract Two bisphenols containing pendant, quinoxaline moiety; 2,3-bis (4′-hydroxy phenyl) quinoxaline (BHPQ) and 2,3-bis (2′-hydroxynaphthalene-6′-yl) quinoxaline (BHNQ) were synthesized and characterized by FT-IR, 1 H, 13 C NMR and mass spectrometry. Aromatic polyesters and copolyesters were prepared by interfacial polymerization from BHPQ or BHNQ and isophthaloyl chloride or terephthaloyl chloride or a mixture of different mole proportions of (IPC + TPC). These polyesters and copolyesters were characterized by spectroscopic technique, viscosity measurement, solubility, thermal stability, DSC and XRD. Polymers had moderate to high molecular weights as evidenced by the inherent viscosities in the range 0.35–0.78 dL/g for BHPQ series and 0.27–0.52 dL/g for BHNQ series. BHPQ polyesters and copolyesters dissolved in m-cresol, NMP and conc. H 2 SO 4 whereas, BHNQ polyesters and copolyesters were readily soluble in NMP, DMAc, (TCE + phenol) and partly soluble in solvent like CHCl 3 , pyridine, etc. Wide angle X-ray diffraction (WAXD) results showed that introduction of quinoxaline moiety into polymer chain and aromatic phenyl/rigid naphthyl structures lead to crystalinity. Differentional scanning calorimetry of BHNQ polyesters showed the glass transition temperatures in the range of 131–151 °C. BHPQ polyesters did not show any weight loss below 330 °C and retained 27–55% weight at 900 °C when investigated by TGA under nitrogen atmosphere demonstrating good thermal stability BHNQ derived polyesters showed initial decomposition temperatures in range 211–234 °C. The structure–property relationships for the mentioned polyesters are analyzed, as these polyesters are of interest as materials for electronics, microelectronics and membrane separation.

Syntheses, Structures and Luminescent Properties of Metal Halide Complexes Containing 2,3‐Diphenylquinoxaline

AbstractThe reaction of CuI with 2,3‐diphenylquinoxaline (L) in 1:1 mole proportion in CH3CN/THF afforded the dinuclear complex [CuI(L)]2, 1, whereas the reactions of MX2 (M = Cu; Hg) with L in 1:2 mole proportion in CH3OH gave the mononuclear complexes CuX2(L)2 (X = Cl, 2; Br, 3) and HgX2(L)2 (X = Cl, 4; Br, 5). Formulations of all the complexes were determined on the basis of X‐ray crystallography, elemental, IR‐ and emission spectroscopy. X‐ray examination revealed that complex 1 forms the μ,μ‐iodobridged dimer with distorted trigonal planar geometry through coordination of L ligand by one nitrogen atom to the Cu(I) center. The metal centers of complexes 2 and 3 form distorted square planar geometry while those of complexes 4 and 5 form linear geometry. The molecules of these complexes are interlinked through C‐H—π and/or π‐π stacking and anion—π interactions that form the packed structure. All the complexes exhibit emissions which may be tentatively assigned as intraligand (IL) π r̊ π* transitions.

Synthesis and characterization of novel aromatic–aliphatic polyamides from bis-[(4-aminobenzyl)-4-benzamide] ether

Abstract A novel aromatic diamine monomer containing preformed aromatic–aliphatic amide and ether linkage, bis-[(4-aminobenzyl)-4-benzamide] ether (BABE) was prepared from 2-phenylacetonitrile. BABE was characterized by FT-IR, 1H NMR, 13C NMR and mass spectrometry. Five new aromatic polyamides were prepared by low temperature solution polymerization from BABE and different mole proportions of isophthaloyl chloride (IPC) or terephthaloyl chloride (TPC). The resulting polymers were characterized by means of FT-IR, inherent viscosity [ηinh], solubility, differential scanning calorimetry [DSC], thermogravimetric analysis [TGA] and X-ray diffraction [XRD]. Polyamides were obtained in good yields and had moderate to high molecular weights as indicated by inherent viscosities in the range 0.63–1.35 dL/g in (DMAc + 4% LiCl). XRD results showed the partly crystalline nature of polymers and these polymers dissolved in aprotic polar solvents containing LiCl. The solubility of copolyamides improved due to random placement of constituent IPC and TPC during polymerization. DSC analysis of these polyamides showed glass transition temperatures in the range of 197–204 °C, and they showed no weight loss below 336 °C when analyzed by TG. These polyamides have potential applications as engineering materials.

Synthesis and thermal properties of soluble silicon containing phenylated aromatic–aliphatic polyamides

Aromatic polyamides find many applications in diverse and critical areas due to their high thermal stability coupled with high mechanical properties. However most of such aramides are difficult to fabricate because of their limited solubility and high melting temperature. Improvements in processability have been reported by incorporating bulky pendant groups and aliphatic spacer groups. Similarly to improve the solubility of polymers approaches of incorporating silicon in main polymer chain and co-polymerization techniques were useful. We report the synthesis and characterization of a series of phenylated silicon containing aromatic–aliphatic polyamides from a mixture of 2, 5-bis (4-carboxy methylene phenyl)-3, 4-diphenyl thiophene (CMPDT) and bis-(4-carboxy phenyl) dimethyl silane (BCPDS) in various mole proportions, with commercial aromatic diamine. Thus a series of novel co-polyamides having pendant phenyl groups, methylene spacer and silicon moiety was prepared by judicious combination of (CMPDT); BCPDS and aromatic diamine; bis-(4-aminophenyl) ether (ODA), by direct polycondensation using Yamazaki’s phosphorylation method. These high molecular mass polyamides were obtained in high (89–98%) yields and had viscosities in the range of 0.23–0.57 dL/g in DMAc. Polyamides showed improved solubility in polar aprotic solvents, like NMP, DMAc, DMSO and DMF; had high thermal stability; with no mass loss below 335 °C.

Synthesis and characterization of poly(ether ketone ether ketone ketone)/poly(ether ether ketone ketone) copolymers containing naphthalene and pendant cyano groups

Abstract2,6‐Bis(β‐naphthoxy)benzonitrile (BNOBN) was synthesized by reaction of β‐naphthol with 2,6‐difluorobenzonitrile in N‐methyl‐2‐pyrrolidone (NMP) in the presence of KOH and K2CO3. Poly(ether ketone ether ketone ketone)(PEKEKK) /poly(ether ether ketone ketone) (PEEKK) copolymers containing naphthalene and pendant cyano groups were obtained by electrophilic Friedel‐Crafts polycondensation of terephthaloyl chloride (TPC) with varying mole proportions of 4,4′‐diphenoxybenzophenone (DPOBP) and 2,6‐bis(β‐naphthoxy)benzonitrile (BNOBN) using 1,2‐dichloroethane (DCE) as solvent and NMP as Lewis base in the presence of anhydrous AlCl3. The resulting polymers were characterized by various analytical techniques, such as FTIR, DSC, TG, and WAXD. The results indicated that the crystallinity and melting temperature of the polymers decreased with increase in concentration of the BNOBN units in the polymer, the glass transition temperature of the polymers increased with increase in concentration of the BNOBN units in the polymer. Thermogravimetric studies showed that all the polymers were stable up to 536°C in N2 atmosphere. The copolymers have good resistance to acidity, alkali, and organic solvents. Because of the melting temperature (Tm) depression with increase in the BNOBN content in the reaction system, the processability of the resultant coplymers could be effectively improved. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and Properties of Copolymers of Poly(ether ketone ketone) and Poly(ether ether ketone ketone) Containing Naphthalene Moieties and Pendant Cyano Groups

A new monomer containing naphthalene, 2,6-bis( β -naphthoxy)benzonitrile (BNOBN) was synthesized by reaction of β -naphthol with 2,6-difluorobenzonitrile in N-methyl-2-pyrrolidone (NMP) in the presence of KOH and K 2CO3. Novel copolymers of poly(ether ketone ketone) and poly(ether ether ketone ketone) containing naphthalene moieties and pendant cyano groups were prepared by electrophilic Friedel—Crafts solution copolycondensation of terephthaloyl chloride (TPC) with varying mole proportions of diphenyl ether and 2,6-bis( β -naphthoxy)benzonitrile (BNOBN) using 1,2-dichloroethane as solvent and NMP as Lewis base in the presence of anhydrous AlCl3. The crystallinity and melting temperatures of the polymers were found to decrease as the concentration of BNOBN in the polymer increased, whereas the glass transition temperatures of the polymers increased as the concentration of BNOBN in the polymer increased. The copolymers with 20—25 mol% BNOBN had high Tg values of 182—184 ° C; moderate Tm values of 324—335 °C; tensile strengths of 101.8—103.2 MPa, Young’s moduli of 3.14—3.23 GPa, and elongations at break of 15—18%. The copolymers exhibited outstanding thermal stability and good resistance to organic solvents, acidity and alkali.

Quantitative P–T–X constraints on orthopyroxene‐bearing high‐pressure granulites in felsic–metapelitic rocks: evidence from the Huangtuling granulite, Dabieshan Orogen

AbstractHigh‐pressure granulites are generally characterized by the absence of orthopyroxene. However, orthopyroxene is reported in a few high‐pressure, felsic–metapelitic granulites, such as the Huangtuling felsic high‐pressure granulite in the North Dabie metamorphic core complex in east‐central China, which rarely preserves the high‐pressure granulite facies assemblage of garnet + orthopyroxene + biotite + plagioclase + K‐feldspar + quartz. To investigate the effects of bulk‐rock composition on the stability of orthopyroxene‐bearing, high‐pressure granulite facies assemblages in the NCKFMASHTO (Na2O–CaO–K2O–FeO–MgO–Al2O3–SiO2–H2O–TiO2–Fe2O3) system, a series of P–T–X pseudosections based on the melt‐reintegrated composition of the Huangtuling felsic high‐pressure granulite were constructed. Calculations demonstrate that the orthopyroxene‐bearing, high‐pressure granulite facies assemblages are restricted to low XAl [Al2O3/(Na2O + CaO + K2O + FeO + MgO + Al2O3) < 0.35, mole proportion] or high XMg [MgO/(MgO + FeO) > 0.85] felsic–metapelitic rock types. This study also reveals that the XAl values in the residual felsic–metapelitic, high‐pressure granulites could be significantly reduced by a high proportion of melt loss. We suggest that orthopyroxene‐bearing, high‐pressure granulites occur in residual overthickened crustal basement under continental subduction–collision zones and arc–continent collision belts.

Synthesis and properties of poly(aryl ether ketone ketone)/poly(aryl ether ether ketone ketone) copolymers with pendant cyano groups

2,6-Diphenoxybenzonitrile (DPOBN) was synthesized by reaction of phenol with 2,6-difluorobenzonitrile in N-methyl-2-pyrrolidone in the presence of KOH and K2CO3. Poly(aryl ether ketone ketone)/poly(aryl ether ether ketone ketone) copolymers with pendant cyano groups were prepared by the Friedel–Crafts electrophilic substitution reaction of terephthaloyl chloride with varying mole proportions of diphenyl ether and DPOBN using 1,2-dichloroethane as solvent and N-methyl-2-pyrrolidone as Lewis base in the presence of anhydrous AlCl3. The resulting polymers were characterized by various analytical techniques, such as FT-IR, differential scanning calorimeter, thermal gravimetric analysis, and wide-angle X-ray diffraction. The crystallinity and melting temperature of the polymers were found to decrease with increase in concentration of the DPOBN units in the polymer. Thermogravimetric studies showed that all the polymers were stable up to 514°C in N2 atmosphere. The glass transition temperature was found to increase with increase in concentration of the DPOBN units in the polymer when the molar ratios of DPOBN to DPE ranged from 10/90 to 30/70. The copolymers containing 30–40 mol % of the DPOBN units exhibit excellent thermostability at (350 ± 10)°C and have good resistance to acidity, alkali, and organic solvents. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 3601–3606, 2007

Nafion-H catalyzed cyclocondensation reaction for the synthesis of octahydroquinazolinone derivatives

A facile and environmentally friendly Nafion-H catalyzed multicomponent reaction for synthesis of octahydroquinazolinone derivatives is described. In order to improve the yield and selectivity, the effects of the mole proportion of reactants (cyclic β-diketones, urea and aldehydes) and solvents were investigated. The ability to reuse the catalyst, high yields and easy purification are important features of this process. Interestingly, under similar conditions, the use of nicotinaldehyde and isonicotinaldehyde as the aldehyde component of the reaction gives unexpected products that are distinct from Biginelli products. All of the products were characterized by 1H NMR, 13C NMR, EI-MS and IR, and the structure of one Biglnelli product ( 4k) was determined by single-crystal X-ray diffraction.

Self-assembly Molecular Complex by 3,6-Di(pyridin-4-yl)-1,2,4,5-tetrazine with Trimesic Acid through H-Bonding

The reaction of 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine (4-PTA) with trimesic acid (TMA) in methanol solution in a 1.5:1 mole proportion affords molecular complex 1 . The structure was confirmed by single crystal X-ray diffraction study. The compound crystallizes in the triclinic space group P-1 with a = 9.7625(11), b = 11.7298(13), c = 13.0734(13), α = 68.849(10)°, β = 72.701(8)°, γ = 83.937(9)° and Z = 2. The crystal structure of 1 shows hydrogen bonding between 4-PTA and TMA, and the presence of an interstitial H2O molecule in the crystal. The zigzag 1-dimensional framework was constructed by the intermolecular hydrogen bond containing O–H…N, O–H…O and C–H…O interactions. The π–π interactions are the non-covalent forces operating between the pyridine ring in 4-PTA and benzene ring in TMA to generate 3-dimensional network.

One-pot synthesis of Biginelli and Hantzsch products catalyzed by non-toxic ionic liquid (BMImSac) and structural determination of two products

In this paper, both 1,4-dihydropyridinones (Hantzsch products) and 3,4-dihydropyrimidinones (Biginelli products) are synthesized in one-pot of aldehydes, β-dicarbonyl compounds and urea, catalyzing by non-toxic room temperature ionic liquid 1- n-butyl-3-methylimidazolium saccharinate (BMImSac). The ionic liquid (BMImSac) is environmentally benign associated with ionic liquid with F −. In order to improve the yield and selectivity, the effects of the mole proportion of reactants and solvents are investigated. Interestingly, by increasing the amount of ethyl acetoacetate or utilizing water as solvent, an unexpected by-product, Hantzsch product which is distinct from Biginelli product, is generated. All Biginelli and Hantzsch products are simultaneously purified and characterized by IR, 1H NMR and 13C NMR, of which one Biginelli product ( 4h) and one Hantzsch product (5b) are structurally determinated by X-ray single crystal diffraction. The crystal data for 4h: triclinic system, P-1 space group, a = 7.515(3) Å, b = 9.011(4) Å, c = 11.218(5) Å, α = 106.288(6)°, β = 104.644(6)°, γ = 100.234(6)°, Z = 2, V = 679.7(5) Å 3, D c = 1.36 g/cm 3, R 1 = 0.0603. The crystal data for 5b: monoclinic system, P2(1)/ c space group, a = 9.765(3) Å, b = 7.391(2) Å, c = 24.795(7) Å, β = 93.669(5)°, Z = 4, V = 1785.7(9) Å 3, D c = 1.292 g/cm 3, R 1 = 0.0440.

Copper(II) azide complexes of 1-alkyl-2-(arylazo)imidazoles: Structure and magnetism

Tetranuclear Cu(II)-azido complexes of the composition [Cu(RaaiR′)(N 3) 2] 4 have been synthesized by reacting 1-alkyl-2-(arylazo)imidazole (RaaiR′), Cu(OAc) 2 · H 2O and NaN 3 in 1:1:2 mole proportion [RaaiR′; R = H ( 3), Me ( 4); R′ = Me ( a), Et ( b)]. The structure of [Cu(HaaiMe)(N 3) 2] 4 ( 3a) has been confirmed by an X-ray diffraction study. The tetranuclear copper core is generated by dimerisation via μ 1,1-N 3 of two dimer units. In each dimer one copper centre is five-coordinated (CuN 5) and the other one is six-coordinated (CuN 6). Variable temperature magnetic measurements of 3a show the occurrence of ferromagnetic ( J 1 = +25.3 cm −1) and antiferromagnetic ( J 2 = −4.7 cm −1) interactions through the double and single end-on azido bridges, respectively. Upon addition of excess ligand, a 2-methoxy ethanol solution of the tetranuclear complex fragmented into a mononuclear copper(II) complex of the formula [Cu(RaaiR′) 2(N 3) 2], and in one case, [Cu(HaaiEt) 2(N 3) 2], the structure was established by X-ray diffraction.

Synthesis and properties of poly ether nitrile sulfone copolymers with pendant methyl groups

AbstractPoly ether nitrile and poly ether nitrile sulfone copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6′‐dichlorobenzonitrile with methyl hydroquinone and with varying mole proportions of methyl hydroquinone and 4,4′dihydroxydiphenylsulfone using N‐methyl pyrrolidone as solvent in the presence of anhydrous K2CO3. The polymers were characterized by different physicochemical techniques. Copolymer composition was determined using FTIR technique. Thermogravimetric data reveals that all the polymers were stable up to 420°C with a char yield above 40% at 900°C in N2 atmosphere. The glass transition temperature was found to increase and the activation energy and inherent viscosities were found to decrease with increase in concentration of the 4,4′‐dihydroxydiphenylsulfone units in the polymer. Trimerization reactions are found to be favorable with increase in concentration of methyl hydroquinone units in the polymer. Crystallinity of the polymer was also studied using wide angle X‐ray diffraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1303–1309, 2006

Increasing Surface Charge Density Induces Interdigitation in Vesicles of Cationic Amphiphile and Phosphatidylcholine

Binary vesicles of cationic lipid dihexadecyldimethylammoniumbromide (DHAB) and 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were examined by differential scanning calorimetry, fluorescence spectroscopy, and Fourier transform infrared spectroscopy. DHAB/DMPC vesicles demonstrate a complex dependence of the main-transition temperature (T(m)) on their mole proportion of DHAB, with a maximum of 42 degrees C at X(DHAB) = 0.4. An increase of T(m) at X(DHAB) < 0.4 is explained by reorientation of P(-)-N(+) dipoles of the phosphocholine headgroup, resulting in tighter packing of the acyl chains, which increases the thermal energy required for trans --> gauche isomerization. At X(DHAB) > 0.4, Coulombic repulsion between the cationic DHAB headgroups expands the bilayer evident as a decrease in T(m) until a plateau of approximately 28 degrees C at 0.7 < or = X(DHAB) > or = 0.9 is reached, followed by an increment of T(m) to approximately 30 degrees C at X(DHAB) > 0.9. The quenching of DPH-PC fluorescence emission and the decrease in the ratio of peak height intensities of symmetric and antisymmetric -CH(2)- stretching modes suggest an interdigitated phase to form at X(DHAB) > 0.6. Interdigitation allows the membrane to accommodate the augmented Coulombic repulsion between DHAB headgroups because of increasing cationic surface charge density while simultaneously causing tighter packing of the acyl chains evident first as a plateau at 0.7 < or = X(DHAB) > or = 0.9 and subsequently as an increase in T(m) at X(DHAB) > 0.9. Screening of the membrane charges by NaCl abolishes the quenching of DPH emission and decreases T(m), thus revealing electrostatic repulsion as the driving force for interdigitation.

Manganese(II) complexes of pyridyl-azo-imidazoles. Single crystal X-ray structures of 3′-PyaiH and [Mn(3′- PyaiEt) 4](ClO 4) 2 (3′-PyaiH = 2-(3′-pyridylazo)imidazole; 3′-PyaiEt = 1-ethyl-2-(3′-pyridylazo)imidazole)

Pyridine and imidazole are connected by an azo group ( N N ) to synthesize 2-[(3′-pyridyl)azo]imidazole (3′-PyaiH) and this has been confirmed by X-ray structure determination. The N(1)-alkylation gives 1-alkyl-2-[(3′-pyridyl)azo]imidazole (3′-PyaiR′) (R′ = Me ( 2a), Et ( 2b), Bz ( 2c)). The reaction between Mn(ClO 4) 2 · 6H 2O and 3′-PyaiR′ in methanol has synthesized [Mn(3′-PyaiR′) 4](ClO 4) 2 ( 3). The structure has been confirmed by single crystal X-ray diffraction study in one case, in addition to other spectral characterization. The structure reveals a tetrahedral orientation of four ligands coordinating through imidazole-N only. Cyclic voltammetry exhibits a Mn(III)/Mn(II) couple at >1.1 V along with azo reductions. However, the reaction of MnCl 2 · 4H 2O + 3′-PyaiR′ in the presence of NaN 3 or NH 4CNS (1:2:2 mole proportion) has synthesized Mn(3′-PyaiR′) 2(X) 2 (X = N 3 ( 4), NCS ( 5)).

Synthesis and properties of poly(ether nitrile sulfone) copolymers with pendant methyl groups

Poly(ether nitrile) and poly(ether nitrile sulfone) copolymers with pendant methyl groups were prepared by the nucleophilic substitution reaction of 2,6′-dichlorobenzonitrile with methyl hydroquinone and with varying mole proportions of methyl hydroquinone and 4,4′-dihydroxydiphenylsulfone using N-methyl pyrrolidone as a solvent in the presence of anhydrous K2CO3. The polymers were characterized by different physicochemical techniques. Copolymer composition was determined using the FTIR technique. Thermogravimetric data revealed that all polymers were stable up to 420°C with a char yield above 40% at 900°C in a nitrogen atmosphere. The glass-transition temperature increased and the activation energy and inherent viscosities decreased with an increase in the concentration of the 4,4′-dihydroxydiphenylsulfone units in the polymer. Trimerization reactions were favorable with an increase in the concentration of methyl hydroquinone units in the polymer. The crystallinity of the polymer was also studied using wide-angle X-ray diffraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1987–1994, 2005

Iron(II) and nickel(II)-thiocyanato complexes of 1-alkyl-2-(arylazo)imidazole: single crystal X-ray structure of [Fe(MeaaiEt) 2(NCS) 2] (MeaaiEt = 1-ethyl-2( p-tolylazo)imidazole) and [Ni(MeaaiMe)(NCS) 2(H 2O) 2] · 2DMF (MeaaiMe = 1-methyl-2( p-tolylazo)imidazole)

The reaction of green vitriol (FeSO 4,7H 2O) with 1-alkyl-2-(arylazo)imidazoles [RaaiR′ where R = H ( a), Me ( b); R′ = Me ( 1/ 3/ 5), Et ( 2/ 4/ 6)] and NH 4SCN in 1:2:2 mole proportion affords mononuclear bis-chelated [Fe(RaaiR′) 2(SCN) 2] ( 3, 4) complexes. Reaction of NiSO 4 · 6H 2O with 1-alkyl-2(arylazo)imidazole and ammonium thiocyanate (1:2:2 molar ratio) in methanol solution forms mononuclear monochelated thiocyanato complexes of the type [Ni(RaaiR′)(H 2O) 2(SCN) 2] · 2H 2O ( 5, 6). Slow diffusion of DMF solution of [Ni(MeaaiMe)(H 2O) 2(NCS) 2] in methanol has isolated the X-ray quality crystals. All the complexes are characterized by elemental, UV–Vis, IR, thermal and magnetic studies. In both cases, the distorted octahedral structure was confirmed by single crystal X-ray diffraction study of [Fe(MeaaiEt) 2(NCS) 2] ( 4b) and [Ni(MeaaiMe)(H 2O) 2(NCS) 2] · 2DMF ( 7). Variable temperature susceptibility measurements of [Fe(MeaaiEt) 2(NCS) 2] ( 4b) do not exhibit spin crossover property, which may be due to high structural distortion.

Synthesis and properties of poly(aryl ether ether ketone) copolymers with pendant methyl groups

Polyether ether ketone and polyether ether ketone copolymers were prepared by the nucleophilic substitution reaction of 4,4′-difluorobenzophenone with hydroquinone and with varying mole proportions of hydroquinone and methyl hydroquinone using sulfolane solvent in the presence of anhydrous K 2CO 3. The polymers were characterised by different physico-chemical techniques. The crystallinity of the polymers was found to decrease with increase in concentration of the methyl hydroquinone units in the polymer. Thermogravimetric studies showed that all the polymers were stable upto 430 °C with a char yield above 49% at 900 °C in N 2 atmosphere. The glass transition temperature was found to increase and the crystalline melting temperature and activation energy were found to decrease with increase in concentration of the methyl hydroquinone units in the polymer.

Synthesis and Properties of Polyarylene ether Nitrile Copolymers

Polyether nitrite and its copolymers were synthesized by nucleophilic substitution reaction of 2,6-dichlorobenzonitrile with resorcinol and with varying mole proportions of resorcinol and hydroquinone. The polymers were characterized by different physico-chemical techniques. Thermogravimetric studies showed that all the polymers were stable up to 400°C with a char yield of above 48% at 900°C in N 2 atmosphere. The glass transition temperature was found to increase with increase in concentration of hydroquinone units in the polymer; however no trend was observed in their crystalline melt temperatures. Copolymer composition was determined using FT-IR technique. Crystallinity of the polymers was also studied using wide angle X-ray diffraction.