Synthesis,characterization, and kinetic of thermal degradation of oligo‐2‐[(4‐bromophenylimino)methyl]phenol and oligomer‐metal complexes

Oligo‐2‐[(4‐bromophenylimino)methyl]phenol (OBPIMP) was synthesized from the oxidative polycondensation reaction of 2‐[(4‐bromophenylimino)methyl]phenol (BPIMP) with air and NaOCl oxidants in an aqueous alkaline medium between 50 and 90°C. The yield of OBPIMP was found to be 67 and 88% for air and NaOCl oxidants, respectively. Their structures were confirmed by elemental and spectral such as IR, ultraviolet–visible spectrophotometer (UV–vis), ¹H‐NMR, and ¹³C‐NMR analyses. The characterization was made by TG‐DTA, size exclusion chromatography, and solubility tests. The resulting complexes were characterized by electronic and IR spectral measurements, elemental analysis, AAS, and thermal studies. According to TG analyses, the weight losses of OBPIMP, and oligomer‐metal complexes with Co⁺², Ni⁺², and Cu⁺² ions were found to be 93.04%, 59.80%, 74.23%, and 59.30%, respectively, at 1000°C. Kinetic and thermodynamic parameters of these compounds investigated by Coats‐Redfern, MacCallum‐Tanner, and van Krevelen methods. The values of the apparent activation energies of thermal decomposition (E_a), the reaction order (n), preexponential factor (A), the entropy change (ΔS*), enthalpy change (ΔH*), and free energy change (ΔG*) obtained by earlier‐mentioned methods were all good in agreement with each other. It was found that the thermal stabilities of the complexes follow the order Cu(II) > Co(II) > Ni(II). © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synergistic extraction of rare earths(III) from chloride medium with mixtures of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate

The synergistic effect of 1‐phenyl‐3‐methyl‐4‐benzoyl‐pyrazalone‐5 (HPMBP, HA) and di‐(2‐ethylhexyl)‐2‐ethylhexylphosphonate (DEHEHP, B) in the extraction of rare earths (RE) from chloride solutions has been investigated. Under the experimental conditions used, there was no detectable extraction when DEHEHP was used as a single extractant while the amount of RE(III) extracted by HPMBP alone was also low. But mixtures of the two extractants at a certain ratio had very high extractability for all the RE(III). For example, the synergistic enhancement coefficient was calculated to be 9.35 for Y³⁺, and taking Yb³⁺ and Y³⁺ as examples, RE³⁺ is extracted as RE(OH)A₂.B. The stoichiometry, extraction constants and thermodynamic functions such as Gibbs free energy change ΔG (?17.06 kJ mol^?1), enthalpy change ΔH (?35.08 kJ mol^?1) and entropy change ΔS (?60.47 J K^?1 mol^?1) for Y³⁺ at 298 K were determined. The separation factors (SF) for adjacent pairs of rare earths were calculated. Studies show that the binary extraction system not only enhances the extraction efficiency of RE(III) but also improves the selectivity, especially between La(III) and the other rare earth elements. Copyright © 2006 Society of Chemical Industry     

Synthesis,characterization, and antimicrobial properties of oligo‐4‐[(pyridine‐3‐yl‐methylene) amino] phenol

The oxidative polycondensation reaction conditions of 4‐[(pyridine‐3‐yl‐methylene) amino]phenol (4‐PMAP) were studied using H₂O₂, atmospheric O₂, and NaOCl oxidants in an aqueous alkaline medium between 30°C and 90°C. Synthesized oligo‐4‐[(pyridine‐3‐yl‐methylene) amino] phenol (O‐4‐PMAP) was characterized by ¹H‐, ¹³C NMR, FTIR, UV–vis, size exclusion chromatography (SEC), and elemental analysis techniques. The yield of O‐4‐PMAP was found to be 32% (for H₂O₂ oxidant), 68% (for atmospheric O₂ oxidant), and 82% (for NaOCl oxidant). According to the SEC analysis, the number–average molecular weight, weight–average molecular weight, and polydispersity index values of O‐4‐PMAP was found to be 5767, 6646 g mol^?1, and 1.152, respectively, using H₂O₂, and 4540, 5139 g mol^?1, and 1.132, respectively, using atmospheric O₂, and 9037, 9235 g mol^?1, and 1.022, using NaOCl, respectively. According to TG and DSC analyses, O‐4‐PMAP was more stable than 4‐PMAP against thermal decomposition. The weight loss of O‐4‐PMAP was found to be 94.80% at 1000°C. Also, antimicrobial activities of the oligomer were tested against B. cereus, L. monocytogenes, B. megaterium, B. subtilis, E. coli, Str. thermophilus, M. smegmatis, B. brevis, E. aeroginesa, P. vulgaris, M. luteus, S. aureus, and B. jeoreseens. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3327–3333, 2006     

Synthesis and characterization of oligosalicylaldehyde‐graft‐oligoaniline and its beginning oligomers

Conjuge bonding oligosalicylaldehyde‐graft‐oligoaniline (OSA‐graft‐OA) was synthesized from the polycondensation reaction of oligosalicylaldehyde (OSA) with oligoaniline (OA). There were various functional groups such as ? OH, ? NH and ? CH?N in the structure of the graft cooligomer. The physical properties of graft‐co‐oligomers such as melting temperature and solubility were studied: number‐average molecular weight, mass‐average molecular weight, and a polydispersity index of OA, OSA, and fractions of the graft cooligomers [(OSA‐graft‐OA)‐I] and [(OSA‐graft‐OA)‐II] were found to be 740, 780 g mol^?1,1.05; 3700, 5990 g mol^?1, 1.62; 990, 2770 g mol^?1, 2.80 and 1300, 4100 g mol^?1, 3.15, respectively. The FTIR and UV‐Vis spectra of the graft cooligomer were compared with those of beginning oligomers. The spectral analyses results showed that the OSA‐graft‐OA synthesized from the polycondensation reaction of aromatic amine with aldehyde that have long oligophenol macromolecule bonded each other with an azomethine bridge through oligophenylamine side chains. The thermal stability of the graft cooligomer and oligomers were measured by thermogravimetric analysis (TG) under an air atmosphere. According to TG analyses, the carboneous residues of the [(OSA‐graft‐OA)‐I) (soluble in ethanol) and (OSA‐graft‐OA)‐II) (soluble in toluene)] were 23 and 40%, respectively, at 1000°C. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 218–226, 2002     

Synthesis of poly(ester‐anhydride)s based on poly(ϵ‐caprolactone) prepolymer

The objective of this study was to prepare high molecular weight poly(ester‐anhydride)s by melt polycondensation. The polymerization procedure consisted of the preparation of carboxylic acid terminated poly(?‐caprolactone) prepolymers that were melt polymerized to poly(?‐caprolactone)s containing anhydride functions along the polymer backbone. Poly(?‐caprolactone) prepolymers were prepared using either 1,4‐butanediol or 4‐(hydroxymethyl)benzoic acid as initiators, yielding hydroxyl‐terminated intermediates that were then converted to carboxylic acid‐terminated prepolymers by reaction with succinic anhydride. Prepolymers were then allowed to react with an excess of acetic anhydride, followed by subsequent polycondensation to resulting high molecular weight poly(ester‐anhydride)s. Upon coupling of prepolymers, size exclusion chromatography analyses showed an increase from 3600 to 70,000 g/mol in number‐average molecular weight (M_n) for the 1,4‐butanediol initiated polymer, and an increase from 7200 to 68,000 g/mol for the 4‐(hydroxymethyl)benzoic acid‐initiated polymer. 4‐Hydroxybenzoic acid and adipic acid were also used as initiators in the preparation of poly(?‐caprolactone) prepolymers. However, with these initiators, the results were not satisfactory. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 176–185, 2001     

Synthesis and characterization of imine polymers containing aliphatic and aromatic groups and some of Schiff base‐metal complexes

In this study, the oxidative polycondensation reaction conditions of 2,2′‐[(2,5‐dichloro‐1,4‐phenylene)bisnitrilomethylylidene]diphenol (DCPMDP) were studied between 40 and 90°C using different times and concentrations in the alkaline medium to determine effect on the yield of these parameters. Polymerization of 2,2′‐piperazine‐1,4‐diylbis[propane‐3,1‐diylnitrilomethylylidene]diphenol (PDMDP) was performed at two steps with graft polycondensation method. Additionally, seven different metal complexes were also synthesized from PDMDP with some metal salts. The structures of the compounds were confirmed by UV–vis, FT‐IR, ¹H and ¹³C NMR spectroscopy analyses. The characterization was made by TG‐DTA, size exclusion chromatography (SEC), elemental analysis, and solubility tests. HOMO‐LUMO energy levels and electrochemical band (E_g′) gaps were determined from cyclic voltammetry (CV) measurements. Also, optical band (E_g) gaps were calculated from UV–vis measurements. Electrical conductivity of doped and undoped monomer and oligomer were measured by four‐point probe technique using an electrometer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Synthesis,physical properties,and crystallization of optically active poly(L‐phenyllactic acid) and poly(L‐phenyllactic acid‐co‐L‐lactic acid)

Optically active poly(L ‐phenyllactic acid) (Ph‐PLLA), poly(L ‐lactic acid) (PLLA), and poly(L ‐phenyllactic acid‐co‐L ‐lactic acid) with weight‐average molecular weight exceeding 6 × 10³ g mol^?1 were successfully synthesized by acid catalyzed direct polycondensation of L ‐phenyllactic acid and/or L ‐lactic acid in the presence of 2.5–10 wt % of p‐toluenesulfonic acid. Their physical properties and crystallization behavior were investigated by differential scanning calorimetry, thermogravimetry, and polarimetry. The absolute value of specific optical rotation ([α]) for Ph‐PLLA (?38 deg dm^?1 g^?1 cm³) was much lower than that of [α] for PLLA (?150 deg dm^?1 g^?1 cm³), suggesting that the helical nature was reduced by incorporation of bulky phenyl group. PLLA was crystallizable during solvent evaporation, heating from room temperature, and cooling from the melt. Incorporation of a very low content of bulky phenyllactyl units even at 4 mol % suppressed the crystallization of L ‐lactyl unit sequences during heating and cooling, though the copolymers were crystallizable for L ‐phenylactyl units up to 6 mol % during solvent evaporation. The activation energy of thermal degradation (ΔE_td) for Ph‐PLLA (200 kJ mol^?1) was higher than that for PLLA (158 kJ mol^?1). The ΔE_td for the copolymers increased with an increase in L ‐phenyllactyl unit content. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Gadolinium‐conjugated FA‐PEG‐PAMAM‐COOH nanoparticles as potential tumor‐targeted circulation‐prolonged macromolecular MRI contrast agents

The aim of research is to develop potential tumor‐targeted circulation‐prolonged macromolecular magnetic resonance imaging (MRI) contrast agents without the use of low molecular gadolinium (Gd) ligands. The contrast agents were based on polymer–metal complex nanoparticles with controllable particle size to achieve the active and passive tumor‐targeted potential. In particular, poly (amidoamine) (PAMAM) dendrimer with 32 carboxylic groups was modified with folate‐conjugated poly (ethyleneglycol) amine (FA‐PEG‐NH₂, M_w: 2 k and 4 kDa). FA‐PEG‐PAMAM‐Gd macromolecular MRI contrast agents were prepared by the complex reaction between the carboxylic groups in PAMAM and GdCl₃. The structure of FA‐PEG‐PAMAM‐COOH was confirmed by nuclear magnetic resonance (¹H‐NMR), Fourier transform infrared (FTIR) spectra, and electrospray ionization mass spectra (ESI‐MS). The mass percentage content of Gd (III) in FA‐PEG‐PAMAM‐Gd was measured by inductively coupled plasma‐atomic emission spectrometer (ICP‐AES). The sizes of these nanoparticles were about 70 nm measured by transmission electron microscopy, suggestion of their passive targeting potential to tumor tissue. In comparison with clinically available small molecular Gadopentetate dimeglumine, FA‐PEG‐PAMAM‐Gd showed comparable cytotoxicity and higher relaxation rate, suggestion of their great potential as tumor‐targeted nanosized macromolecular MRI contrast agents due to the overexpressed FA receptor in human tumor cell surfaces. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Poly(2‐acrylamido glycolic acid‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid): Synthesis,characterization, and retention properties for environmentally impacting metal ions

Poly(2‐acrylamido glycolic acid‐co‐2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) [P(AGA‐co‐APSA)] was synthesized by radical polymerization in an aqueous solution. The water‐soluble polymer, containing secondary amide, hydroxyl, carboxylic, and sulfonic acid groups, was investigated, in view of their metal‐ion‐binding properties, as a polychelatogen with the liquid‐phase polymer‐based retention technique under different experimental conditions. The investigated metal ions were Ag⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, and Cr³⁺, and these were studied at pHs 3, 5, and 7. P(AGA‐co‐APSA) showed efficient retention of all metal ions at the pHs studied, with a minimum of 60% for Co(II) at pH 3 and a maximum close to 100% at pH 7 for all metal ions. The maximum retention capacity (n metal ion/n polymer) ranged from 0.22 for Cd²⁺ to 0.34 for Ag⁺. The antibacterial activity of Ag⁺, Cu²⁺, Zn²⁺, and Cd²⁺ polymer–metal complexes was studied, and P(AGA‐co‐APSA)–Cd²⁺ presented selective antibacterial activity for Staphylococcus aureus with a minimum inhibitory concentration of 2 μg/mL. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and properties of novel poly(coumarin‐amide)s

A novel monomer diacid, 6,6′‐methylenebis(2‐oxo‐2H‐chromene‐3‐carboxylic acid), was synthesized and used in a direct polycondensation reaction with various aromatic diamines in N‐methyl‐2‐pyrrolidone solution containing dissolved LiCl and CaCl₂, using triphenyl phosphite and pyridine as condensing agents to give a series of novel heteroaromatic polyamides containing photosensitive coumarin groups in the main chain. Polyamide properties were investigated by DSC, TGA, GPC, wide‐angle X‐ray scattering, viscosity, and solubility measurements. The copolymers were soluble in aprotic polar solvents, and their inherent viscosities varied between 0.49 and 0.78 dL g^?1. The weight‐average and number‐average molecular weights, measured by gel permeation chromatography, were 27,500–43,900 g mol^?1 and 46,500–66,300 g mol^?1, respectively, and polydispersities in the range of 1.48–1.69. The aromatic polyamides showed glass‐transition temperatures (T_g) ranging from 283 to 329°C and good thermal properties evidenced by no significant weight loss up to 380°C and 10% weight loss recorded above 425°C in air. All the polyamides exhibited an amorphous nature as evidenced by wide‐angle X‐ray diffraction and demonstrated a film forming capability. Water uptake values up to 3.35% were observed at 65% relative humidity. These polymers exhibited strong UV‐vis absorption maxima at 357–369 nm in DMSO solution, and no discernible photoluminescence maxima were detected by exciting with 365 nm. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Synthesis, Characterization and Anti-microbial Activity of Oligo-N-2-aminopyridinylsalicylaldimine and Some Oligomer-metal Complexes

The oxidative polycondensation and optimum reaction conditions of N-2-aminopyridinylsalicylaldimine using air oxygen, H₂O₂ and NaOCl were determined in an aqueous alkaline solution between 40–90°C. Oligo-N-2-aminopyridinylsalicylaldimine (OAPSA) was characterized by using ¹H-NMR, FT-IR, UV-vis and elemental analysis. N-2-aminopyridinylsalicylaldimine was converted to oligomer by oxidizing in an aqueous alkaline medium. The number average molecular weight (M _n), weight average molecular weight (M _w) and polydispersity index (PDI) values were found to be 7487 gmol^–1, 7901 gmol^–1 and 1.06, respectively. According to these values, 70% of N-2-aminopyridinylsalicylaldimine turned into oligo-N-2-aminopyridinylsalicylaldimine. During the polycondensation reaction, a part of the azomethine (–CH=N–) groups oxidized to carboxylic (–COOH) group. Besides, the structure and properties of oligomer-metal complexes of oligo-N-2-aminopyridinyl salicylaldimine (OAPSA) with Cu (II), Ni (II), and Co (II) were studied by FT-IR, UV-vis DTA, TG and elemental analysis. Anti-microbial activities of the oligomer and its oligomer-metal complexes have been tested against C. albicans, L. monocytogenes, B. megaterium, E. coli, M. smegmatis, E. aeroginesa, P. fluorescen and B. jeoreseens. Also, according to the TG and DTA analyses, oligo-N-2-aminopyridinylsalicylaldimine and its oligomer-metal complexes were found to be stable thermo-oxidative decomposition. The weight loss of OAPSA found to be 20%, 50% and 98% at 350°C, 535°C and 1000°C, respectively.     

Synthesis,properties and pyrolysis of siloxane‐ and imide‐modified epoxy resin cured with siloxane‐containing dianhydride

Hydrosilylation of nadic anhydride with tetramethyl disiloxane yielded 5,5′‐(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboxylic anhydride (I), which further reacted with 4‐aminophenol to give N,N′‐bis(4‐hydroxyphenyl)‐5,5′‐bis‐(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboximide (II). Epoxidation of II with excess epichlorohydrin formed a siloxane‐ and imide‐modified epoxy oligomer (ie diglycidyl ether of N,N′‐bis(4‐hydroxyphenyl)‐5,5′‐bis(1,1,3,3‐tetramethyl disiloxane‐1,3‐diyl)‐bis‐norborane‐2,3‐dicarboximide) (III). Equivalent ratios of III/I of 1/1 and 1/0.8 were prepared and cured to produce crosslinked materials. Thermal mechanical and dynamic mechanical properties were investigated by TMA and DMA, respectively. It was noted that each of these two materials showed a glass transition temperature (T_g) higher than 160 °C with moderate moduli. The thermal degradation kinetics was studied with dynamic thermogravimetric analysis (TGA) and the estimated apparent activation energies were 111.4 kJ mol^?1 (in N₂), 117.1 kJ mol^?1 (in air) for III/I = 1/0.8, and 149.2 kJ mol^?1 (in N₂), 147.6 kJ mol^?1 (in air) for III/I = 1/1. The white flaky residue of the TGA char was confirmed to be silicon dioxide, which formed a barrier at the surface of the polymer matrix and, in part, accounted for the unique heat resistance of this material. Copyright © 2005 Society of Chemical Industry     

Synthesis,extraction, and anti‐bacterial studies of some new bis‐1,2,4‐triazole derivatives part I

A series of new bis triazole Schiff base derivatives (4) were prepared in good yields by treatment of 4‐amino‐3,5‐diphenyl‐4H‐1,2,4‐triazole (3) with bisaldehydes (1). Schiff bases (4) were reduced with NaBH₄ to afford the corresponding bisaminotriazoles (5). All the new compounds were characterized by IR, ¹H NMR and ¹³C NMR spectral data. Their overall extraction (log K_ex) constants for 1 : 1 (M : L) complexes and CHCl₃/H₂O systems were determined at 25 ± 0.1°C to investigate the relationship between structure and selectivity toward various metal cations. The extraction equilibrium constants were estimated using CHCl₃/H₂O membrane transfer with inductively coupled plasma‐atomic emission spectroscopy spectroscopy. The stability sequence of the triazole derivatives in CHCl₃ for the metal cations was exhibited a characteristic preference order of extractability to metal ions [Fe(III) > Cu(II) > Pb(II) > Co(II) > Ni(II) > Mn(II) > Zn(II) > Mg(II) > Ca(II)]. The compounds were tested for anti‐microbial activity applying agar diffusion technique for 11 bacteria. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Schiff base‐substituted polyphenol: synthesis,characterisation and non‐isothermal degradation kinetics

BACKGROUND: Polymers of phenols and aromatic amines have emerged as new materials in fields such as superconductors, coatings, laminates, photoresists and high‐temperature environments. The stability, kinetics and associated pollution of the thermal decomposition of oligophenols are of interest for the aforementioned fields. RESULTS: A new Schiff base polymer, derived from N,N′‐bis(2‐hydroxy‐3‐methoxyphenylmethylidene)‐2,6‐pyridinediamine, was prepared by oxidative polycondensation. Characterisations using Fourier transform infrared, UV‐visible, ¹H NMR and ¹³C NMR spectroscopy, thermogravimetric/differential thermal analysis, gel permeation chromatography, cyclic voltammetry and conductivity measurements were performed. The number‐average (M_n) and weight‐average molecular weight (M_w) and dispersity (D = M_w/M_n) of the polymer were found to be 61 000 and 94 200 g mol^?1 and 1.54, respectively. Apparent activation energies of the thermal decomposition of the polymer were determined using the Tang, Flynn–Wall–Ozawa, Kissinger–Akahira–Sunose and Coats–Redfern methods. The most likely decomposition process was a D_n deceleration type in terms of the Coats–Redfern and master plot results. CONCLUSION: The mechanism of the degradation process can be understood through the use of kinetic parameters obtained from various non‐isothermal methods. Copyright © 2009 Society of Chemical Industry     

Towards improving wet‐adhesion in a metal oxide‐polymer coating system

An investigation using a variable radius roll adhesion test (VaRRAT) revealed an irreversible increase in the wet‐adhesion in a metal–oxide–polymer system, under specific experimental conditions. This observation is further confirmed by the T_g measurements and the ATR‐FTIR studies. The increase in wet‐adhesion is attributed to late H₂O‐catalyzed curing of the previously partially cured polymers (epoxy ring opening), as well as the formation of nanocomposite layer within the epoxy primer matrix, because of precipitation of the nanocrystals including zinc ammine complexes formed as a result of dissolution of the zinc/aluminum alloy as well as the metal oxide pigments by the amine crosslinker. High activation energy of ～100 kJ mol^?1 indicated a chemical process to be responsible for the adhesion gain. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 99: 3318–3327, 2006     

Melt polycondensation of L‐lactic acid to poly(L‐lactic acid) with Sn(II) catalysts combined with various metal alkoxides

Melt polycondensation of L ‐lactic acid (LA) was examined in the presence of binary catalyst systems consisting of SnCl₂·2H₂O and metal alkoxides as co‐catalysts. Among the co‐catalysts examined, viz (Al(O ⁱPr)₃,Ti(O ⁱPr)₄,Y(O ⁱPr)₃,Si(OEt)₄ and Ge(OEt)₄), Ge(OEt)₄ was found to be the most effective in enhancing the catalytic activity of Sn(II). With an optimized composition of SnCl₂·2H₂O–Ge(OEt)₄, the molecular weight (M_n) of PLLA reached 40 000 Da in a short reaction time (<15 h) at the optimum reaction conditions of 180 °C and 10 Torr. This catalyst system was also superior to the conventional single metal ion catalysts such as Sn(II) in terms of racemization and discolouration of the resultant polymer. The metal alkoxides, added as co‐catalysts, should work as oxo acids that can effectively control the catalytic activity of Sn(II) ion in the direct polycondensation of LA, in a manner similar to that of proton acids. © 2003 Society of Chemical Industry     

Synthesis of star‐shaped poly(ϵ‐caprolactone) by samarium‐based tetrafunctional initiator and its dilute‐solution properties

An in situ–generated tetrafunctional samarium enolate from the reduction of 1,1,1,1‐tetra(2‐bromoisobutyryloxymethyl)methane with divalent samarium complexes [Sm(PPh₂)₂ and SmI₂] in tetrahydrofuran has proven to initiate the ring‐opening polymerization of ?‐caprolactone (CL) giving star‐shaped aliphatic polyesters. The polymerization proceeded with quantitative conversions at room temperature in 2 h and exhibited good controllability of the molecular weight of polymer. The resulting four‐armed poly(?‐caprolactone) (PCL) was fractionated, and the dilute‐solution properties of the fractions were studied in tetrahydrofuran and toluene at 30°C. The Mark–Houwink relations for these solvents were [η] = 2.73 × 10^?2M_w^0.74 and [η] = 1.97 × 10^?2M_w^0.75, respectively. In addition, the unperturbed dimensions of the star‐shaped PCL systems were also evaluated, and a significant solvent effect was observed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 175–182, 2006     

Study on Synthesis, Characterization, Thermal Stability and Conductivity Properties of a New Conjugated Oligoazomethine and some of its Metal Complexes

A novel azomethine oligomer of 2,3-bis[(2-hydroxyphenyl)methylene]diaminopyridine (HPMDAP) was first synthesized by oxidative polycondensation reaction using air and NaOCl as oxidative agents. Optimum reaction conditions for the oxidative polycondensation and the main parameters of the process were established. At optimum reaction conditions, the yield of the product was found to be 69%. Oligomeric complexes of 2,3-bis[(2-hydroxyphenyl)methylene]diaminopyridine with Cd(II), Co(II), Cu(II), Ni(II), Fe(II), Pb(II), Cr(III) and Zn(II) were successfully prepared. Structures of monomer, oligomer and some oligomer metal complexes obtained were confirmed by FT-IR, UV–vis, ¹H- and ¹³C-NMR and elemental analysis. Characterization was carried out by TG-DTA, size exclusion chromatography (SEC), magnetic moment and solubility tests. The ¹H- and ¹³C-NMR data showed that polymerization proceed by C–C coupling of ortho and para positions according to –OH group of HPMDAP. Elemental analysis of chelates suggests that the metal ligand ratio is about 1:2. Molecular weight distribution values of the products were determined by size exclusion chromatography (SEC). According to TG analyses, the carbonaceous residues of HPMDAP and OHPMDAP were found to be 34.94 and 29.36% at 1000 °C, respectively. Thermal analyses of Cd, Co, Cu, Ni, Fe, Pb, Cr and Zn oligomer–metal complexes were also investigated under N₂ atmosphere between 15 and 1000 °C. Electrical conductivities of OHPMDAP and its metal complexes were also measured with four probe technique.     

Structural and Preliminary Explosive Property Characterizations of New 3,4,5‐Triamino‐1,2,4‐triazolium (Guanazinium) Salts

Two new highly stable energetic salts were synthesized in reasonable yield by using the high nitrogen‐content heterocycle 3,4,5‐triamino‐1,2,4‐triazole and resulting in its picrate and azotetrazolate salts. 3,4,5‐Triamino‐1,2,4‐triazolium picrate (1) and bis(3,4,5‐triamino‐1,2,4‐triazolium) 5,5′‐azotetrazolate (2) were characterized analytically and spectroscopically. X‐ray diffraction studies revealed that protonation takes place on the nitrogen N1 (crystallographically labelled as N2). The sensitivity of the compounds to shock and friction was also determined by standard BAM tests revealing a low sensitivity for both. B3LYP/6–31G(d, p) density functional (DFT) calculations were carried out to determine the enthalpy of combustion (Δ_cH (1) =−3737.8 kJ mol⁻¹, Δ_cH (2) =−4577.8 kJ mol⁻¹) and the standard enthalpy of formation (Δ_fH° (1) =−498.3 kJ mol⁻¹, (Δ_fH° (2) =+524.2 kJ mol⁻¹). The detonation pressures (P (1) =189×10⁸ Pa, P (2) =199×10⁸ Pa) and detonation velocities (D (1) =7015 m s⁻¹, D (2) =7683 m s⁻¹) were calculated using the program EXPLO5.     

Ring‐opening metathesis polymerization of norbornene catalyzed by tantalum and niobium complexes with chelating O‐donor ligands

BACKGROUND: In comparison with group 6 transition metals, such as tungsten and molybdenum, and group 8 metal ruthenium, group 5 metal‐based catalysts for ring‐opening metathesis polymerization (ROMP) have remained much less studied. The few reported ROMP catalysts of group 5 metals require multiple reaction steps to be synthesized, and are highly sensitive to air and moisture. RESULTS: A series of pentavalent tantalum and niobium complexes having catecholato, tropolonato, hinokitiolato, biphenolato and binaphtholato ligands were prepared and their catalytic activities for the ROMP of norbornene (NBE) were studied in the presence of trialkylaluminium as a co‐catalyst. Among these complexes, the tantalum complexes showed high activity upon activation with Buⁱ₃Al. In sharp contrast, the niobium complexes were effectively activated with Me₃Al. The polymers obtained with these complexes had high molecular weights (M_n > 10⁵ g mol⁻¹) and relatively narrow molecular weight distributions (M_w/M_n ≈ 2). CONCLUSION: We found that easily accessible and relatively stable tantalum and niobium complexes with such chelating O‐donor ligands showed high catalytic activity for ROMP of NBE depending on the kind of co‐catalyst. These findings could contribute to future development of ROMP catalysts. Copyright © 2008 Society of Chemical Industry