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A series of soluble thermosetting polyimide resins containing benzoxazole structure were synthesized by two-step polymerization using 4-phenylethynylphthalic anhydride (4-PEPA) as the end-capping reagent, 2-(4-aminophenyl)-5-aminobenzoxazole (BOA) and 3,4′-diaminodiphenyl ether (3,4′-ODA) as the aromatic diamines, and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) as the aromatic dianhydride. The imide oligomers were characterized by employing Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), solubility tests and rheological measurements. Thermosetting polyimides derived from the imide oligomers were then produced via a thermal cross-linking reaction of the phenylethynyl group. The thermal and mechanical properties of the thermosets were studied using thermogravimetric analysis (TGA), dynamic mechanical thermal analysis (DMA), and mechanical property measurements. The effects of chemical architectures and molecular weights of the imide oligomers on processability, thermostability and mechanical properties were systematically investigated. The results showed that all the copolymerized imide oligomers possessed good solubility in organic and low melt viscosity, and the corresponding thermosets exhibited high glass transition temperature (up to 401°C) and 5% weight-loss temperature (up to 533°C) in an air atmosphere while excellent mechanical properties (flexural strength up to 217 MPa and elongation at break up to 11.2%). With the increase of the concentration of the benzoxazole group, the imide oligomers of PI-X-2 (-O-, -BO-, -B-) exhibited less solubility and higher minimum melt viscosity but improved glass transition temperature after curing and mechanical properties of their thermosets.

In this study, three adamantane-containing diamines, i.e. 1,3-bis(4-aminophenyl) adamantane (ADMDA), 1,3-bis(3,5-dimethyl-4-aminophenyl) adamantane (DMADMDA) and 1,3-bis(fluoro-aminophenyl) adamantane (FADMDA), were successfully synthesized by Friedel–Crafts alkylation reactions between 1-adamantanol and acetanilide or its analogues, followed by hydrolysis with aqueous NaOH solution. Three regio-isomers were formed in the case of FADMDA due to the occurrence of both para- and ortho-alkylation (relative to the amino groups). Three series of semi-alicyclic polyimides were subsequently produced through a conventional one-step solution polycondensation between the as-developed diamines and commercial dianhydrides. The properties of the synthesized polyimides were characterized with respect to their thermal, mechanical and optical properties. The adamantane-containing polyimides exhibited significantly high glass transition temperatures (Tg) in the range 285–440 °C, excellent optical transparency (>80% transmittance at 400 nm) and optimal thermal and mechanical properties. The substituents in diamines significantly impacted the properties of the resulting polyimides. Specifically, the polyimides from DMADMDA demonstrated higher d-spacing, higher Tg, lower coefficient of thermal expansion (CTE), better optical properties and inferior tensile properties relative to the ADMDA-derived polymers, which could be attributed to the enhanced chain rigidity and reduced inter- and intra-molecular interactions associated with the two bulky methyl groups. In contrast, the FADMDA-derived polymers exhibited lower d-spacing, lower Tg, higher CTE, higher tensile modulus and lower elongation at break than the ADMDA-based ones, due to the reduced chain linearity regularity caused by the ortho-alkylated isomers, as well as suppressed intramolecular interaction originating from the strongly electron-withdrawing fluorine atoms. The excellent comprehensive properties of the adamantane-containing polyimides render these materials promising candidates for a variety of optical and optoelectronic applications.

A novel dianhydride, 3,3′-di-tert-butyl-2,2′-dimethoxy-[1,1′-binaphthalene]-6,6′,7,7′-tetracarboxylic dianhydride (TNTDA), was prepared via a multi-step process. A model compound made using TNTDA and aniline has a dihedral angle of 75° between the two naphthalimide rings, evidenced by single crystal X-ray diffraction data. High temperature polycondensation of TNTDA with four different diamines afforded four intrinsically microporous polyimides (PIM-PIs). The fractional free volumes (FFV), surface areas, and average inter-chain distances of the polyimides were 0.181–0.214, 379–564 m2 g−1, and 0.635–0.682 nm, respectively. Furthermore, the rigid, bulky, and contorted structures of the PIM-PIs led to the formation of roughly 0.6 nm ultramicropores and roughly 1.2 nm larger micropores. The ultramicropores can improve the gas size-sieving capability of the polyimides, while the larger micropores can facilitate high permeability. Consequently, the TNTDA-based PIM-PIs showed an improved gas separation performance compared to polymers made using the benchmark monomer, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride. In particular, polymers from TNTDA and 2,6-diaminotriptycene (DAT) exhibited the best performance, with CO2/CH4 and O2/N2 separation metrics approaching or surpassing the 2008 Robeson upper bounds, because of the presence of additional ultramicropores related to the internal free volume of the triptycene moiety.

In order to improve the interfacial compatibility between the fibers and epoxy resins, polyimide (PI) fibers were modified using oxygen plasma with various treatment powers. The properties of PI fibers before and after surface modification were comparatively characterized according to their chemical composition, surface morphology, surface free energy, single filament tensile strength, and interfacial shear strength (IFSS). Most of the fiber properties, including the ratio of oxygen to nitrogen, oxygen concentration, surface free energy, and IFSS firstly increased with the plasma power, and then decreased when the plasma power was higher than 120 W. With a plasma power of 120 W, the oxygen concentration and the ratio of oxygen to carbon atoms (O/C) was 26% (22% for untreated fiber) and 0.38 (0.28 for untreated fiber), respectively. Meanwhile, the values of surface free energy and IFSS were 89% and 30% higher than those for untreated fiber, respectively. Furthermore, the values of single filament tensile strength for modified fibers were only 2.3% lower than those for pristine one. These results indicated that the compatibility between PI fibers and epoxy resins was greatly improved without compromising mechanical properties.

A series of imide resins were prepared using 2,3,3′,4′-oxydiphthalic dianhydride, 4-phenylethynylphthalic anhydride, and aromatic diamines (1, 3-bis(3-aminophenoxy), 3,4′-oxyaniline, 2,2′-bis (trifluoromethyl) benzidine, and m-phenylenediamine) as starting materials. These imide oligomers were characterized by means of Fourier transform infrared spectroscopy, differential scanning calorimetry, intrinsic viscosity measurements, and rheological measurements. Some of these oligomers exhibited low (2 h at 250°C) melt viscosity, which was highly desirable for resin transfer molding process. Thermosetting polyimides (PIs) were then produced from these oligomers via thermal cross-linking reaction of phenylethynyl group. The properties of the thermosets were studied using tensile and flexural testing, dynamic mechanical thermal analysis, and thermogravimetric analysis. The cured PIs exhibited a good combination of thermal and mechanical properties, with a tensile strength of 31–76 MPa, flexural strength of 38–142 MPa, glass transition temperatures of 233–358°C, and 5% weight loss temperatures of 540–545°C under nitrogen atmosphere.

The preparation and characterization of the compounds [HFe 4 (CO) 12 C] BXY (X=Y=H, Cl, Br; X=H, Y=Cl, Br, OH) are described. Geometric, spectroscopic, and Fenske-Hall quantum-chemical parameters demonstrate that these compounds are usefully described as tricoordinate boron compounds substituted with a carbido cluster. The carbido cluster [HFe 4 (CO) 12 C], as a substituent, is shown to be both a sterically demanding ligand and a strong π donor to the boron center. The unanticipated differences in the reactivity of these compounds with AlX 3 , NEt 3 , H 2 O, and THF as X and Y are varied reflect the unusual properties of this compound type. Single-crystal X-ray diffraction studies of [HFe 4 (CO) 12 C]BHX (X=Cl, Br) are reported

A mechanistic hypothesis of metallaborane cluster build-up by the condensation of metal and boron containing fragments, which is supported by circumstantial evidence from previous work, suggests improved routes to the synthesis of ferraboranes. This work describes two new approaches consisting of the examination of two precursors with properties consistent with such a hypothesis. The first precursor, a neutral mononuclear dimethyl sulfide substituted iron tetracarbonyl, Fe(CO) 4 SMe 2 , is a new compound and the high yield synthesis and structural characterization of it are reported. This compound provides a better route to the ferraborane Fe 2 (CO) 6 B 2 H 6 than those presently known and is an isolatable, alternate source of the Fe(CO) 4 fragment. The second precursor, Fe(CO) 3 (cco) 2 , where cco is η 2 - cis -cyclooctene, is a known, ready source of the Fe(CO) 3 fragment. The reaction of Fe(CO) 3 (cco) 2 with BH 3 sources at low temperatures results in good yields of known ferraboranes and a product distribution that depends primarily on the ratio of boron to iron in the reactants. Both of these results support a mechanism for metallaborane cluster formation involving rapid metal carbonyl fragment condensation as a principal mechanistic component.

The synthesis and structural characterization of the first example of a boracyclopropene ring coordinated to a trimetal fragment, Fe 3 (CO) 9 [C 3 -B(H)C(H)C(Me)], are described. The compound constitutes an example of a cluster containing three transition metals that can only be reasonably considered as a six-atom cluster containing three iron, two carbon, and one boron atoms. This particular derivative of the cluster core also constitutes an example of a chiral cluster

Etude de la conversion de (μ-H) 3 Fe 3 (CO) 9 (μ 3 -CCH 3 ) en (μ-H)Fe 3 (CO) 9 (μ-CO)CCH 3 et de la reaction inverse