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This mini-review summarizes the latest accomplishments with group 6 metal alkylidene-N-heterocyclic carbene complexes (metal = Mo, W) for use in olefin metathesis. Both the fundamentals and the unique features of this novel class of olefin metathesis catalysts are presented. Also, their use and performance in ring-closing metathesis, cross metathesis, homometathesis, and self-metathesis reactions as well as in ring-opening metathesis polymerization and cyclopolymerization is outlined.

We synthesized the first N-heterocyclic carbene (NHC) complexes of Schrock's molybdenum imido alkylidene bis(triflate) complexes. Unlike existing bis(triflate) complexes, the novel 16-electron complexes represent metathesis active, functional-group-tolerant catalysts. Single-crystal X-ray structures of two representatives of this novel class of Schrock catalysts are presented and reactivity is discussed in view of their structural peculiarities. In the presence of monomer (substrate), these catalysts form cationic species and can be employed in ring-closing metathesis (RCM), ring-opening metathesis polymerization (ROMP), as well as in the cyclopolymerization of α,ω-diynes. Monomers containing functional groups, which are not tolerated by the existing variations of Schrock's catalyst, e.g., sec-amine, hydroxy, and carboxylic acid moieties, can be used. These catalysts therefore hold great promise in both organic and polymer chemistry, where they allow for the use of protic monomers.

A series of poly(arylene ether)s (7a–7f) were successfully synthesized by aromatic nucleophilic substitution reactions of imidoaryl biphenol (5), 4,9-bis-(4-hydroxy-phenyl)-2-phenyl-benzo[f]isoindole-1,3-dione with six different trifluoromethyl substituted bisfluoro monomers (6a–6f). The weight-average molar masses of the polymers were up to 280 kD as measured by GPC. These poly(arylene ether)s exhibited glass transition temperatures up to 361°C in DSC. These polymers showed very high thermal stability up to 558°C for 10% weight loss under synthetic air in TGA. Except 7d–7f, remaining polymers 7a–7c were soluble in a wide range of organic solvents. Transparent thin films of these polymers cast from DCM or NMP exhibited tensile strengths up to 75 MPa and elongation at break up to 41% depending on their exact repeating unit structures. These poly(arylene ether)s showed cut-off wavelength in between 400 and 450 nm except 7d and water absorption were in the range of 0.4 to 0.6%. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Silica-supported cationic Mo-imido alkylidene N-heterocyclic carbene catalysts, prepared by surface organometallic chemistry, display contrasting olefin metathesis activity for terminal and internal olefins. The high metathesis activity towards terminal alkenes is attributed to the strong σ-donating property of the NHC ancillary ligand, which disfavors the formation of the parent square-planar metallacyclobutane, an off-cycle reaction intermediate resulting from the reaction with ethylene, one of the metathesis products. This tailored ligand environment also allowed the first trigonal bipyramidal (TBP) metallacyclobutane reaction intermediate for supported Mo metathesis catalysts to be identified.

A new series of fluorinated poly(ether imide)s (PEIs) was synthesized from the bis(ether amine), 6,6′-bis-[2″-trifluoromethyl 4″-(4‴-aminophenyl)phenoxy]-3,3,3′,3′-tetramethyl-1,1′-spirobiindane containing rigid spiro-biindane unit with different aromatic dianhydrides, e.g., BPADA, 6-FDA, BTDA, ODPA and PMDA. All the PEIs were well characterized by elemental analysis, NMR, FTIR spectroscopy and gel permeation chromatography (GPC). Significant characterizations of their physical properties were done to assess their applicability as membranes for gas separation application. The PEIs exhibited excellent thermo-oxidative stability (409–491 °C for 5% weight loss), high glass transition temperatures (232–288 °C) and high tensile strengths (up to 60 MPa). Gas transport properties of the PEI membranes were systematically investigated at three different temperatures (35, 45 and 55 °C) under an applied upstream pressure of 3.5 bar. PEI ‘8b’ containing hexafluoroisopropylidene (6-FDA) unit showed the highest permeability coefficient in barrer for all the gases (PCO2 = 52.98, PO2 = 36.08) whereas PEI ‘8a’ exhibited the highest permselectivity towards CO2 relative to CH4 (68.2) and PEI ‘8d’ showed the highest permselectivity towards O2 over N2 (11.67) among the series. All the membranes exhibited excellent separation performance for O2/N2 gas pair surpassing the latest upper boundary limit drawn by L.M. Robeson. The effect of the presence of the cardo spiro-biindane unit and structural variations of the aromatic dianhydrides in these poly(ether imide) membranes towards the glass transition temperatures and fractional free volume (FFV) of the polymers and their consequences on gas permeation of four gases (e.g., CO2, O2, N2 and CH4) and permselectivity for pair of gases were correlated. Temperature dependencies of the permeation and diffusion processes were utilized to calculate the activation energies of the permeation and diffusion processes for these four different gases through these PEI membranes.

Four new poly(imide siloxane)s copolymers have been prepared by the reaction of 4,4′-(4,4′-isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) with commercially available 4,4′-oxydianiline (ODA) and amino-propyl terminated polydimethylsiloxane (APPS). The copolymers were synthesized with variation of the APPS loading of 5, 10, 15 and 20 wt% (2.20, 4.55. 7.07 and 9.85 mol%), respectively. The poly(imide siloxane)s have been well characterized by different spectroscopic, thermal, mechanical, surface and gas transport techniques. The synthesized polymers exhibit good solubility in different organic solvents. The polymers with 5, 10, 15 and 20 wt% siloxane loading show very good thermal stability in the range of 464–410 °C for 5% weight loss in synthetic air and glass transition temperatures in the range of 201–169 °C. All poly(imide siloxane)s form tough, transparent, and hydrophobic films, with tensile strength up to 65 MPa, a modulus of elasticity up to 1.42 GPa, elongation at break up to 25% and showing water contact angles up to 102°. Thermal, mechanical, surface and gas transport properties of these polymers have been evaluated and compared with the homopolyimide without siloxane moiety. The permeability, diffusion and solubility coefficients for the gases as well as the ideal separation factors for gas pairs have been determined. The poly(imide siloxane) with 20 wt% (9.85 mol%) siloxane shows the best compromise with very high permeability and a still high permselectivity for the CO2/CH4 gas pair.

A series of polyimide-POSS (PI-POSS) nanocomposite membranes were prepared using aminoethylaminopropylisobutyl group functionalized polyhedral oligomeric silsesquioxanes (POSS) as nanofiller. The membranes were characterized by DSC, TGA, AFM, FESEM, XRD, etc. The effects of incorporation of POSS into the four structurally different fluorinated polyimide membranes on their gas transport properties with four gases (CH4, N2, O2 and CO2) were investigated at 35 °C and at an applied pressure of 3.5 atm. All the nanocomposite membranes showed comparable glass transition temperature values but a little lower thermo-oxidative stability compared to their corresponding untreated polyimide membranes. The Young's modulus and maximum stress values of the polyimide-POSS membrane were slightly higher than those of the virgin polyimide membranes; however the elongation at break values were lower. POSS nanoparticles were well distributed as observed from FESEM image and AFM study exhibited no significant increase of the roughness of the hybrid membranes. The order of permeability of these gases were found as CO2 > O2 > N2 > CH4. The permeability of all the gases through the composite membranes increased significantly with comparable selectivity for different gas pairs, e.g., CO2/CH4 and O2/N2.

Gas transport properties of five new fluorinated poly(ether imide) (PEI) films containing cardo phthalimidine moiety in the main chain were systematically investigated at three different temperatures (35, 45 and 55 °C) under an applied upstream pressure of 3.5 bar. The effect of presence of the cardo phthalimidine unit and structural variations of five aromatic dianhydrides in these poly(ether imide) (PEI) films towards the gas permeation of four gases (e.g., CO 2 , O 2 , N 2 and CH 4 ) and their permselectivity for pair of gases were investigated. The films were prepared by the thermal imidization of the poly(amic acid)s of the reaction products of a new fluorinated diamine, 3,3-bis-[4-{2′-trifluoromethyl 4′-(4″-aminophenyl)phenoxy}phenyl]-2-phenyl-2,3-dihydro-isoindole-1-one with five different dianhydrides namely, BPADA, 6-FDA, BTDA, ODPA and PMDA. All the PEI films exhibited significantly high permeability coefficients than those of common glassy polymers, e.g., cellulose acetate, polysulfone and polycarbonate as well as to other polymers based on cardo phenolphthalein or phthalimide or phthalimidine moiety. PEI-II and PEI-V showed exceptionally high permeability coefficient for all the gases ( P C O 2 = 53.85,39.57 Barrers, respectively) along with higher permselectivity towards CO 2 relative to CH 4 (53.32 and 50.09, repectively) in comparison to cardo phthalimidine based non-flourinated poly(arylene ether sulfones) reported previously. Moreover, high permeability coefficients for O 2 ( P O 2 = 10.23,7.62 Barrers, respectively) and comparable permselectivities towards O 2 relative to N 2 (4.4–6.35) made these series of PEI films highly interesting in comparison to the previously reported phthalimidine based poly(arylene ether sulfone)s or poly(arylene ether ketone)s. Temperature dependency of the permeation and diffusion processes enables to calculate the activation energies of the permeation and diffusion processes for these four different gases through these five PEI films. An attempt has been taken to draw a structure–property correlationship between the repeat unit structures or the functional groups present, and the gas transport properties of this series of PEI films.

Several new poly(imide siloxane)s co-polymers have been prepared by the reaction of 4,4′-(hexafluoroisopropylidene)diphthalic anhydride (6FDA) with commercially available 4,4′-oxydianiline (ODA) and with five different novel trifluoromethyl-substituted diamines, each with 20 wt% aminopropyl-terminated polydimethylsiloxane (APPS). The poly(imide siloxane)s are well characterized by different spectroscopic, thermal, mechanical and electrical techniques. The synthesized polymers exhibit good solubility in different organic solvents. The 1H-NMR indicates that the siloxane incorporation is about 17–19% for polymers 1a–f. These poly(imide siloxane) films show low water absorption rate (0.88–0.09%) and a low dielectric constant (2.43–2.58) at 1 MHz. The polymers show very good thermal stability, even up to 419°C for 5% weight loss in synthetic air and a glass transition temperature of up to 230°C. All poly(imide siloxane)s formed tough transparent films, with a tensile strength of up to 79 MPa, a modulus of elas...

A new AB type of monomer 4′-fluoro-3,5-dimethyl-3′-trifluoromethyl-biphenyl-4-ol has been synthesized that leads to a new poly(arylene ether) by self polycondensation reaction. The monomer and the polymer have been well characterized by elemental analyses, FT-IR and NMR spectroscopy. Both FT-IR and NMR spectra of the polymers did not show any terminal phenoxy group indicating high conversion. The polymer showed glass transition at 278°C and very good thermal stability in synthetic air. GPC results indicate high molar mass development; Mw = 53200 and MWD = 2.29.

The effects of incorporation of heterocyclic moieties into fluorinated poly(ether imide) membranes on their gas transport properties were investigated. Four novel fluorinated poly(ether imide) (PEI) membranes were prepared from four different bis(ether amine)s namely, 4,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]biphenyl (BAQP); 1,4-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl] benzene (BATP); 2,6-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]pyridine (BAPy) and 2,5-bis[3′-trifluromethyl-4′(4′′-aminobenzoxy)bezyl]thiophene (BATh), and a fluorinated dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane (6FDA) as a common dianhydride. Gas transport properties of these membranes were measured to investigate the effect of chemical structure on gas permeation and diffusion processes over four different gases (e.g., CH4, N2, O2 and CO2) at different temperatures (e.g., 35, 45 and 55 °C) at an applied pressure of 3.5 bar. It has been found that at 35 °C the permselectivities of BAPy and BATh based polymeric membranes (6.4 and 6.6, respectively) toward O2 relative to N2 are higher in comparison to BAQP and BATP (5.5 and 5.3, respectively) containing PEI membranes. The permeability coefficient of CO2 for BAPy and BATh (51.92 and 45.31, respectively at 35 °C) based PEI membranes were observed to be much higher than BAQP and BATP based membranes (36.61 and 33.51, respectively at 35 °C) with comparable selectivity values of CO2 relative to CH4. All these membranes exhibit higher CO2/CH4 selectivity than those of common glassy polymers e.g., cellulose acetate, polysulfone and polycarbonate. The order of permeability of these gases was found as CO2 > O2 > N2 > CH4. The temperature dependency of permeation and diffusion processes enables to calculate the activation energies of the permeation and diffusion processes for these four different gases through four PEI membranes.

A series of new organosoluble and optically transparent poly(ether imide)s (PEIs) were synthesized by the polycondensation of trifluoromethyl substituted and phthalimidine cardo group based bis(ether amine), 3,3-bis-[4-{2′-trifluoromethyl 4′-(4″-aminophenyl)phenoxy}phenyl]-2-phenyl-2, 3-dihydro-isoindole-1-one with different fluorinated and non-fluorinated aromatic dianhydrides (2a–e). All the PEIs were well characterized by elemental analysis, NMR, FTIR spectroscopy, and gel permeation chromatography (GPC). The synthesized PEIs showed moderate to high inherent viscosity 0.41–0.61 dL/g and excellent solubility at room temperature in different organic solvents. All the transparent yellow films showed cut-off length upto 425 nm. They exhibited high tensile strengths upto 98 MPa, excellent thermostability upto 554°C for 5% weight loss, high glass transition temperature upto 327°C, and water uptake value less than 0.6%. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Four new poly(arylene ether)s have been prepared by the reaction of N-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PA) with four different perfluoroalkylated monomers namely 1,3-bis(4′-fluoro-3′-trifluoromethyl benzyl) benzene, 4,4′-bis(4′-fluoro-3′-trifluoromethyl benzyl) biphenyl, 2,6-bis(4′-fluoro-3′-trifluoromethyl benzyl) pyridine, and 2,5-bis(4′-fluoro-3′-trifluoromethyl benzyl) thiophene. The poly(arylene ether)s were characterized by different spectroscopic, thermal, mechanical, and electrical techniques. The poly(arylene ether) containing quadriphenyl unit in the main chain showed very high glass transition temperature of 291°C and outstanding thermal stability upto 556°C for 10% weight loss under a 4:1 nitrogen:oxygen mixture. The polymers were soluble in a wide range of organic solvents. Transparent thin films of these polymers exhibited tensile strengths upto 75 MPa and elongation at break upto 32%. The films of these polymers showed low water absorption of 0.26%. Copyright © 2009 John Wiley & Sons, Ltd.

A new indane containing unsymmetrical diamine monomer (3) was synthesized. This diamine monomer leads to a number of novel semifluorinated poly (ether imide)s when reacted with different commercially available dianhydrides like benzene-1,2,4,5-tetracarboxylic dianhydride (PMDA), benzophenone-3,3', 4,4'-tetracarboxylic dianhydride (BTDA), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 4,4'-oxydiphthalic anhydride (ODPA), and 4,4'-(4,4'-Isopropylidenediphenoxy)bis(phthalic anhydride) (BPADA) by thermal imidization route. All the poly(ether imide)s showed excellent solubility in several organic solvents such as N-methylpyrrolidone (NMP), N, N-dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), tetrahydrofuran (THF), chloroform (CHCl 3 ) and dichloromethane (DCM) at room temperature. These light yellow poly (ether imide)s showed very low water absorption (0.19―0.30%) and very good optical transparency. Wide angle X-ray diffraction measurements revealed that these polymers were amorphous in nature. The polymers exhibited high thermal stability up to 526°C in nitrogen with 5% weight loss, and high glass transition temperature up to 265°C. The polymers exhibited high tensile strength up to 85 MPa, modulus up to 2.5 GPa and elongation at break up to 38%, depending on the exact polymer structure.

Five new poly(arylene ether)s containing phthalimidine group in the main chain and pendent trifluoromethyl group have been prepared by the reaction of 4,4′-(bis-4-fluoro-3-trifluoromethylphenyl)benzene (BTF) with bisphenols. Different molar ratios of N-phenyl-3,3-bis(4-hydroxyphenyl)phthalimidine (PA) and 4,4′-isopropylidenediphenol (BPA) have been used to generate different copolymers. The polymers obtained by step growth polymerization exhibited weight-average molecular weight upto 134,000 g/mol with a polydispersity index of 2.1–2.4. The homopolymer from BTF and PA showed very high glass transition temperature of 258°C and outstanding thermal stability upto 536°C for 5% weight loss under nitrogen. The polymers were soluble in a wide range of organic solvents. Transparent thin films of these polymers exhibited tensile strengths upto 65 MPa and elongation at break upto 45% depending on the exact repeat unit structures. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Two new semifluorinated aromatic copoly(ether amide)s have been synthesized by direct polycondensation reaction of 5-t-butyl isophthalic acid (TIPA) with two different aromatic diamines; bis-2,2-[4-{2′-trifluoromethyl-4′-(4″-aminophenyl) phenoxy}phenyl]isopropylidene (BTAPPI) and bis-9,9-[4-{2′-trifluoromethyl-4′-(4″-aminophenyl)phenoxy}phenyl]fluorenylidene (BTAPPF) and, 4,4′-oxydianiline (ODA) as a comonomer in all cases. These polymers showed very good solubility in organic solvents like DMF, DMAc, NMP and pyridine. The polymers showed very good thermal stabilities, the temperature for 10% wt loss in nitrogen and air were upto 422°C and 412°C, respectively. The copoly(ether amide)s synthesized exhibited glass transition temperature (Tg) 248 (BTAPPI-ODA-TIPA) and 263°C (BTAPPF-ODA-TIPA). DMA analysis showed very good retention of storage modulus of the polymer up to Tg. The copoly(ether amide) films were flexible with tensile strength up to 91 MPa, elongation at break up to 15% and modulus of elasticity...

This mini-review summarizes the latest accomplishments with group 6 metal alkylidene-N-heterocyclic carbene complexes (metal = Mo, W) for use in olefin metathesis. Both the fundamentals and the unique features of this novel class of olefin metathesis catalysts are presented. Also, their use and performance in ring-closing metathesis, cross metathesis, homometathesis, and self-metathesis reactions as well as in ring-opening metathesis polymerization and cyclopolymerization is outlined.

A new organosoluble benzotrifluoromethyl group containing poly(p-phenylenevinylene) (BTFM-PPV) has been synthesized via Gilch polymerization. The polymer is soluble in common organic solvents such as tetrahydrofuran, chloroform, dichloromethane, toluene, and xylene. BTFM-PPV exhibited fluorescence emission peak with a very high blue shift at 474 nm with an excitation wavelength at 420 nm compared with many other PPV derivatives reported earlier. Incorporation of fluorated bezotrifluoromethyl pendent group in the PPV backbone lowers the HOMO and LUMO energy levels of BTFM-PPV (2.48 eV) which retarded the hole injection and increase the electron injection in the device. The current–voltage (I–V) characteristic of the polymer was measured by fabricating the polymer as ITO/BTFM-PPV/Al diode. The device performance was markedly improved by incorporation of 4-fluoro-3trifluoromethylphenyl units into the polymer main chain. The turn on voltage of the device observed from the I–V measurements was 7 V. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

This article describes the preparation of a series of processable fluorinated poly(ether imide)s from a new diamine monomer 4,9-bis-[4-(4′-amino-3-trifluoromethyl-biphenyl-4-yloxy)-phenyl]-2-phenyl-benzo[f]-isoindole-1,3-dione. The polymers showed extremely high Tg (up to 335 °C), outstanding thermal stability (up to 559 °C) and high tensile strength (up to 102 MPa). The transparent (λcut-off ≥ 363 nm) membranes from these polymers were investigated for their gas transport properties for CO2, O2, N2 and CH4 at three different temperatures. The effect of the benzo[f]isoindole-1,3-dione moiety and the aromatic dianhydrides (BPADA, 6FDA, BTDA, ODPA and PMDA) towards the glass transition temperatures of the polymers and their consequences on gas transport properties have been investigated. The polymer prepared from 6FDA showed the highest permeability coefficient for all the gases (PCO2 = 71.3, PO2 = 25.4) whereas BPADA based polymer exhibited the highest permselectivity (CO2/CH4 ∼ 37.2 and O2/N2 ∼ 8.4), staying closer to the latest upper boundary limit drawn by L. M. Robeson.