Norbornene Dicarboximide Research Articles

Synthesis, characterization, and optical properties of ROMP copolymers with pendant carbazole and coumarin groups

Two series of random copolymers containing at the same time two fluorescent groups, carbazole and coumarin, linked to a poly(norbornene dicarboximide) backbone have been prepared by controlled ring-opening metathesis polymerization (ROMP), promoted by Grubbs’ third generation catalyst (G3). The relative amount of the two functionalities was systematically varied along the copolymer chain, and the high degree of structural control observed allowed also for the preparation of a block copolymer with an equimolar content of fluorophore groups.In comparison to the related homopolymers, all the random copolymers exhibited in solution typical photoluminescence due to the carbazole or coumarin moiety, together with fluorescence arising from the energy transfer from the donor carbazole groups to the acceptor coumarin groups. This energy transfer seems to occur through intramolecular interactions, as it is not observed in the block copolymer and in the 50/50 homopolymer blend. On the other hand, in the solid state also the energy transfer from carbazole to coumarin through interchain interactions can take place. Of note, moving from solution to solid state fluorescence analysis, a blue shift of the band related to the energy transfer phenomenon is observed. This finding could be related to a combined effect of energy and electron transfer from donor to acceptor.

Synthesis and Characterization of Thiol-Functionalized Polynorbornene Dicarboximides for Heavy Metal Adsorption from Aqueous Solution.

The contamination of water resources with heavy metals is a very serious concern that demands prompt and effective attention due to the serious health risks caused by these contaminants. The synthesis and ring-opening metathesis polymerization (ROMP) of norbornene dicarboximides bearing thiol pendant groups, specifically, N-4-thiophenyl-exo-norbornene-5,6-dicarboximide (1a), N-4-(methylthio)phenyl-exo-norbornene-5,6-dicarboximide (1b) and N-4-(trifluoromethylthio)phenyl-exo-norbornene-5,6-dicarboximide (1c), as well as their assessment for the removal of heavy metals from aqueous systems, is addressed in this work. The polymers were characterized by NMR, SEM and TGA, among others. Single and multicomponent aqueous solutions of Pb2+, Cd2+ and Ni2+ were employed to perform both kinetic and isothermal adsorption studies taking into account several experimental parameters, for instance, the initial metal concentration, the contact time and the mass of the polymer. In general, the adsorption kinetic data fit the pseudo-second-order model more efficiently, while the adsorption isotherms fit the Freundlich and Langmuir models. The maximum metal uptakes were 53.7 mg/g for Pb2+, 43.8 mg/g for Cd2+ and 29.1 mg/g for Ni2+ in the SH-bearing polymer 2a, 46.4 mg/g for Pb2+, 32.9 mg/g for Cd2+ and 27.1 mg/g for Ni2+ in the SCH3-bearing polymer 2b and 40.3 mg/g for Pb2+, 35.9 mg/g for Cd2+ and 27.8 mg/g for Ni2+ in the SCF3-bearing polymer 2c, correspondingly. The better performance of polymer 2a for the metal uptake was ascribed to the lower steric hindrance and higher hydrophilicity imparted by –SH groups to the polymer. The results show that these thiol-functionalized polymers are effective adsorbents of heavy metal ions from aqueous media.

ROMP of norbornene and oxanorbornene derivatives with pendant fluorophore carbazole and coumarin groups

A series of new (oxa)norbornene dicarboximide monomers, decorated with carbazole and coumarin as pendant fluorophore groups, were synthesized and characterized. Their behaviour in ring-opening metathesis polymerization (ROMP) was explored in the presence of commercial Grubbs’ third generation catalyst G3 and cis-selective catalyst GZ. Norbornene dicarboximide (NDI) monomers were successfully polymerized by both the catalysts, while oxanorbornene dicarboximide (ONDI) analogues showed scarce reactivity toward polymerization promoted by GZ. The nature of the spacer (ethylene or p-xylene) between the NDI unit and the chromophore seems to not affect the outcome of the polymerization. Moving from G3 to GZ, it was possible to synthetize NDI-based polymers with cis-olefin content increasing from 47 to 89%, depending on the nature of the pendant fluorophore group. The obtained polymers showed photoluminescence in solution and solid state owing to the carbazole or coumarin fragment, regardless of the nature of the spacer and cis-olefin amount. Interestingly, a significant excimer emission due to the overlap of carbazole groups was observed for a carbazole-functionalized polymer film, as a result of the combined effect of two factors, the stiffness of the spacer (p-xylene) linking the NDI moiety to the fluorophore and the high stereoregularity degree (83% cis) of the main chain.

Synthesis, characterization, and assessment of novel sulfonated polynorbornene dicarboximides as adsorbents for the removal of heavy metals from water.

The occurrence of heavy metals in the natural aquatic systems arising from anthropogenic sources is an issue of global and environmental concern because of their extremely harmful effects to living beings even in rather low concentrations. The synthesis and ring-opening metathesis polymerization (ROMP) of novel norbornene dicarboximides bearing highly aromatic pendant groups, specifically, N-4-tritylphenyl-norbornene-5,6-dicarboximide (2a) and N-2,4,6-(triphenyl)phenyl-norbornene-5,6-dicarboximide (2b), their hydrogenation and further polymer sulfonation to render them adsorbents for the uptake of heavy metal ions from water is reported in this study. The macromolecules were characterized by means of FT-IR, 1H NMR, and thermal analysis, among others. A thoroughly kinetic and isothermal study of adsorption in single and ternary aqueous solutions of Pb2+, Cd2+, and Ni2+ was performed considering several experimental variables for instance initial metal concentration, contact time and solution pH. In general, the experimental data were adjusted more efficiently to the pseudo-second order kinetic model and to the Freundlich isotherm model, respectively. The maximum removal amounts were found to be 55.7 mg/g for Pb2+, 33.9 mg/g for Cd2+, and 10.2 mg/g for Ni2+ in the sulfonated trityl-bearing polymer 5a while those found for the sulfonated triphenyl-bearing polymer 5b were 31.5 mg/g for Pb2+, 26.6 mg/g for Cd2+, and 7.0 mg/g for Ni2+, respectively. The higher heavy metal removal capacity of polymer 5a was attributed to its also higher degree of sulfonation. The outcomes indicate that these novel sulfonic acid containing polymer-based adsorbents are effective for the uptake of heavy metallic elements from water.

Synthesis and Ring-Opening Metathesis Polymerization of a New Norbornene Dicarboximide with a Pendant Carbazole Moiety

A new norbornene dicarboximide presenting a pendant carbazole moiety linked by a p-methylene benzyl spacer is synthesized. This carbazole-functionalized monomer is polymerized via ring-opening metathesis polymerization using Grubbs third-generation catalyst. Microstructural analysis of resulting polymers performed by Nuclear Magnetic Resonance (NMR) shows that they are stereoirregular. Wide-angle X-ray diffraction (WAXD) and thermal (DSC) analysis indicate that polymers are also amorphous. With respect to the fluorescence analysis, both solution and film polymer samples exhibit only “normal structured” carbazole fluorescence, while excimer formation by overlap of carbazole groups is not detected.

Synthesis and Gas Permeability of Chemically Cross‐Linked Polynorbornene Dicarboximides Bearing Fluorinated Moieties

AbstractThis work reports on the synthesis of a novel bifunctional norbornene dicarboximide monomer (HFDA) based on 4,4′‐(hexafluoroisopropylidene)bis(p‐phenyleneoxy)dianiline and its application as a cross‐linking agent in the ring‐opening metathesis polymerization (ROMP) with N‐3‐trifluoromethylphenyl‐exo,endo‐norbornene‐5,6‐dicarboximide (mCF3) employing the Grubbs 2nd generation catalyst (I) and cis‐1,4‐diacetoxy‐2‐butene as a chain transfer agent (CTA) to yield a series of soluble nonlinear highly branched chains polymers with increasing degree of cross‐linking. A comparative study of gas transport in membranes based on these cross‐linked polynorbornene dicarboximides is performed and the gases studied are hydrogen, oxygen, nitrogen, carbon dioxide, methane, ethylene, and propylene. It is found that cross‐linking increases the gas permeability, leads to the highest separation factor reported to date for the H2/C3H6 mixture in this kind of polymers, and also enhances the CO2 plasticization resistance up to 14 atm upstream pressure. The chemical cross‐linking approach employed in this research is an effective tool to enhance gas transport properties for dense polynorbornene dicarboximide membranes.

Efficient Two Step Synthesis for Trimethylsiloxy-Functionalized New Polymers

We have presented an efficient strategy for the synthesis of trimethylsiloxy end-functionalized new polymers using ring-opening metathesis polymerization with ruthenium initiator, [(PCy3)2Cl2Ru=CHPh]. The key steps for the new silicon containing end-capped polymers are: In the first step, direct end-capping is carried out by adding cis-2-butene-1,4-diol to the ring-opened norbornene dicarboximides. In the second step, the reaction of hydroxy-functionalized polymers with trimethylsilyl chloride gives trimethylsiloxy-functionalized polymers. The best results for the end group introduction are achieved by reacting the living chains with an excess of the terminating agent. The molecular and structural features of the obtained polymers were confirmed by NMR and GPC analyzes, and their thermal properties were investigated by DSC. End-functionalization efficiency values were determined by NMR spectroscopy.

Synthesis and gas transport properties of new polynorbornene dicarboximides bearing trifluoromethyl isomer moieties

This work reports on the synthesis and ring-opening metathesis polymerization (ROMP) of new structural isomers based on norbornene dicarboximides bearing trifluoromethyl moieties, specifically, N-2-trifluoromethylphenyl- exo- endo-norbornene-5,6-dicarboximide (2a) and N-3-trifluoromethylphenyl- exo- endo-norbornene-5,6-dicarboximide (2b) using tricyclohexylphosphine [1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene] ruthenium dichloride (I), bis(tricyclohexylphosphine) benzylidene ruthenium (IV) dichloride (II), and bis(tricyclohexylphosphine) p-fluorophenylvinylidene ruthenium (II) dichloride (III). It is observed that the –CF3 moiety attached to the ortho position of the aromatic ring increases the thermal and mechanical properties of the polymer, whereas the meta substitution has the opposite effect. A comparative study of gas transport in membranes based on these fluorinated polynorbornenes showed that the –CF3 ortho substitution increases the permeability of the polymer membrane as a consequence of the increase of both the gas solubility and the gas diffusion. In contrast, the gas permeability coefficients of the meta-substituted polymer membrane are rather similar to those of the non-fluorinated one attributed to a lower fractional free volume. The meta-substituted polymer membrane besides showing the largest permselectivity coefficients of all the isomers studied here was also found to have one of the largest permselectivity coefficients reported to date for separating hydrogen/propylene in glassy polynorbornene dicarboximides.

An autonomous self-healing system based on ROMP of norbornene dicarboximide monomers

This work reports the first example of an autonomous self-healing process at ambient temperature based on the ROMP of mono- and di-functional norbornene dicarboximides. The mixture of the mono- and di-functional norbornene dicarboximide monomers was successfully encapsulated by a method involving urea-formaldehyde and used as healing agents. All specimens were prepared by mixing microcapsules (10 wt%) Grubbs' ruthenium initiators RuCl2(=CHPh)(PCy3)2 (G1) (5 mol%) or RuCl2(=CHPh)(PCy3)(IMesH2) (G2) (2.5 mol%) with the epoxy resin components. Fracture tests were carried out at ambient temperature on all specimens using the compact tension geometry in order to determine a value for the critical stress intensity factor, KIC. The percentage of healing was calculated as the ratio of KIC after healing to that of the virgin test. It was found that while the specimens containing healing agent of high viscosity comprising of just a mixture of mono- and di-functional norbornene dicarboximide monomers required clamping to initiate healing, those containing healing agent of low viscosity comprising a mixture of these two monomers and 25 wt% of ethylidene norbornene, as a reactive diluent monomer, healed unclamped. The healing efficiency of 33% was observed and this developed between 11 and 24 h.

Synthesis and ionic transport of sulfonated ring-opened polynorbornene based copolymers

The N-pentafluorophenyl-exo-endo-norbornene-5,6-dicarboximide (1a) and N-phenyl-exo-endo-norbornene-5,6-dicarboximide (1b) monomers were synthesized and copolymerized via ring opening metathesis polymerization (ROMP) using bis(tricyclohexylphosphine)benzylidene ruthenium(IV) dichloride (I) and tricyclohexylphosphine[1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene][benzylidene]ruthenium dichloride (II). Experiments, at distinct monomer molar ratios, were carried out using catalyst I in order to determine the copolymerization reactivity constants by applying the Mayo-Lewis and Fineman-Ross methods. Moreover, both catalysts were used to produce random and block high molecular weight copolymers of 1a with 1b and 1a with norbornene (NB) which were further hydrogenated using a Wilkinson’s catalyst. Then, the saturated copolymers underwent a nucleophilic aromatic substitution by reacting with sodium 4-hydroxybenzenesulfonate dihydrate to generate new polynorbornene ionomers bearing fluorinated pendant benzenesulfonate groups. A thorough study on the electrochemical characteristics involving electromotive forces of concentration cells and proton conductivity of cation-exchange membranes based on a block copolymer of norbornene dicarboximides containing structural units with phenyl and fluorinated pendant benzenesulfonate moieties is reported. The study of electromotive forces (emf) of concentration cells with the sulfonated membrane of copolymer 8 separating electrolyte solutions of different concentration indicate that the membranes exhibit high permselectivity to protons and sodium ions at moderately low concentrations. In principle, these results suggest that the membranes can be considered candidates for ionic separation applications.

Synthesis of Novel Pyridinium Betaine Precursors from exo-Norbornene Dicarboximides

N-heterocyclic norbornene Dicarboximides were synthesized by reacting the exo-norbornene-5,6-dicarboxylic anhydride with 2-, 3-, and 4-aminopyridine. The amides resulting from 3 and 4-aminopyridine derivatives were converted into the corresponding betaines via Menshutkin reaction using ethyl-bromoacetate. The chemical structures of the obtained products were confirmed by FT-IR and 1H and 13C NMR spectroscopy, EA and MS as well as by calculation of 1H and 13C NMR chemical shifts using the GIAO method (PW91/6-311G++ (3df, 3pd) approximation by GAUSSIAN and PW91/IGLO-III approximation by deMon2k).

Latent ruthenium initiators containing fluoro aryloxide ligands

A new ligand, methyl 2,3,5,6-tetrafluoro-4-oxybenzoate (C 8H 3F 4O 3), combining an electron withdrawing group (C 6F 4) to tune the reactivity with an anchor group (CO 2Me) for immobilization on supports, was used to prepare four new ruthenium initiators, viz. Ru(C 8H 3F 4O 3) 2( CHPh)(3-Br–C 5H 5N)(H 2IMes) and Ru(C 8H 3F 4O 3) 2XL, where X = C,N-( CHCH 2CH 2-2-C 5H 4N) and L = P i Pr 3, PCy 3 or H 2IMes. The new ligand greatly reduced the reactivity of the ruthenium centre at room temperature. The 1H NMR and DSC investigation for the ROMP of norbornene dicarboximide monomers clearly demonstrated that the Ru(C 8H 3F 4O 3) 2XL initiators were inactive at room temperature and required elevated temperatures for their activation.

Thermosetting ROMP materials with thermally degradable linkages

Mono- and di-functional norbornene dicarboximide monomers containing acetal ester groups were synthesised. The ROMP of the di-functional monomer using Grubbs ruthenium first generation initiator at ambient temperature produced crosslinked material. Materials with various crosslink densities were prepared by the ROMP, under the same condition, of mixtures of the mono- and di-functional monomers. The FT-IR spectra clearly showed the presence of an acetal C–O band at 1135 cm−1. The TGA study of the crosslinked materials showed that they are stable to 150 °C and that they exhibit rapid breakdown at about 200 °C, as the result of the thermal decomposition of the acetal ester linkage. FT-IR analysis of the retrieved materials following TGA-MS showed that the intensity of acetal C–O band at 1135 cm−1 was greatly reduced.

Homogeneous catalysis in the preparation of new carboximide-based thermoplastic polymers

The ring opening metathesis polymerization (ROMP) of norbornene dicarboximide derivatives 3( a– c) bearing halo-substituted phenyl groups was carried out with well-defined organometallic catalyst (PCy 3) 2(Cl) 2Ru CHPh. This catalyst is highly active for the polymerization of norbornene dicarboximide derivatives. Exo-N-4-chlorophenyl-norbornene-5,6-dicarboximide (ClPhNDI, 3a), exo-N-4-bromophenyl-norbornene-5,6-dicarboximide (BrPhNDI, 3b), exo-N-4-iodophenyl-norbornene-5,6-dicarboximide (IPhNDI, 3c) monomers gave high molecular weight thermoplastic polymers in high yields (77–96%). All of the prepared polymers were soluble in common organic solvents at room temperature and gave similar IR and NMR spectra. Their glass transition temperatures were detected at temperatures over 187 °C. The surface properties of ROMP polymers were investigated by SEM.

Halogenated Olefins as Chain Transfer Agents in the Synthesis of Telechelic Polynorbornenes Using Ruthenium Alkylidene Catalysts. Computational and Experimental Studies

Ring-opening metathesis polymerization (ROMP) of norbornene (NB) and its derivatives N-adamantyl-exo- endo-norbornene-5,6-dicarboximide (AdNDI) and N-cyclohexyl-exo-endo-norbornene-5,6-dicarboximide (CyNDI) in the presence of cis-1,4-dichloro-2-butene (2a) and cis-1,2-dichloro-ethylene (2b) as chain transfer agents (CTAs) using a (1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazolilydene) (PCy3)Cl2Ru=CHPh (I) has been studied. � Halogenated ole- fin 2b shows no activity as a CTA whenhalogenated olefin 2a is readily cross-metathesized with NB and norbornene dicarboximides. The chain transfer reaction pathways during the ROMP of NB to 2b using a (1,3-diphenyl-4,5- dihydroimidazol-2-ylidene) (PCy3)Cl2Ru=CHPh (1) have been studied at B3LYP/LACVP* level of theory. The calcula- tions show that 2b is a poor substrate for the metathesis reaction due to the steric effect produced by chlorine atoms di- rectly linked to the double bond. The calculated Gibbs free activation energy of a chain transfer reaction from ring-opened NB to 2b was 25.1 kcal/mol.

Synthesis and Ring‐Opening Metathesis Polymerization of New Oxanorbornene Dicarboximides with Fluorine Pendant Groups

AbstractThe synthesis of exo‐N‐3,5‐bis(trifluoromethyl)phenyl‐7‐oxanorbornene‐5,6‐dicarboximide (TFMPhONDI, 2a), exo‐N‐4‐fluorophenyl‐7‐oxanorbornene‐5,6‐dicarboximide (FPhONDI, 2b), and exo‐N‐pentafluorophenyl‐7‐oxanorbornene‐5,6‐dicarboximide (PFPhONDI, 2c) monomers is described. Poly(norbornene dicarboximide)s were obtained via ROMP using bis(tricyclohexylphosphine)benzylidine ruthenium(IV) dichloride (I) and tricyclohexylphosphine [1,3‐bis(2,4,6‐trimethylphenyl)‐4,5‐dihydroimidazolilydene][benzylidene] ruthenium dichloride (II). Poly‐TFMPhONDI (3a) bearing a trifluoromethylaryl moiety showed a higher Tg and improved mechanical properties as compared to poly‐FPhONDI (3b) and poly‐PFPhONDI (3c).magnified image