Norbornene Monomers Research Articles

Thermally Curable Polyoxanorbornene by Ring Opening Metathesis Polymerization

AbstractA novel norbornene monomer bearing a thermally curable benzoxazine group is synthesized and polymerized by ROMP using the Grubbs first‐generation ruthenium catalyst. The $\overline {M} _{{\rm w}} $ of the side‐chain benzoxazine functionalized polyoxanorbornene can be up to 87 000 Da with unimodal molecular‐weight distribution and narrow polydispersity between 1.18 and 1.65. Thermally activated ring‐opening polymerization of benzoxazine moieties leads to the formation of highly cross‐linked structures. The effects of molecular weight on the thermal ROP of polybenzoxazine precursors are examined.magnified image

Synthesis of complex architectures of comb block copolymers

The synthesis of comb block copolymers by ring opening metathesis polymerization (ROMP), ring opening polymerization (ROP), and atom transfer radical polymerization (ATRP) is described. Block copolymers were synthesized by the ROMP of oxanorbornene and norbornene monomers followed by hydrogenation of the olefins along the backbone. One block of these diblock copolymers possessed initiators either for the ROP of (3 S)- cis-3,6-dimethyl-1,4-dioxane-2,5-dione or the ATRP of butyl acrylate. The synthesis and characterization of comb polymers with arms composed of poly(lactic acid) and poly(butyl acrylate) are described. These polymers had well-defined peaks in the size exclusion chromatography spectra which indicated that no homopolymers were synthesized. A comb block copolymer with polymeric arms of poly(styrene- b-vinylpyridine) is described. Vinylpyridine was polymerized from a comb polymer with poly(styrene) arms by ATRP at high dilution of the comb polymer.

Stable crosslinked vinyl‐addition‐type polynorbornene graft copolymer proton‐exchange membranes

AbstractThe graft copolymer poly(butoxymethylene norbornene‐co‐norbornenemethylene bromoisobutyrylate) [P(BN/NB)]‐graft‐poly(hydroxyethyl methacrylate) (PHEMA) was synthesized by the atom transfer radical polymerization of 2‐hydroxyethyl methacrylate from a copolymer prepared by two functional norbornene monomers via a vinyl addition mechanism. The graft copolymer P(BN/NB)‐g‐PHEMA was further crosslinked with 4,5‐imidazole dicarboxylic acid (IDA) and then doped with phosphoric acid (H3PO4) to form imidazole–H3PO4 complexes. The results show that the polynorbornene backbone and crosslinked micromorphology produced low methanol permeability in the membranes (from 1.5 × 10−7 to 3.8 × 10−6 cm2/s) and endowed the membranes with good mechanical properties (with elastic modulus values of 692.7 to 159.7 MPa, elongation at break values from 2.7 to 22.7%, and tensile strength at break values from 14.4 to 5.5 MPa) and excellent thermal stability (up to 280°C). Furthermore, the proton conductivities of the membranes increased with increasing temperature and increasing content of IDA/H3PO4 in the membranes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synthesis of reactive poly(norbornene): Ring‐opening metathesis polymerization of norbornene monomer bearing cyclic dithiocarbonate moiety

AbstractA norbornene monomer bearing cyclic dithiocarbonate moiety (NB‐DTC) was successfully synthesized from the corresponding precursor having epoxy moiety by its reaction with carbon disulfide. NB‐DTC underwent the ring‐opening metathesis polymerization (ROMP) catalyzed by a ruthenium carbene complex to give the corresponding poly(norbornene). The dithiocarbonate moiety incorporated into the side chain of the obtained poly(norbornene) reacted with amine to afford the corresponding thiourethane moiety with thiol group, which underwent oxidative S‐S coupling and/or addition reaction to the C‐C double bond in the main chain, leading to formation of a cross‐linked polymer. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.

Vinyl-type polynorbornene with 9,9′-(1,1′-biphenyl)-4,4′-diylbis-9H-carbazole side groups as a host material for highly efficient green phosphorescent organic light-emitting diodes

The soluble polynorbornene (P1) bearing 9,9′-(1,1′-biphenyl)-4,4′-diylbis-9H-carbazole (CBP) side groups was investigated as a host material for green emitters in phosphorescent OLED devices. The vinyl addition polymerization of norbornene monomers using Pd(II) catalyst efficiently produces P1 in combination with 1-octene chain transfer agent. P1 exhibits high thermal stability with high decomposition (Td5 > 451 °C) and glass transition temperatures (Tg > 361 °C). The HOMO (ca. −5.5 eV) and LUMO (ca. −2.1 eV) levels with the triplet energy of ca. 2.60 eV suggest that P1 is suitable for a host material for green emitters. The solution-processed devices based on the emissive layers containing P1host doped with various concentration of fac-Ir(ppy)3 (1–6 wt%) display stable green emission of fac-Ir(ppy)3 with high device performances. The external quantum efficiency and power efficiency reach 7.2% and 11 lm/W, respectively, at the optimum doping concentration of fac-Ir(ppy)3 (2 wt%). The device performances are found to be slightly lower than those of PhOLED with molecular CBP host but higher than those of a PVK-based device. It is shown that in conjunction with the good processability of polynorbornene backbones, the high levels of the effective hole and electron mobilities of P1 (ca. 10−3 and 10−5 cm2/Vs, respectively) as well as large triplet energy inherited from CBP side groups are mainly responsible for the high performance of the phosphorescent OLEDs with solution-processed P1host:emitter layers.

Hydrogels Based on Living Ring-Opening Metathesis Polymerization

Living ring-opening metathesis polymerization (ROMP) of a hydrophilic norbornene monomer (M4) was performed successfully in air at room temperature using Grubbs’ third generation (G3) catalyst as the initiator. ROMP was then used to copolymerize M4 with a hydrophilic difunctional norbornene cross-linker to develop a rapid and efficient method for preparing hydrogels. Although intramolecular cyclization was observed under dilute conditions, the critical gelation behavior was found to agree with the mean-field theory of Flory and Stockmayer (FS theory) more consistently than that of conventional free radical polymerization systems. By changing the length of the primary polymer chains, the initial molar ratio between monomer and cross-linker, and the length of the cross-linker, the equilibrium swelling ratio and the corresponding mechanical properties of the resultant hydrogels were manipulated across a broad range.

Ketene Functionalized Polyethylene: Control of Cross-Link Density and Material Properties

The functionalization and cross-linking of polyethylene is synthetically challenging, commonly relying on highly optimized radical based postpolymerization strategies. To address these difficulties, a norbornene monomer containing Meldrum's acid is shown to be effectively copolymerized with polyethylene using a nickel α-iminocarbaxamidato complex, providing high-melting, semicrystalline polymers with a tunable incorporation of the functional comonomer. Upon heating the copolymer to common polyethylene processing temperatures, the thermolysis of Meldrum's acid to ketene provides the desired reactive group. This simple and versatile methodology does not require small molecule radical sources or catalysts, and the dimerization of the in situ generated ketenes is shown to provide tunable cross-linking densities in polyethylene. Subsequent rheological and tensile experiments illustrate the ability to tune cross-linked polyethylene properties by comonomer incorporation and elucidate valuable structure/property relationships in these materials. This study illustrates the power of well-defined and synthetically accessible functional groups in polyolefin synthesis and functionalization.

Synthesis and hole-transporting properties of vinyl-type polynorbornenes with ethyl ester linked triarylamine side groups

Palladium(II)-catalyzed polymerization of norbornene monomers bearing triarylamine side groups was investigated to prepare the vinyl-type polynorbornenes having hole-transporting properties. Norbornene monomers ( M1– M3) with the ethyl ester linked aryldiphenylamines where the aryl group is phenyl, m-tolyl, and 1-naphthyl, respectively, were employed. The combined use of the Pd(II) catalyst supported by N-heterocyclic carbene ligand and AgSbF 6 leads to the production of soluble polynorbornenes ( P1– P3). While the cyclic voltammetry measurements show the relatively low oxidational stability of polymers, the polymers exhibit the high glass transition temperature of 305–333 °C. The atomic force microscopy images of the thin film of P1 reveal the very smooth film surface with a roughness of 0.29 nm, indicating the good film-forming capability of polymer. When incorporated as a hole-transporting layer in Alq 3-based electroluminescent devices, the spin-coated polymer films display hole-transporting property suitable for the proper green emission of Alq 3. Among the devices studied, the one based on 1-naphthylamine-containing P3 exhibits the highest performance in terms of luminance and external quantum efficiency.

Synthesis of a norbornene monomer having cyclic carbonate moiety based on CO2 fixation and its transition metal-catalyzed polymerizations

A norbornene monomer bearing cyclic carbonate moiety (NB-CC) was successfully synthesized from the corresponding precursor having epoxy moiety by its reaction with carbon dioxide under atmospheric pressure, which was efficiently catalyzed by lithium bromide. NB-CC underwent the ring-opening metathesis polymerization (ROMP) catalyzed by a ruthenium carbene complex to give the corresponding poly(norbornene), of which side chain inherited the cyclic carbonate moiety from the monomer without any deterioration. The same ROMP system was applicable to the copolymerization of NB-CC and 5-butyl-2-norbornene (BNB), which afforded the corresponding copolymer with a composition ratio same as a feed ratio. In addition, by using a catalytic system consisted of palladium (II) acetate/tricyclohexylphosphine/triphenylcarbenium tetrakis(pentafluorophenyl)borate, the copolymerization of NB-CC and BNC proceeded successfully in a vinyl addition polymerization mode to give the corresponding poly(norbornene) having CC moiety in the side chain. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3896–3902, 2010

Ring-opening metathesis polymerization of N-substituted-5-norbornene-2,3-dicarboximides in the presence of chiral additives

Chiral and achiral amine-functionalized norbornene monomers endo-/exo-N-(S)-(−)-α-methylbenzyl-5-norbornene-2,3-dicarboximide (endo-/exo-(S)-MBnNDI), endo-/exo-N-phenyl-5-norbornene-2,3-dicarboximide (endo-/exo-PhNDI) and endo-/exo-N-cyclohexyl-5-norbornene-2,3-dicarboximide (endo-/exo-CHNDI) were synthesized and polymerized using 1st Generation Grubbs Catalyst, and the chiroptical properties of these polymers were studied. Specific rotations of higher Mn poly(endo-(S)-MBnNDI)s were negatively large compared with those of lower Mn polymers. Using (−)-spartaine (Sp) as a chiral additive, some polymers exhibited stronger chiroptical properties compared with polymers that were obtained without the chiral additive. Chiral and achiral amine-functionalized norbornene monomers were synthesized and polymerized using 1st Grubbs Catalyst, and the chiroptical properties of the polymers were studied. The tendency to increase the absolute value of specific rotation with an increase in Mn was observed. Using (−)-spartaine (Sp) as a chiral additive, the chiroptical property of the obtained polymer was enhanced in some cases.

Development and characterization of lithium salts doped nanoconductive ROMP polymers

The work presented in this paper describes a new technique for the design and synthesis of nanoconductive polymers. These nanoconductive materials were based on the ROMP of norbornene monomers with oxygen in the 7-position using Grubbs ruthenium initiator, Ru( CHPh)(PCy 3) 2Cl 2, and mixing the resulting polymer with various inorganic salts such as LiBF 4, LiPF 6, LiAsF 6 and LiSbF 6. The norbornene derivative monomers and the corresponding ROMP polymers were fully characterized by spectral methods. The ROMP polymers containing inorganic salts were investigated by ESEM (environmental scanning electron microscopy) for the formation of nano-structures. The distribution of the lithium salts within the polymer matrix was determined by IBA analysis. The conductivity measurements were carried out on thin films of the ROMP polymers containing inorganic salts.

Ring-Opening Metathesis Block Copolymerization of Amino Acid Functionalized Norbornene Monomers. Effects of Solvent and pH on Micelle Formation

Amino acid derived norbornene monomers having unprotected carboxy (1) and amino groups (2) and 7-oxanorbornene having ester groups (3) were block copolymerized using the Grubbs ruthenium complexes. In the combination of 1 and 2, block copolymers with number-average molecular weights ranging from 43 000 to 95 000 were obtained in good yields. Poly(1)75-block-poly(2)25 was soluble in 0.5 M NaOH(aq) but insoluble in 0.1 M HCl, while poly(1)25-block-poly(2)75 was soluble in 0.1 M HCl but insoluble in 0.5 M NaOH(aq). Thus, the block compositions remarkably affected the solubility of the copolymers in acidic and basic media. On the other hand, poly(2)62-block-poly(3)38 was soluble in H2O but insoluble in CH2Cl2 and CHCl3, while poly(2)38-block-poly(3)62 was soluble in CH2Cl2 and CHCl3 but insoluble in H2O. In this monomer combination, the block compositions significantly affected the solubility of the copolymers in organic and aqueous media. 1H NMR spectroscopic, turbidity, and dynamic light scattering measurements revealed that poly(1)50-block-poly(2)50 formed micelles with a diameter around 130 nm in 0.5 M NaOH(aq). In a similar manner, it was revealed that poly(2)62-block-poly(3)38 and poly(2)38-block-poly(3)62 formed micelles with a diameter around 80 nm in H2O and reverse micelles with a diameter around 45 nm in CH2Cl2, respectively.

Palladium(ii) complexes with pentafluorophenyl ligands: structures, C6F5 fluxionality by 2D-NMR studies and pre-catalysts for the vinyl addition polymerization of norbornene

The palladium(II) complex [Pd(C(6)F(5))Cl(bpzm*)] (5) [bpzm* = bis(3,5-dimethylpyrazol-1-yl)methane] was characterized by (1)H,(1)H-TOCSY, (1)H-NOE difference spectra, (1)H,(19)F-HOESY and (13)C,(1)H-HMBC 2D-NMR techniques. Chemical exchange of the methylene protons from (1)H,(1)H-NOESY cross peaks and exchange of the ortho- and meta-fluorine atoms, respectively, from (19)F,(19)F-EXSY cross peaks indicates that the Pd-bpzm* chelate ring boat-to-boat inversion occurs at a rate slower than the NMR time scale together with a concomitant change of the C(6)F(5) atom positions. The presence of three (19)F-NMR signals for 2F(o) : 1F(p) : 2F(m) of the C(6)F(5) ligand for complexes [Pd(C(6)F(5))Cl(tmeda)] (1) and [Pd(C(6)F(5))Cl(bipy)] (3) (tmeda = N,N,N',N'-tetramethylethylenediamine; bipy = 2,2'-bipyridine) is interpreted as being due to identical hemi-spaces above and below an apparent symmetry plane coinciding with the Pd-coordination plane instead of free ring rotation. The molecular structures of 1, 3 and 5 from single-crystal studies suggest that the hindered C(6)F(5) rotation is not limited to 5 but is also present in 1 and 3 due to ligand repulsion. Complexes [Pd(C(6)F(5))Cl(tmeda)] (1), [Pd(C(6)F(5))OH(tmeda)] (2), [Pd(C(6)F(5))Cl(bipy)] (3), [Pd(C(6)F(5))OH(bipy)] (4) and [Pd(C(6)F(5))Cl(bpzm*)] (5) have been applied as pre-catalysts for the vinyl homopolymerization of norbornene in combination with the cocatalyst methylaluminoxane (MAO). Activities of more than 10(6) g(polymer)/(mol(Pd) h) could be reached with these catalytic systems. Based on the spectrochemical series, pre-catalysts 1 and 2 with the pure sigma-donor and more weakly bound aliphatic amine ligands showed higher polymerization activities than compounds 3-5 with modest pi-accepting and stronger bound aromatic substituents. This is reasoned with a kinetic activation effect through a faster removal of the more weakly bound ligands upon reaction with MAO together with the chloro or hydroxo ligands to give the active, almost "naked" Pd(2+) cations. For the activation mechanism, (1)H-, (13)C- and (19)F-NMR studies of the MAO activated complex 5 showed about 13% chlorine-to-methyl exchange for a molar Pd : Al ratio of 1 : 10. For 5 : MAO at a Pd : Al ratio of 1 : 100 abstraction of C(6)F(5) takes place with a redox reaction giving Pd metal and C(6)F(5)-CH(3) in the absence of norbornene monomer.

Monitoring Block-Copolymer Crossover-Chemistry in ROMP: Catalyst Evaluation via Mass-Spectrometry (MALDI)

We report on the monitoring and evaluation of the crossover reaction in ring-opening metathesis polymerization (ROMP) via MALDI methods. ROMP of various monomers using several catalytic systems (first-generation (I) and third-generation Grubbs-type (III)) was investigated with structurally different norbornene monomers derived from (±)endo,exo-bicyclo[2,2,1]-hept-5-ene-2,3-dicarboxylic acid-bis-O-methyl ester (monomer A), (±)endo,exo-bicyclo[2,2,1]-hept-5-ene-2,3-dicarboxylic acid-bis-O-2,2,6,6-tetramethyl piperidinoxyl-ester (monomer T), (±)exo-N-(4,4,5,5,6,6,7,7,7-nonafluoroheptyl)-10-oxa-4-azatricyclodec-8-ene-3,5-dione (monomer D), and the highly strained monomer 2-methyl-2-phenyl-cyclopropene (monomer E). The crossover reactions as well as the polymerization kinetics of the various monomers were studied in detail, in particular, using matrix-assisted laser desorption ionization mass spectrometry (MALDI). Catalyst III offered access to the synthesis of highly defined block copolymers, generating poly(A-b-T), poly(A-b-D), and poly(A-b-E) diblockcopolymers in high precision, whereas catalyst I offered access to the diblockcopolymers poly(A-b-D) and poly(A-b-E). Poly(A) was used as a probe to analyze the crossover reaction, revealing well-defined crossover kinetics in the case of monomers T, D, and E and a subsequent good polymerization after the crossover reaction in the case of monomer E. The presented system allows a simple evaluation and monitoring of crossover reactions in ROMP-based polymerization reactions.

Tunable, temperature-responsive polynorbornenes with side chains based on an elastin peptide sequence.

Random copolymers made by living ring-opening metathesis polymerization of norbornene monomers containing either the elastin peptide sequence -(VPGVG)- or pentaethylene glycol (see scheme; Mes=mesityl, pyr=pyridine) exhibit a lower critical solution temperature (LCST). The LCST can be easily modified by varying the ratio of the co-monomers in the polymer feed.

Synthesis and palladium‐catalyzed addition polymerization of norbornene carrying epoxy moiety

AbstractA norbornene monomer carrying epoxy moiety 1 was successfully synthesized from 5‐norbornene‐2‐carbardehyde by treating it with thioylide. With using a catalytic system consisted of palladium (II) acetate/tricyclohexylphosphine/triphenylcarbenium tetrakis(pentafluorophenyl)borate, homopolymerizations and copolymerization of 1 and 5‐butyl‐2‐norbornene (BNB) were examined. The homopolymerization of 1 was slower than that of BNB presumably due to coordination of the epoxy moiety to the palladium‐center in competition with the CC double bond of norbornene. This deceleration became less significant in the copolymerizations with low initial feed ratios [1]0/[BNB]0, leading to successful formation of the corresponding copolymers having a rigid poly(norbornene) main chain and epoxy moiety in the side chains, of which composition ratios agreed with the feed ratios. Influence of the epoxy moiety of 1 on its Pd‐catalyzed addition polymerization was elucidated by studying the homopolymerization of BNB in the presence of 1,2‐epoxyhexane. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3982–3989, 2009

Alternating Ring-Opening Metathesis Copolymerization of Amino Acid Derived Norbornene Monomers Carrying Nonprotected Carboxy and Amino Groups Based on Acid−Base Interaction

Amino acid derived norbornene monomers having carboxy (1) and amino groups (2) were synthesized and subjected to ring-opening metathesis copolymerization with various feed ratios using the Grubbs second generation ruthenium catalyst. The M(n)'s of the copolymers ranged from 5300 to 9400 (M(w)/M(n) = 1.40-1.69). The monomer conversion and M(n) of the copolymer were maximized when the monomer feed ratio was 1:1. The monomer unit ratios in the copolymers were almost 1:1 at 10% conversion, irrespective of the feed ratios. The monomer reactivity ratios r(1) and r(2) were estimated to be 0.08 and 0.02, which confirmed that alternating copolymerization occurred. It is considered that alternating copolymerization is brought about by the acid-base interaction between the monomers and/or between the propagating polymer end and the incoming monomer.

ROMP of Norbornene Monomers Carrying Nonprotected Amino Groups with Ruthenium Catalyst

Amino acid-derived novel norbornene monomers (1a-2b) having nonprotected amino groups, together with tert-butoxycarbonyl (Boc) protected ones (1a-Boc-2b-Boc) were synthesized and polymerized by ring-opening metathesis polymerization using the Grubbs second generation ruthenium catalyst. The l-alanine-derived endo,endo-monomer 1a with amino groups gave no polymer, while the exo,exo-isomer 1b gave a polymer by raising the catalyst concentration. N-Methyl-l-alanine-derived 2a and 2b carrying secondary amino groups gave polymers in yields higher than 1a and 1b. On the other hand, Boc-protected 1a-Boc-2b-Boc gave the polymers in almost quantitative yields irrespective of the stereo structure (endo, exo) as well as the absence and presence of methyl group at the nitrogen atom. 1H−1H COSY NMR spectroscopic analysis and molecular mechanics calculation indicated that the polymers were syndiotactic.

UV-Induced Modulation of the Refractive Index and the Surface Properties of Photoreactive Polymers BearingN-Phenylamide Groups

Poly(N,N′-diphenyl-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxamide) was prepared as a functional polymer containing photoreactive arylamide groups. Under 254 nm UV irradiation, the arylamide groups undergo a photo-Fries rearrangement which yields aminosubstituted ketones as the reaction product. In thin films of the polymer, the photoreaction leads to a significant increase of the refractive index n by Δn = +0.10 which is unusually large for polymeric materials and more than sufficient for optical applications such as waveguiding. Due to the photogeneration of aminoketone groups, the chemical reactivity of the polymer is also enhanced after the irradiation step. This was employed for a selective postexposure modification of polymer films with acid chlorides and fluorescamine. In combination with photolithographic techniques, a structured surface functionalization was demonstrated. By reaction of the amino groups with bicyclo[2.2.1]hept-5-ene-2-carboxylic acid chloride a polymer surface bearing pendant norbornene units was created. Using the ring opening metathesis polymerization technique (ROMP), the immobilized norbornene moieties were successfully employed in a grafting-from polymerization of norbornene monomers. Photoreactive polymers bearing N-phenylamide groups are of interest for photolithography, optical applications such as waveguiding and holographic data storage, and for site selective surface functionalization.

Synthesis, Characterization and Radical Scavenging Ability of 3,5-di-tert-Butyl-4-hydroxyphenoxy-Functionalized Polynorbornenes Synthesized Using Ring-Opening Metathesis Polymerization

Novel norbornene derivatives bearing a 3,5-di-tert-butyl-4-hydroxyphenoxy (DBHO) group were synthesized and used as sterically hindered phenol functionalized norbornene monomers (1–4). The ring-opening metathesis polymerization (ROMP) of these functional monomers was carried out with a typical ruthenium catalyst (bis(tricyclohexylphosphine)benzylidene ruthenium (IV) dichloride, a Grubbs first-generation catalyst) to prepare sterically-hindered phenol-functionalized polymers possessing radical scavenging function. The resulting polymers bearing a DBHO side-chain were characterized by means of gel-permeation chromatography, 1H-NMR and 13C-NMR. The radical scavenging ability of polymers was determined using the α,α-diphenyl-β-picrylhydrazyl (DPPH⋅) free radical. Due to the electron-donating effect of the oxygen atom located in the para-position of phenol, the resulting polymers showed high efficiency to scavenge DPPH⋅free radical. The molecular weight of polymers was dependent on the molar ratio of monomer to catalyst ([M]/[C]), and the ROMP activity was dependent on the stereostructure of monomers themselves.