Norbornene Units Research Articles

Maleopimaric acid trimethyl ester

The title compound, C27H40O6, contains two fused cyclo­hexane rings with chair conformations, fused to a norbornene ring system. The ester groups that are attached to the norbornene unit are in a cis configuration. There are two molecules in the asymmetric unit. The structure is stabilized by C—H⋯O inter­molecular hydrogen bonds and van der Waals forces.

Copolymerization of ethene with norbornene using palladium(II) α-diimine catalysts: Influence of feed composition, polymerization temperature, and ligand structure on copolymer properties and microstructure

Four cationic palladium(II) α-diimine complexes, [{ArNC(R)–C(R)NAr}Pd(Me)(CH3CN)]BAr4f (1, R=H, Ar=2,6-Me2C6H3, BAr4f=B[3,5-C6H3(CF3)2]4; 2, R=CH3, Ar=2,6-iPr2C6H3; 3, R=CH3, Ar=2-tBuC6H4; 4, R,R=An, Ar=2,6-iPr2C6H3) were used for the copolymerization of ethene with norbornene. The copolymerization behavior of the catalysts and the influence of the polymerization temperature were investigated. The copolymers were characterized using 13C NMR spectroscopy, differential scanning calorimetry, and gel permeation chromatography techniques. Sterically demanding ortho -N-aryl substituents and rigid bulky bridge units increase the copolymer molar masses, while the incorporation level of norbornene is decreased. Microstructures with isolated norbornene units and alternating sequences are predominant. Less bulky substituted catalysts yield copolymers with higher norbornene contents and lower molar masses. Norbornene diblock sequences are dominant which are exclusively racemic connected, indicating that the insertion proceeds under chain end control. Optimal polymerization results are achieved at temperatures between 10 and 30°C, while temperatures below 0°C result in lower polymerization rates and molar masses. Above 30°C, activities, molar masses, and norbornene incorporation decreases due to catalyst decomposition.

Molecular Dynamics in Cyclic Olefin Copolymer

Nuclear magnetic resonance, broadband dielectric spectroscopy and dynamic-mechanical thermal analysis were employed to study molecular dynamics of ethylene-norbornene copolymer. The analysis of experimental data indicates existence of three motional processes denoted as fi; fl, and ∞ in order of decreasing temperature. The fi relaxation is related to the dynamic glass transition, while the fl relaxation, observed only for the untreated sample, is assigned to short range segmental motions involving norbornene units. The ∞ relaxation is due to very local motions of ethylene units e.g. trans-gauche isomerization, similar to those responsible for ∞ relaxation in polyethylene. The rate of motion accountable for ∞ process, follows the Vogel{Fulcher{Tammann equation, similarly to fi transition, indicating cooperative nature of the motion.

Crystal Structure of Alternating Ethylene−Norbornene Copolymer

Models for the crystal structure of alternating isotactic ethylene−norbornene copolymers (ENCs) are presented. Oriented fibers of ENCs samples have been obtained, and the corresponding X-ray fiber diffraction pattern has been reported. A value of the chain axis periodicity of 8.9 Å has been evaluated. A geometrical analysis and conformational energy calculations have shown that both isotactic and syndiotactic ENC chains assume nearly extended conformations having 2-fold helical s(2/1)m and glide plane tcm symmetries, respectively. Both conformations account for the experimental chain axis periodicity of 8.9 Å. The crystal structure is mainly defined by the packing of the quasi-spherical norbornene units. The barycenters of the norbornene units are arranged on a face-centered crystalline lattice, producing a short-range three-dimensional positional order. Different kinds of structural disorder are present in the structure. A short-range order in the average positioning of the norbornene rings is maintained, while disorder in the positioning of the carbon atoms of the ethylene units is present. The ethylene units may assume different positions along a and b axes of the unit cell and connect with equal probability a given norbornene unit with any of its next neighbors, producing orientational disorder of the polymer chains as well as of the spherical norbornene units. The amount and the kind of disorder depend on the microstructure of the chains and on the condition of crystallization. The structure may be described by limit disordered models of packing, in unit cells having a = b = 9.4 Å and c = 8.9 Å or a = 9.3 Å, b = 9.5 Å, and c = 8.9 Å. and statistical orthorhombic or tetragonal space groups Bmcm or I4/mmm. The partial threedimensional order, guided by the ordered positioning of the ball-like norbornene units, is obtained even though the polymers are configurationally disordered, provided that they have a regular alternation of the comonomeric units.

Dissolution behavior of tetrafluoroethylene-based fluoropolymers for 157-nm resist materials

We have synthesized various main-chain fluorinated polymers and studied base-resin properties, such as transparency at 157 nm, solubility in a standard alkaline developer, and lithographic performance. Main-chain-fluorinated polymers were synthesized by copolymerization of tetrafluoroethylene (TFE) with cyclic monomers, especially newly synthesized norbornene derivatives. We studied the correlation between p K a(OH) and the solubility of the copolymers of TFE and functional (fluoroalkyl alcohol group) norbornenes. Their solubility depends on the p K a value of the fluoroalkyl alcohol groups. We studied the impact of the polymerization initiators on base-resin properties. High transparency was obtained by using the fluorocarbon initiator. It was also confirmed that the monocyclic component improves dry-etch resistance and that fluorination at the terminal groups improves alkaline solubility. In addition, we found that the development characteristics of TFE/norbornene copolymers were significantly improved by the stereoselective ( endo versus exo) partial protection of the hydroxyl groups in the fluoroalkyl alcohol moiety attached to norbornene unit. The polymer protected only in the exo position of the norbornene unit in the copolymer had a higher R max and a higher contrast. Positive-working resists based on these fluoropolymers were developed and 55 nm dense lines could be delineated by exposure at 157 nm wavelength with an alternating phase shift mask on a 0.9 NA 157 nm exposure tool.

Ruthenium(II) dipyridoquinoxaline-norbornene: synthesis, properties, crystal structure, and use as a ROMP monomer.

The synthesis, X-ray structure, and electrochemical and photophysical characterization of [Ru(phen)(2)dpq-n][PF(6)](2) (phen = phenanthroline, dpq-n = dipyridoquinoxaline-norbornene) are described. This complex contains a Ru(phen)(3)(2+) moiety in close conjugation with a norbornene unit and is the first example of a Ru(II) diimine complex capable of undergoing ring-opening metathesis polymerization. Luminescence studies of this complex showed an increase in quantum efficiency in polar solvents and in water. Preliminary ring-opening metathesis polymerization studies, carried out at low monomer-to-initiator ratio, showed the formation of an oligomeric mixture composed mainly of the dimer of this complex. This dimer exhibits photophysical and redox properties similar to those of the monomer, indicating that the Ru(phen)(3)(2+) moiety remains intact during the polymerization.

Synthesis of well-defined graft co-polymers via coupled living anionic and living ring-opening metathesis polymerisation

The synthesis of polystyrene (PS) macromonomers functionalised with a norbornene (Nbe) unit and their living ring-opening metathesis polymerisation (ROMP) to produce comb graft co-polymers is described. Macromonomers comprising of one PS chain per Nbe unit and two PS chains per Nbe unit have been synthesised with a variety of chain lengths of PS. These macromonomers have been subjected to ROMP initiated with three different catalysts and the effect of catalyst along with the effect of solvent, concentration and time on the extent and rate of macromonomer polymerisation have been studied. Molecular weight analysis of the comb graft co-polymers by triple-detection size-exclusion chromatography (SEC) with light scattering has greatly improved the ease and accuracy of interpretation of results.

The Dissolution Behavior of Tetrafluoroethylene-based Fluoropolymers for 157-nm Resist Materials

Main-chain-fluorinated base-resins, using the copolymer of tetrafluoroethylene and functional (hexafluoroisopropanol (HFA) group) norbornene, were synthesized. Partial protection of the hydroxyl group as an ethoxymethyl group was achieved by two methods: by copolymerization (Method A) or by polymer reaction (Method B). The partial protection by copolymerization was conducted by copolymerizing TFE with a mixture of protected and unprotected monomers (Method A, copolymerization). Partial protection was also carried out by reacting the hydroxyl group of the polymer, which is composed of TFE and unprotected monomers with ethoxymethyl chloride in the presence of an amine (Method B). In the polymer reaction, only the exo position of the norbornene unit was protected. Their fundamental properties, such as transparency at 157 nm and solubility in a standard alkaline developer, were characterized and studied. High transparency, i.e., absorbance better than 0.4 μm-1, was achieved with both methods. However, the polymer prepared by the polymer reaction (Method B) was deprotected more quickly; it also had a higher dissolution rate and stronger development contrast than the polymer prepared by copolymerization (Method A). Positive-working resists based on these fluororesins were developed and 55 nm dense lines could be delineated by exposure at 157 nm wavelength with alternating phase shift mask on a 0.9 NA 157 nm exposure tool.

Ethene–norbornene copolymerizations using two different homogeneous metallocene catalyst systems and investigations of the copolymer microstructure

Ethene–norbornene copolymerizations were carried out at various ethene pressures by using the homogeneous catalyst systems iPr[(3-iPr-Cp)Ind]ZrCl2/MAO and rac-iPr[Ind]2ZrCl2/MAO. The copolymer microstructures were analyzed by 13C NMR spectroscopic investigations. On the basis of the obtained results, it could be concluded that copolymers generated with the metallocene iPr[(3-iPr-Cp)Ind]ZrCl2 contain norbornene microblocks with a maximum length of two norbornene units in spite of high norbornene excess in the norbornene and ethene feedstock composition. In the microstructures of copolymers generated with the metallocene rac-iPr[Ind]2ZrCl2 norbornene microblocks with a length of three norbornene units have been detected. Results have shown that the amount of norbornene triblocks in the copolymer chain as well as the stereochemical connection of the norbornene triblocks depends on the monomer concentration and the polymerization temperature.

Position-Addressable Nano-Scaffolds. I. The Preparation of N,O-, N,C- and N,N-Bridged Sesquinorbornadiene Succinimides as Compact, Highly Functionalized Addressable Building Blocks

Succinimide-functionalized N,O-, N,C-, and N,N-bridged benzo[2]polynorbornanes (benzosesquinorbornadienes) are reported for the first time and are prepared by the cycloaddition of either five-membered cyclic 1,3-dienes onto N-substituted benzo-7-azanorbornadienomaleimides or N-substituted isoindoles onto the appropriate norbornadienomaleimides. These products contain an end-fused norbornene (or a 7-substituted relative) and have been designed to act as alkene BLOCKs for the production of nano-scaffolds with up to six addressable sites supplied by each norbornene unit. The N-bridges in these BLOCKs (and their coupled products) allow N-substituent mobility by invertomerization of the sp3 nitrogen whereas the N-substituents on the succinimides are attached to an sp2 nitrogen atom and remain static. Preferred invertomer geometry can be determined using molecular modelling.

First Examples of Homogeneous Catalytic Cyclotrimerization and Polymerization of Phenylacetylene and Copolymerization of Phenylacetylene and Norbonene with Dinuclear Complexes Containing Unbridged Metal-Metal Quadruple Bond

First examples of application of dinuclear complexes containing unbrigded metal-metal quadruple bond as catalysts in cyclotrimerization, oligomerization and polymerization of substituted acetylene are reported. The d4-d4 dinuclear complexes (Bu4N)2[Re2X8] (1) (1a, X = Cl; 1b, X = Br and 1c, X = I) show low activity and the complex [Mo2Cl4(MeOH)2(PPh3)2] (2) medium activity in cyclotrimerization and oligomerization of phenylacetylene (PA). In contrast, the tungsten-based d4-d4, complex Na4[W2Cl8] (3) exhibits high polymerization activity (polymer yield above 90%) and ca 75% cis-selectivity in tetrahydrofuran. The activity and cis-stereoselectivity of these single-component catalysts decrease in the order 3 >> 2 >> 1, which is proportional to the metal-metal quadruple bond propensity towards ligand addition reactions. Complex 3 induces metathesis polymerization of norbornene (NBE) to poly(cyclopentene-1,3-diylvinylene) with 82% cis-selectivity and copolymerization of PA and NBE to almost all-cis high-molecular-weight copolymer containing cyclopentene-1,3-diylvinylene units, which is free of longer sequences of both PA and NBE units. This suggests that also homopolymerization of PA with 3 proceeds by the metathesis mechanism and that the PA/NBE copolymer structure is close to the alternating one.

13C NMR Studies of Ethene/Norbornene Copolymers using13C-Enriched Monomers: Signal Assignments of Copolymers Containing Norbornene Microblocks of up to a Length of Three Norbornene Units

Ethene and norbornene were copolymerized at 0.8 bar ethene absolute pressure using metallocene catalysts that produce microstructures containing norbornene blocks, particularly rac-Me2Si[Ind]2ZrCl2/MAO, iPr[CpFlu]ZrCl2/MAO and iPr[CpInd]ZrCl2/MAO. Intensive 13C NMR spectroscopic investigations of the obtained copolymers were performed and norbornene di- and triblock sequences detected clearly. Several copolymerization experiments were carried out by using 13C1-enriched ethane, or 13C5/6-enriched norbornene, respectively. Thus, resonances of the norbornene carbon atoms C5/C6 and the ethene carbon atoms Ca/Cb, which overlap extensively in the 13C NMR spectra, could clearly be differentiated. In addition, further copolymerizations with natural monomers were performed at 2 bar ethene excess pressure to investigate the influence of the monomer concentration on the microstructure. By comparing the 13C NMR spectra of copolymers obtained under different conditions, assignments of most resonances were achieved. These 13C NMR studies made it possible to assign norbornene triblock resonances with differing stereochemical connections such as meso,meso and rac,meso which have not been mentioned in previous works. The results led to new insights about the copolymer microstructure and allow development of a scheme showing the ethene/norbornene microstructures depending on the various catalyst systems utilized, including the metallocenes iPr[(3-iPr-Cp)Flu]ZrCl2 and iPr[(3-tert-But-Cp)Ind]ZrCl2 which have been applied in previous publications.

Synthesis of nucleic-acid base containing norbornene derivatives as monomers for ring-opening-metathesis–polymerization

A series of norbornene derivatives containing nucleic-acid bases (thymine, adenine, cytosine, guanine, or uracil) have been prepared as monomers for ring-opening-metathesis–polymerization (ROMP). Many of the initially prepared monomers had poor solubility but this could be overcome by appropriate choice of a linker between the norbornene and base units. Some of the monomers were successfully polymerised to give homopolymers derived from nucleic-acid bases.

Stress-Strain Behaviour, Microhardness, and Dynamic Mechanical Properties of a Series of Ethylene-Norbornene Copolymers

Ten copolymers of ethylene and norbornene, synthesised by a metallocene catalyst, covering the composition range from 31 to 62 mol-% of norbornene, have been studied by stress-strain, microhardness and dynamic mechanical measurements. These copolymers show a single glass transition and the correlation between Tg and the norbornene content is quite good. The inclusion in the polymer chain of rigid norbornene units, with the corresponding increase in Tg, leads to considerably higher Young moduli and microhardness values in these cycloolefin copolymers. The same result is found for the yield stress: this parameter shows an increase by a factor of two in the studied copolymers. Two relaxations, α and γ have been found by means of dynamic mechanical analysis of these copolymers. The results show that the γ relaxation has a similar origin to that of polyethylene and therefore its intensity diminishes as the proportion of ethylene segments in the copolymers decreases. On the contrary, the α relaxation of the copolymers has a completely different origin than that of polyethylene. Thus, this relaxation represents the glass transition in the copolymers, associated with the amorphous character, while it is attributed to motions in the crystalline regions of the parent homopolymer, polyethylene.

Polymer electrolytes derived from polynorbornenes with pendent cyclophosphazenes: poly(ethylene glycol) methyl ether (PEGME) derivatives

A novel elastomeric polymer electrolyte was developed by the linkage of poly(ethylene glycol) methyl ether (PEGME) side chains and norbornene-based units to a cyclotriphosphazene ring, followed by polymerization of the norbornene units by ring-opening metathesis polymerization (ROMP). This yielded an organic polymer backbone with ion co-ordinative cyclic phosphazene side groups. Adjustment of the norbornene content in the starting monomer allowed the degree of branching and cross-linking to be controlled and, in turn, the mechanical properties of the material to be tuned. The polymers were complexed with fixed molar ratios of LiN(SO 2CF 3) 2 and LiSO 3CF 3 and examined as solid polymer electrolytes. Polymer gel electrolytes were then formulated by the addition of variable amounts of propylene carbonate to the polynorbornenes. Films of solvent-free and solvent-containing polymers were homogeneous, flexible and self-standing materials. The ionic conductivities of the solvent-free polymers were in the range of 4×10 −5 S/cm at 30°C in the presence of 40 mol% of LiSO 3CF 3 or LiN(SO 2CF 3) 2. The conductivities of the solvent-containing (gel) systems increased with increases in the propylene carbonate content to a value of 2×10 −3 S/cm at 30°C in the presence of 50 wt.% of propylene carbonate and with the use of LiN(SO 2CF 3) 2 at a constant O:Li + ratio of 8:1. Even with this high concentration of propylene carbonate, the electrolyte was a solid elastomer rather than a viscous liquid. In general, the conductivities are twice as high with the use of LiN(SO 2CF 3) 2 compared to LiSO 3CF 3. The T g values were determined by DSC analysis, and these decreased with increased amounts of propylene carbonate in the system.

Incorporation of Conformationally Constrained β-Amino Acids into Peptides

The use of norbornene units to induce the formation of β-sheet and β-turn type structures in peptides is discussed. The norbornene unit is readily prepared by a desymmetrization reaction and is easily incorporated into a peptide chain. Depending upon the exact nature of the norbornene unit, it is possible to form structures which resemble parallel β-sheets, antiparallel β-sheets or β-turns. Similar peptide analogues incorporating a cis-2-amino-cyclopropane carboxylic acid unit can also be prepared. As an illustration of the application of this chemistry, a short, asymmetric synthesis of conformationally constrained metalloprotease inhibitors is presented. Copyright © 2000 European Peptide Society and John Wiley & Sons, Ltd.

Functionalization and chemical modification of cyclo olefin copolymers (COC)

In this paper, we report two simple and effective bromination methods to brominate the cyclo olefin copolymer (COC). A suitable metallic catalyst can accomplish functionalization and chromophorization of the brominated COC. A 2nd NLO dye, Disperse Orange 3(DO3) containing the –NH2 functional group, has been grafted onto either the norbornene unit or the PE segment of the COC backbone successfully, by the palladium catalyst, Pd2(dba)2(Bis[dibenzylideneacetone] dipalladium). The observed low dye grafting content can be attributed to the higher hindrance of the norbornene ring.Based on UV results, the NLO–COC, having dye grafted onto the norbornene unit shows more red shift than that grafted onto the PE unit, probably due to greater shielding on the chromorphor.

Incorporation of conformationally constrained beta-amino acids into peptides.

The use of norbornene units to induce the formation of beta-sheet and beta-turn type structures in peptides is discussed. The norbornene unit is readily prepared by a desymmetrization reaction and is easily incorporated into a peptide chain. Depending upon the exact nature of the norbornene unit, it is possible to form structures which resemble parallel beta-sheets, antiparallel beta-sheets or beta-turns. Similar peptide analogues incorporating a cis-2-amino-cyclopropane carboxylic acid unit can also be prepared. As an illustration of the application of this chemistry, a short, asymmetric synthesis of conformationally constrained metalloprotease inhibitors is presented.

Norbornene-constrained cyclic peptides with hairpin architecture: design, synthesis, conformation, and membrane ion transport.

A novel family of hairpin cyclic peptides has been designed on the basis of the use of norbornene units as the bridging ligands. The design is flexible with respect to the choice of an amino acid, the ring size, and the nature of the second bridging ligand as illustrated here with the preparation of a large number of norborneno cyclic peptides containing a variety of amino acids in ring sizes varying from 12- to 29-membered, with the choice of the second bridging ligand being a rigid norbornene (11, 13a,b), an adamantane unit (7a,b and 8), or a flexible cystine residue (4a,b and 10). The presence of built-in handles (as protected COOH groups) permits the attachment of a variety of subunits as shown here with the ligation of Leu-Leu, Val-Val, or Aib-Aib pendants in 4b, 7b, and 13b, respectively. This novel class of constrained cyclic peptides are demonstrated to adopt beta-sheet- or hairpin-like conformation as shown by (1)H NMR and CD spectra. Membrane ion-transport studies have shown that the norborneno cyclic peptides 4b and 7b containing Leu-Leu or Val-Val pendants symmetrically placed on the exterior of the ring show high efficiency and selectivity in the transport of specifically monovalent cations. This property can be attributed to the hairpin-like architecture induced by the norbornene unit since the bis-adamantano peptide 15 containing two pairs of Leu-Leu pendants on the exterior is able to transport both monovalent (Na(+), K(+)) and divalent (Mg(2+)/Ca(2+)) cations.

Molecular Factors Affecting the Miscibility Behavior of Cycloolefin Copolymers

The mutual miscibility diagram is determined for binary blends of two ethylene/norbornene random copolymers, and their monomer sequence distribution is investigated by 13C NMR spectroscopy. The miscibility changes abruptly at a norbornene content of 50% where NMR measurements indicate a change in microstructure. When both copolymers have a norbornene content higher than 50%, all blends are miscible within the composition ranges available. A simplified version of the lattice cluster theory (LCT) is applied to this system. The computations indicate that the chain stiffness (arising from the rigidity and steric interactions of the norbornene units) exerts significant influence on the miscibility of these blends. Experimental miscibility diagrams agree reasonably with the LCT predictions.