Carbodiimide Groups Research Articles

Functional electrolyte: Design of corrosion inhibition additives to protect Cu current collectors in over-discharged state

Lithium-ion secondary batteries are increasingly being used not only for ICT devices but also for large power sources such as EVs. Typically, the battery module discharge termination voltage is fixed in the device/power supply, but the sequentially connected single cells in the assembled battery may become over-discharged, thus there is a concern that the battery performance is degraded by the dissolution of the Cu current collector. Cu ions diffuse into the electrolyte due to the dissolution of the Cu current collector and precipitate on the anode during charging. This causes blackening of the Cu surface and an increase in cell resistance, and if it progresses further, it may lead to a short circuit. Therefore, we searched for an additive that would improve the battery performance by suppressing the dissolution of Cu, which causes a short circuit during over-discharge. Since 1999, we have proposed a "functional electrolyte" in which a small amount of an additive with a new function is added to the electrolyte. In this work, we focused on additives with carbodiimide groups (-N=C=N-) that prevent dissolution of the Cu collectors during over-discharge and improve the battery performance, and report the finding that N,N′-dicyclohexylcarbodiimide (DCC) exhibits such a unique behavior.

Tuning of water resistance and protein adsorption capacity of porous cellulose nanofiber particles prepared by spray drying with cross-linking reaction

Porous particles composed of 2,2,6,6-tetramethylpiperidinyl-1-oxyl-oxidized cellulose nanofiber (TOCN) as building block, i.e., porous TOCN particles, are attracting attention due to their environmental friendliness, superior properties, such as easy handling, large surface area, and high adsorption capacity. However, the instability of TOCNs in aqueous environments limits their applications. An effective solution to improve water resistance of TOCN particles is to reduce the hydrophilicity of TOCNs by forming chemical bonds with a cross-linker. In this study, Carbodilite, a common, easy-to-use, commercially available cross-linker with carbodiimide groups, was used to investigate a chemical cross-linking strategy for porous TOCN particles prepared by spray drying. The water resistance of cross-linked TOCN particles was evaluated through morphological observation by SEM images. The presence of polycarbodiimide significantly increased water resistance of cross-linked TOCN particles up to 24 h. This study demonstrates the trade-off between water resistance and adsorption efficiency according to cross-linker concentrations. These data are useful for interface science of TOCNs in liquids, assisting in controlling specific properties of porous TOCN particles for particular applications in adsorption and separation.

Topologically Enhanced Cation–π Interactions for Developing High‐Performance Underwater Adhesive

AbstractCation–π interactions provide an excellent way to develop high‐performance underwater adhesives. Although numerous underwater adhesive systems are designed based on cation–π interactions, they still lack precise design of the adhesive polymer backbone and topological control of the adhesive polymer. In this study, a novel short‐chain adhesive polymer with excellent underwater adhesion is developed based on the topologically enhanced cation–π interactions. Dihydrocaffeic acid containing catechol is incorporated into a short‐chain cationic polymer of polycarbodiimides through the nucleophilic reactions between carboxyl and carbodiimide groups to produce a catechol‐decorated cationic adhesive polymer (CCAP). The unique molecular structure of the CCAP confers the adhesive system strong cohesion and topologically enhanced cation–π interactions, leading to excellent underwater adhesion. Fe3+ is introduced into the adhesive system to promote the coordination of catechol and the oxidative crosslinking of catechol to further improve the cohesion of the CCAP. In addition, based on the synergy between reversible noncovalent bonds and the irreversible oxidative crosslinking system, the prepared adhesive can also act as a high‐strength hot‐melt adhesive, which maintains nearly 90% of its adhesion strength after 10 attachment–detachment cycles, showing its great potential for use as a sustainable reusable dismountable adhesive. This study provides a novel strategy to develop high‐performance underwater adhesive with temperature sensitivity.

New developments in chemical modification of fire-safe rigid polyurethane foams

This work reports the preparation of polyurethane–polyisocyanurate (PUR–PIR) foams containing different amounts of flame retardants (FRs) and a layered silicate nanoclay. An environmentally friendly blowing agent, a mixture of 1,1,1,3,3-pentafluorobutane and 1,1,1,2,3,3,3-heptafluoropropane (HFC 365/227), with small amount of water was used. The flame retarded PUR–PIR foams showed better fire resistance in comparison to classical PUR and unmodified PUR–PIR foams without deterioration of their functional properties. It was observed that when nanoclay was used in conjunction with flame retardants containing reactive bromine and phosphorus compounds, and zinc stannate, the flammability was significantly reduced. Expandable graphite was also used in some samples. As control samples for reference purposes three foam systems without any flame retardant were frothed: PUR, PUR–PIR and foams PUR–PIR modified by carbodiimide groups.

Polymer Interdiffusion vs Cross-Linking in Carboxylic Acid−Carbodiimide Latex Films. Effect of Annealing Temperature, Reactive Group Concentration, and Carbodiimide Substituent

This article describes the results of experiments examining the competition between the polymer interdiffusion and a cross-linking reaction in poly(2-ethylhexyl methacrylate) latex blend films in which the reactive groups (carboxylic acid and carbodiimide groups) are present in separate latex particles. In this system, polymer diffusion is necessary to bring the reactive groups into proximity, but the reaction creates long chain branches and gel that retard or inhibit further polymer diffusion. To enable measuring polymer diffusion rates by the energy transfer method, the methacrylic acid-containing particles were also labeled with a donor dye, and the −NCN-containing particles were labeled with an acceptor dye. Along with the extent of polymer diffusion, we monitored the growth in gel content as well as the consumption of carbodiimide groups. High gel content in the final film was promoted by factors that maximize the rate of polymer diffusion relative to the rate of the cross-linking reaction: high annealing temperature, low functional group content, and less reactive carbodiimide groups.

B/C/N Materials and B4C Synthesized by a Non-Oxide Sol−Gel Process

B-trichloroborazene B3N3H3Cl3 reacts with bis(trimethylsilyl)carbodiimide Me3Si−NCN−SiMe3 in THF or toluene, or without any solvent, to form non-oxide gels. The xerogels, amorphous B/C/N materials, and (semi)crystalline pyrolysis products were characterized using infrared (FTIR) and Raman spectroscopy, 11B- and 15N-nuclear magnetic resonance spectroscopy (NMR), X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elemental analysis. In addition, the pyrolysis process was investigated through thermal gravimetry coupled with mass spectrometry (TG−MS). The xerogels consist of a three-dimensional polymeric network of borazene rings linked by carbodiimide groups. Interestingly, the sol−gel transition is phenomenologically analogous to oxide systems and the polymers are almost free of chlorine and trimethylsilyl endgroups. Pyrolysis at 1200 °C provides an amorphous ceramic with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. This material starts to crystallize around 1600 °C under evolution of nitrogen, forming nearly pure B4C at 2000 °C. Very small amounts of amorphous carbon as well as carbon nanotubes were also present.

Heterocyclization of functionalized vinylic derivatives of imidazo.

Heterocyclization of functionalized vinylic derivatives of imidazo[1,2-a]pyridines was explored experimentally and theoretically using semiempirical AM1 and ab initio methods. A range of functionalized vinylic derivatives (azido, amino, and carbodiimide groups) were prepared for conversion into pyrroloazaindoles 19-22, imidazo[1,x]-, (x = 5, 6, 7, 8), [2,6]-, and [2,7]naphthyridines 28-30, 35-38 by thermal reaction. In the case of vinylic groups in the 5 position, peri annulation also was observed. The experimental and theoretical data are compared and discussed.

A Sol–Gel Route to B4C

B-trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non-oxide gels (see scheme). The xerogels consist of a polymeric network of borazine rings linked by carbodiimide groups. Pyrolysis at 1200°C provides amorphous ceramics with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. At 2000°C pure B4C is formed.

A Sol-Gel Route to B4C

B‐trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non‐oxide gels (see scheme). The xerogels consist of a polymeric network of borazine rings linked by carbodiimide groups. Pyrolysis at 1200°C provides amorphous ceramics with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. At 2000°C pure B4C is formed.

Synthesis, characterization, and stability of carbodiimide groups in carbodiimide-functionalized latex dispersions and films

Synthesis, characterization, and stability of carbodiimide groups in carbodiimide-functionalized latex dispersions and films

Synthesis, characterization, and stability of carbodiimide groups in carbodiimide-functionalized latex dispersions and films

Cyclohexylcarbodiimidoethyl methacrylate (CCEMA) and t-butylcarbodiimidoethyl methacrylate (t-BCEMA) were prepared in a two-step synthesis. These monomers were then used to prepare carbodiimide-functionalized PBMA and PEHMA latex particles, employing two-stage emulsion polymerization, with the carbodiimide–methacrylate monomers being introduced only in the second stage under monomer-starved conditions. During emulsion polymerization, the carbodiimide moiety (NCN) was found to be unstable at pH 4, but stable when the pH of the dispersion was increased to 8, using NaHCO3 as the buffer. Survival of NCN group against hydrolysis during the polymerization, and during storage in the dispersion, was enhanced by using EHMA as the comonomer (more hydrophobic) and the t-butyl carbodiimide derivative. The t-butyl group provides more steric hindrance to the hydrolysis reaction. A decrease in the reaction temperature from 80°C to 60°C was also found to increase the extent of NCN group incorporation during emulsion polymerization. Under ideal conditions, more than 98% of the NCN groups in the monomer feed are successfully incorporated into the latex. When these latex particles are mixed with a COOH containing latex and allowed to dry, polymer diffusion leading to crosslinking occurs. Films annealed at 60°C reach a gel content of 60% in 10 h. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 855–869, 2000

Si and N K-XANES spectroscopic study of novel Si–C–N ceramics

Abstract X-ray absorption near edge structure (XANES) measurements at the Si and N K-edges of ternary Si–C–N compounds are applied to analyze the changes of structural units owing to the thermally induced ceramization of silicon dicarbodiimide Si(NCN) 2 at temperatures up to 1600°C. Samples synthesized below 800°C show an environment of silicon consisting of carbodiimide (NCN) groups. Further annealing leads to a crystalline phase, Si 2 CN 4 , which combines the structural units (Si–N–Si) and (Si–NCN). Recorded spectra of samples annealed at temperatures higher than 1200°C show the decomposition of Si 2 CN 4 . The material then transforms to a Si 3 N 4 –SiC composite material through an intermediate amorphous Si–C–N phase.

An Improved Technique for the Determination of Isocyanurate and Isocyanate Conversion by Photoacoustic FTIR

Conventional rigid polyisocyanurate (PUIR) foams blown with HCFC-141b often suffer from poorer compressive strengths, dimensional stability and inferior flammability properties when compared to foams blown with CFC-11. It is often hypothesized that these properties can be improved by increasing the isocyanurate (or "trimer") conversion by means of catalyst optimization and increased isocyanate index. A convenient, yet reliable method for the determination of the amount of isocyanurate in a PUIR foam has been missing in this industry for a long time, though several attempts have been documented in the literature. The purpose of this paper is to introduce an improved isocyanurate conversion test by photoacoustic Fourier Transform Infra Red (FTIR) technique. This involves creating a baseline through three anchor points at approximately 1637 cm−1, 1469 cm−1, and 1349 cm−1. The absorbance of the isocyanurate peak at 1410 cm−1 is taken relative to the absorbance of the phenyl peak at 1602 cm−1. The phenyl peak is preferred to the urethane peak because the absorbance of phenyl groups in a foam is inherent to the amounts of polyols and isocyanates used in the foaming reaction, whereas the urethane linkages in the foam are created by a reaction between the two and are, therefore, variable depending on the extent of the reaction in the presence of catalysts and possibly water. In addition, the relative ratios of the absorbances of isocyanate end groups (at 2277 cm−1) and carbodiimide groups (at 2136 cm−1) to the phenyl groups can also be determined by generating a baseline through the anchor points at approximately 2470 cm−1, 2207 cm−1 and 2000 cm−1. This allows one to gain a better assessment of the overall kinetics of the isocyanate reactions and creates opportunities to improve the isocyanurate conversion through formulation optimization. The method is not limited to polyisocyanurate foams, as isocyanate conversion is an important parameter to follow in polyurethane foams as well, especially in all carbon dioxide blown foams. The method was found to be quite reproducible, and further statistical analysis to ensure the validity of this technique is under way.

Study of Pyrolytic Conversion of Polycarbodiimide to Glass-like Carbon Film

We have developed a new starting polymer for glass-like carbon film; poly-carbodiimide (PCDI). The purposes of this paper are to determine the structure of the carbonized PCDI and to reveal the mechanism for the carbonization.After heat treatment at 1000°C, the total yield was ca. 75 % and the density reached 1.78g/cm3. These values are much higher than the ordinary starting resins, such asphenolic resin, cellulose and PVC. The carbonized PCDI also has higher mechanical strength and gas permeability. These properties can be explained by the high density of the crystalline and the inter-crystalline structures.The IR spectrum shows that two kinds of crosslinkage, dimer and trimer, are formed densely below 230°C in air. These crosslinkages come from reactive carbodiimide groupsin the molecular main chain of PCDI. Partial oxidation of the sample promote the formation of the trimer from the dimer and the carbodiimide groups, so that the sample becomes more heat stable.

Slab Foams Prepared from Modified TDI (Cushion Fatigue Study)

The presence fo crosslinked groups in flexible slab foams has been suspected to be a cause of poor fatigue properties. This study has provided proof that this is indeed the case. TDI modified by the addition of biuret, allophanate or carbodiimide groups was prepared. Thus, measured amounts of these groups could be introduced into the foams. In standard formulations, it was found that relatively small amounts of biuret and allophanate groups had a significant adverse effect on fatigue, shrinkage and air flow of the resulting foams

New polymers and polymeric systems based on epoxide oligomers and polyheteroarylenes. Review

The authors look at a new reaction of the oxirane cycle with an ester, amide, carbodiimide and other polar groups containing heteroatoms in the chains of the corresponding polymers and model compounds. The possible mechanism of these reactions and their catalysis is discussed. Ways of modifying the corresponding linear polymers by epoxide oligomers are analysed. The properties of the polymers formed and the materials based on them are described.

Macroheterocycles; XXVIII. Coronands with Carbodiimide Groups and Their Chemical Transformations

Coronands with two carbodiimide groups were prepared by the reaction of macrocyclic thioureas with triphenylphosphine in the presence of carbon tetrachloride and triethylamine. The reaction of these compounds with water, alcohols and amines afforded coronands containing urea, isourea and guanidine groups in high yields.

Intramolecular reaction between nitro and carbodi-imide groups; a new synthesis of 2-arylbenzotriazoles

1-(2-Nitrophenyl)-5-phenyltetrazole (5b) decomposes when heated to give nitrogen, carbon dioxide, and 2-phenylbenzotriazole (6) in high yield. This new molecular rearrangement proceeds via 2-nitrophenyl(phenyl)carbodi-imide (8). Other precursors of this carbodi-imide, i.e. oxadiazolone (10), oxadiazolethione (11), oxathiadiazole 2-oxide (12), and the aminimide (16), and carbodi-imide itself, all give 2-phenylbenzotriazole (6) on thermolysis, the last three in high yield. This reaction is general for diarylcarbodi-imides with an ortho nitro group, and their precursors, and it provides a useful new route to 2-arylbenzotriazoles. A sequence of electrocyclic ring closing and opening reactions (Scheme 5) is proposed as the mechanism of this process. The key intermediate, 2-phenyl-1,2,4-benzotriazin-3-one 1-oxide (19), has been isolated from a careful thermolysis of (12) in toluene; in solution it is in reversible equilibrium with the ring-opened form (20). This new nitro-carbodi-imide group interaction has been extended to the more stable nitrobiphenyl(phenyl)carbodi-imide (25) and nitronaphthyl(phenyl)-carbodi-imide (24) which, on flash vacuum pyrolysis, give benzimidazo[1,2-f]phenanthridine (29) and benz[cd]indazole 1-oxide (32) respectively, in new rearrangements.

Thermal transformations of compounds modelling major fragments of network polymers, based on oligo- and polycarbodiimides

Abstract The thermal, thermo-oxidative and thermohydrolytic stability of diphenylcarbodiimide, the cyclic dimer of diphenylcarbodiimide, hexaphenylisomelamine and hexaphenylmelamine, which model major fragments of network polymers based on oligo- and polycarbodiimides were studied over the 250–550° temperature range. Gaseous, liquid and solid products of the decomposition of these compounds were identified. It was established that under thermolysis conditions in a vacuum, the stabilities of the model compounds were almost the same, whilst hexaphenylmelamine displayed the highest stability towards thermo-oxidation and thermohydrolysis and diphenylcarbodiimide, the least. The results obtained permit recommendation of ways of performing directed crosslinking of linear polymers with carbodiimide groups in the chain, in order to obtain the most thermally stable systems.

The thermal degradation of a polythiolcarbamate

AbstractOn pyrolysis at 300° under nitrogen the polythiolcarbamate from methylenebis(4‐phenyl isocyanate) and 1,6‐hexanedithiol decomposed into carbon dioxide, carbonyl sulfide, 6‐mercapto‐1‐hexene, tetrahydro‐2‐methyl‐1‐thiapyran, thiepane, 1,6‐hexanedithiol, and an intractable residue. Carbodiimide and amine groups were shown to be intermediates in the formation of the residue. A quantitative study of the degradation indicated that about 80% of the thiolcarbamate groups decomposed by splitting into isocyanate and mercaptan moieties. Further reaction of the isocyanate moiety produced the carbon dioxide and carbodiimide groups. The remaining thiolcarbamate groups formed carbonyl sulfide, and amine and olefin groups, probably by a direct ester type of degradation. The resulting 6‐mercapto‐1‐hexene was the source of the cyclic sulfides.