Carbonyldiimidazole Research Articles

Design, synthesis, molecular docking, ADMET studies, and biological activity evaluation of new 2-({[3-aryl-1,2,4-oxadiazol-5-yl)methyl]thio}-1H-benzimidazoles and 6-amino-6-aryl-5,6-dihydro[1,6,2,4]oxathiadiazocino[4,5-a]benzimidazol-3(2H)-ones

Aryl amidoximes are active binucleophilic compounds used as a powerful and versatile reagent in synthesizing diverse heterocyclic compounds with pharmacological interest. Thus, a new series of 2-({[3-aryl-1,2,4-oxadiazol-5-yl)methyl]thio}-1H-benzimidazoles 5a-g was successfully synthesized from the reaction of (1,3-benzimidazol-2-ylthio)acetic acid (2) with aryl amidoximes 4a-g, respectively. The reaction is proceeded in dimethylformamide (DMF) in the presence of 1,1′-carbonyldiimidazole (CDI) as a coupling reagent. The unexpected products 6-amino-6-aryl-5,6-dihydro[1,6,2,4]oxathiadiazocino[4,5-a]benzimidazol-3(2H)-one 6a-c were formed through the reaction of acetic acid derivative 2 with arylamidoxime 4b,c,g in acetonitrile at room temperature or under reflux, using CDI as coupling reagent. Compounds 5g and 6a proved the most potent hypocholesterolemic agents, with significant hypolipidemic and hypotriglyceridemic influence. They represent promising candidates for establishing novel hypolipidemic derivatives and anti-atherosclerotic. Compounds 5g and 6a demonstrated the highest antioxidant effect, reaching 77 and 81% radical scavenging activity, respectively. Docking studies were also performed on the synthesized members to examine their binding interactions with their target enzyme, Niemann-Pick C1-like 1 (NPC1L1). Finally, physicochemical properties of the synthesized compounds were investigated in silico. The obtained results showed that most synthesized members had a positive drug-likeness profile.

Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’‐Carbonyldiimidazole Activated Fatty Acids

AbstractSynthetic model triacylglyceride oils are important compounds for applications in pharmaceutical and food chemistry. Herein, a practical and highly efficient methodology for the synthesis of saturated and unsaturated triacylglycerides utilizing saturated and unsaturated fatty acids activated by 1,1’‐carbonyldiimidazole (CDI) has been developed and applied in the synthesis of deuterated medium chain triglyceride (MCT) oil for studies of plant‐based and diary food emulsions. The deuterium labelled compounds were used to gain new insight into the mechanism of the reaction, which was confirmed by density‐functional theory (DFT) calculations.

Poly(propylene glycol)‐Based Non‐Isocyanate Polyurethane Ionenes: Thermal, Morphological and Conductive Properties

AbstractThe synthesis and characterization of a series of polyurethane ionenes using a non‐isocyanate approach is disclosed. Imidazole‐capped, urethane‐containing prepolymers are prepared by first reacting carbonyl diimidazole (CDI) with several poly(propylene glycol) (PPG) diols with variable molecular weight, followed by subsequent reaction with 3‐aminopropylimidazole (API). Polymerization with 1,4‐dibromomethylbenzene followed by anion exchange resulted in the desired polyurethane ionenes bearing the [NTf2] counteranion as a series of viscous liquids. NMR and FTIR spectroscopy are used to characterize the intermediates and final ionenes, including molecular weight determination by end‐group analysis. A single glass transition temperature (Tg), as determined by differential scanning calorimetry (DSC), is observed for each ionene (−38 to −64 °C) with the Tg decreasing with increasing PPG molecular weight. Thermogravimetric analysis (TGA) indicated a two‐step decomposition for each ionene, with the first being degradation of the PPG segment, followed by the urethane/ionic segment. Microphase separation is observed from x‐ray scattering profiles with Bragg distances that increased with increasing PPG molecular weight. Ionic conductivity is found to be inversely dependent upon DSC Tg at lower temperatures (RT and below); however, at higher temperatures, conductivity appears to be more dependent upon the ability of ionic aggregates caused by phase separation to interact.

Redox-sensitive self-assembled micelles based on low molecular weight chitosan-lipoic acid conjugates for the delivery of doxorubicin: Effect of substitution degree of lipoic acid

Amphiphilic low molecular weight chitosan-lipoic acid (LC-LA) conjugates with different degrees of substitution (DS) of LA were synthesized by N, N′‑carbonyldiimidazole (CDI) catalysis to self-assemble into redox-sensitive micelles. Critical micelle concentration (CMC), size, zeta potential, biocompatibility and redox-sensitive behavior of blank micelles were investigated. The results indicated that blank micelles with low CMC, nanoscale size and positive zeta potential showed excellent biocompatibility and redox-sensitive behavior. Doxorubicin (Dox) loaded micelles were prepared by encapsulating Dox into blank micelles. The loading ability, trigger-release behavior, antitumor activity and cellular uptake of Dox loaded micelles were studied. The results demonstrated that Dox loaded micelles with superior loading ability exhibited redox-trigger behavior, strong antitumor activity and increased cellular uptake efficiency against A549 cell. Besides, the effect of DS of LA on above properties was estimated. An increase in DS of LA reduced the CMC and cumulative release amount of Dox, but improved the loading efficiency, antitumor activity, and cellular uptake of Dox loaded micelles, which resulted from stronger interaction of hydrophobic groups in micelles with the DS of LA increased. Overall, self-assembled LC-LA micelles with good biosecurity and redox-sensitive behavior hold promising application prospects in Dox delivery and improving cancer therapeutic effect of Dox.

Determination of HER2 binding domain in antigen-antibody complexes based on chemical crosslinking mass spectrometry

Chemical crosslinking (XL) of non-covalent antigen-antibody complexes followed by mass spectrometric identification (MS) of inter-protein crosslinks can provide spatial constraints between relevant residues, which are valuable structural information associated with the molecular binding interface. To highlight the potential of XL/MS in the biopharmaceutical industry, we herein developed and validated an XL/MS workflow that employed a zero-length linker, 1,1′‑carbonyldiimidazole (CDI), and a widely used medium-length linker, disuccinimidyl sulfoxide (DSSO), for fast, accurate determination of antigen domains targeted by therapeutic antibodies. To avoid false identification, system suitability samples and negative samples were designed for all experiments, and all tandem mass spectra were manually examined. To validate the proposed XL/MS workflow, two complexes involving human epidermal growth factor receptor 2 Fc fusion protein (HER2Fc) with known crystal structures, including HER2Fc-pertuzumab and HER2Fc-trastuzumab, have been subjected to CDI and DSSO crosslinking. Crosslinks established by CDI and DSSO between HER2Fc and pertuzumab accurately revealed their interaction interface. CDI crosslinking contributes more than DSSO because of its short spacer arm and high reactivity towards hydroxyl groups, demonstrating its capacity in protein interaction analysis. The correct binding domain cannot be revealed solely based on DSSO in the HER2Fc-trastuzumab complex, because domain proximity revealed by this 7-atom spacer linker cannot be directly translated as binding interfaces. As the first successful XL/MS application in early-stage therapeutic antibody discovery, we analyzed the molecular binding interface between HER2Fc and H-mab, an innovant drug candidate whose paratopes have not been studied yet. We predict that H-mab probably targets HER2 Domain I. The proposed XL/MS workflow can serve as an accurate, fast, and low-cost method to study the interaction between antibodies and large multi-domain antigens. SignificanceThis article described a fast, low-consumption approach based on chemical crosslinking mass spectrometry (XL/MS) using two linkers for binding domain determination in multidomain antigen-antibody complexes. Our results highlighted the higher importance of zero-length crosslinks established by CDI than 7-atom DSSO crosslinks, as residue proximity revealed by zero-length crosslinks is closely related to epitope-paratope interaction surfaces. Furthermore, the higher reactivity of CDI towards hydroxyl groups broadens the ranges of possible crosslinks, despite the necessity of delicate operation in CDI crosslinking. We suggest that all established CDI and DSSO crosslinks should be comprehensively considered for correct binding domain analysis because predictions solely based on DSSO might be ambiguous. We have determined the binding interface in the HER2-H-mab using CDI and DSSO, which is the first successful application of XL/MS in real-world early-stage biopharmaceutical development.

Cytotoxicity and Antibacterial Efficacy of Betaine- and Choline-Substituted Polymers.

Cationic charge has been widely used to increase polymer adsorption and flocculation of dispersions or to provide antimicrobial activity. In this work, cationization of hydroxyethyl cellulose (HEC) and polyvinyl alcohol (PVA) was achieved by covalently coupling betaine hydrochloride and choline chloride to the polymer backbones through carbonyl diimidazole (CDI) activation. Two approaches for activation were investigated. CDI in excess was used to activate the polymers' hydroxyls followed by carbonate formation with choline chloride, or CDI was used to activate betaine hydrochloride, followed by ester formation with the polymers' hydroxyls. The first approach led to a more significant cross-linking of PVA, but not of HEC, and the second approach successfully formed ester bonds. Cationic, nitrogen-bearing materials with varying degrees of substitution were obtained in moderate to high yields. These materials were analyzed by Fourier transform infrared spectroscopy, nuclear magnetic resonance, polyelectrolyte titration, and kaolin flocculation. Their dose-dependent effect on the growth of Staphylococcus aureus and Pseudomonas aeruginosa, and L929 mouse fibroblasts, was investigated. Significant differences were found between the choline- and betaine-containing polymers, and especially, the choline carbonate esters of HEC strongly inhibited the growth of S. aureus in vitro but were also cytotoxic to fibroblasts. Fibroblast cytotoxicity was also observed for betaine esters of PVA but not for those of HEC. The materials could potentially be used as antimicrobial agents for instance by coating surfaces, but more investigations into the interaction between cells and polysaccharides are necessary to clarify why and how bacterial and human cells are inhibited or killed by these derivatives, especially those containing choline.

Research on Deacidification and Reinforcement of Archives Paper with Calcium Carbonate Nanoparticles/Modified Hydroxypropyl Cellulose

The aging process of paper will be accelerated by acidification behavior during the storage process of paper archives, and the mechanical properties of paper archives will be weakened. By deacidizing and strengthening, the further aging of the acidified archives paper can be delayed or prevented, and the mechanical properties can be improved, so that the service life of paper archives is prolonged. To delay even to prevent the aging process, deacidizing and strengthening technology is employed. Herein, the “hybrid” system was reported by combining nano-calcium carbonate as deacidification agent, modified hydroxypropyl cellulose as reinforcement agent and ethanol as dispersant. The artificially acidified paper was brushed with it, and the pH value, mechanical properties and whiteness were measured to study the effect of deacidification and reinforcement. The results showed that oleic acid was successfully grafted onto hydroxypropyl cellulose by N,N′-carbonyl diimidazole mediated method to obtain oleic acid grafted hydroxypropyl cellulose with good dispersion in ethanol. After treating acidified paper with “hybrid” system, the pH value and the tensile strength index increase, the whiteness is almost unchanged, that is, the use of “hybrid” system plays a good deacidifying strengthening effect. The acidified paper samples before and after treatment with “hybrid” system were subjected to dry-heat aging treatment. Compared with acidified paper, the pH value, tensile strength index and whiteness of acidified paper treated with “hybrid” system are effectively inhibited, that is, the use of “hybrid” system can effectively delay the aging and acidification process of paper.

Synthesis and structural characterization of β -cyclodextrin butenate

ABSTRACTβ-cyclodextrin butenate was synthesized by using N, N’-Carbonyldiimidazole (CDI) activating reagent and 4-Dimethylaminopyridine (DMAP) as catalyst. The best preparation condition of β-CD butenate was described as below: reaction temperature was 25°C, concentration of 2-butenoic acid was 450 mmol/L, concentration of DMAP was 12.5 mmol/L and reaction time was 20 minutes and at this condition the yield of β-CD butenate was 0.83 mmol/g. According to the results of FT-IR spectrum, NMR spectroscopy and HPLC-QTof-mass spectrum of β-CD butenate, there were four types β-CD butenate synthesized, which were β-CD-2-butenoic acid monoester, β-CD-2-butenoic acid diester, β-CD-2-butenoic acid triester and β-CD-2-butenoic acid tetraester, respectively.

Design and synthesis optimization of novel diimide indoles derivatives for ameliorating acute lung injury through modulation of NF-κB signaling pathway

Acute lung injury (ALI) is a common respiratory disease caused by local or systemic inflammatory reaction. Based on the natural 7-chain diaryl anti-inflammatory framework, a series of diimide indoles derivatives were designed by combining curcumin and indole in this study. The synthesis of diimide compounds was extended using dichloromethane (DCM) as solvent and 1,1′-carbonyldiimidazole (CDI) and sodium hydride (NaH) as double activators, and a total of 40 diimide-indole derivatives were obtained. The results of in vitro anti-inflammatory activity showed that most compounds could inhibit the production of interleukin-6 (IL-6) better than curcumin and indomethacin. Among the compounds, the IC50 of compound 11f on IL-6 reached 1.05 μM with no obvious cytotoxic side effects. Mechanistically, compound 11f could block the expression of NF-κB P65 phosphorylation, and nuclear translocation of P65. The acute toxicity tests in-vivo also showed no obvious toxicity in mice after the intragastric administration of 1000 mg/kg. In addition, the compound 11f could significantly inhibit the LPS-induced inflammatory response in mice and reduce the number of neutrophils and wet/dry lung weight ratio, thereby alleviating ALI. These results indicated that the novel diimide indoles were promising anti-inflammatory agents for the treatment of ALI.

Use of Carbonyldiimidazole as an Activator of Formic Acid in a Tris(dibenzylideneacetone)dipalladium-Catalyzed Formylation of Aryl Iodides

AbstractA carbonyldiimidazole (CDI)-promoted generation of CO from formic acid has been exploited in a reductive formylation of aryl iodides in the presence of tris(dibenzylideneacetone)dipalladium. The reaction conditions are mild with a broad functional-group tolerance that includes keto, bromo, nitrile, ester, and nitro groups. In the reaction pathway, CDI reacts with formic acid to generate a formyl imidazole that ultimately produces the CO needed for the formylation process on the activated arylpalladium complex.

Facile synthesis of a new covalent organic framework (COF-AYLIN) based on polyamide links and their application in C[sbnd]N coupling reaction

Among the reactions, CN coupling is one of the most important and important reactions that have taken a significant part in the industry. This study defines the design/preparation of an eco-friendly recyclable catalyst for CN coupling reaction. For this target, a new policy was designed to manufacture a new amide-based COF via the reaction amid benzidine and Benzene-1,3,5-tricarboxylic acid (BTC). BTC was activated with carbonyl diimidazole (CDI) and then reacted with benzidine for the synthesis of favorable COF (i.e., COF-AYLIN). Subsequent, the as-prepared COF was decorated via palladium ions to synthesize Pd/COF-AYLIN. The synthesized compounds were identified through the required techniques including N2 isotherms, TEM, EDX FT-IR, XRD, SEM, ICP-OES and TG-DTA. The computer simulation results possess suggested multi sheets of the 2D framework of COF-AYLIN. Consequently, It was found that palladium ions are placed between the layers and on the COF surfaces. This nanocatalyst was used in CN Cross-Coupling reaction and showed its usage in a diverse range of different functional groups with good efficiency. The reason for introducing this catalyst system is because of its advantages such as considerably high selectivity, almost complete conversion of products, good turnover frequency (TOF), high yield, convenient separation of catalyst and product. The results show that the highest efficiency of the product in the reaction was obtained in the shortest possible time with the use of Pd/COF-AYLIN.

Comparison of Synthetic Methods and Identification of Several Artificial Antigens of Deoxynivalenol.

The purpose of this experiment was to study the design and modification of hapten molecules and artificial antigen molecules of deoxynivalenol (DON), and to compare the preparation and identification methods of four artificial antigens. According to the characteristics of the molecular structure of DON, four artificial antigen coupling methods were designed-namely, N,N'-carbonyldiimidazole (CDI), 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC), isobutyl chloroformate (IBCF), and N-hydroxysuccinimide (NHS)-to prepare artificial antigens and detection antigens. Through ultraviolet (UV), infrared (IR), and SDS-polyacrylamide gel electrophoresis (SDS-PAGE), along with other physical and chemical identification methods and animal immunisation, the best artificial antigen coupling method was screened. The results showed that the CDI method achieved the best effect among the synthesis methods. The titre of anti-DON polyclonal antibody (pAb) produced by animal immunisation reached 1: (6.4 × 103). The half inhibitory concentration (IC50) was 47.75 ng/mL, the cross-reaction rate with 3-acetyldeoxynivalenol (3-AcDON) was slightly higher at 35.3%, and there was no cross-reaction with other compounds; therefore, four artificial antigens were successfully prepared by using the molecular structure of DON. Through identification, the CDI method was screened as the best artificial antigen synthesis method, with the highest DON pAb titre, the best sensitivity, and the strongest specificity. This will lay a solid antigenic foundation for the preparation of better anti-DON monoclonal antibodies (mAbs) in the future.

Self-Assembled Redox-Sensitive Polymeric Nanostructures Facilitate the Intracellular Delivery of Paclitaxel for Improved Breast Cancer Therapy.

A two-tier approach has been proposed for targeted and synergistic combination therapy against metastatic breast cancer. First, it comprises the development of a paclitaxel (PX)-loaded redox-sensitive self-assembled micellar system using betulinic acid-disulfide-d-α-tocopheryl poly(ethylene glycol) succinate (BA-Cys-T) through carbonyl diimidazole (CDI) coupling chemistry. Second, hyaluronic acid is anchored to TPGS (HA-Cys-T) chemically through a cystamine spacer to achieve CD44 receptor-mediated targeting. We have established that there is significant synergy between PX and BA with a combination index of 0.27 at a molar ratio of 1:5. An integrated system comprising both BA-Cys-T and HA-Cys-T (PX/BA-Cys-T-HA) exhibited significantly higher uptake than PX/BA-Cys-T, indicating preferential CD44-mediated uptake along with the rapid release of drugs in response to higher glutathione concentrations. Significantly higher apoptosis (42.89%) was observed with PX/BA-Cys-T-HA than those with BA-Cys-T (12.78%) and PX/BA-Cys-T (33.38%). In addition, PX/BA-Cys-T-HA showed remarkable enhancement in the cell cycle arrest, improved depolarization of the mitochondrial membrane potential, and induced excessive generation of ROS when tested in the MDA-MB-231 cell line. An in vivo administration of targeted micelles showed improved pharmacokinetic parameters and significant tumor growth inhibition in 4T1-induced tumor-bearing BALB/c mice. Overall, the study indicates a potential role of PX/BA-Cys-T-HA in achieving both temporal and spatial targeting against metastatic breast cancer.

Zinc Promoted Urea Synthesis Using Carbonyldiimidazole as Carbonyl Source and Its Application for the Synthesis of Cariprazine

AbstractA convenient method has been developed for symmetrical and un‐symmetrical urea synthesis by using Carbonyldiimidazole (CDI) and recyclable activated zinc metal. This reaction is suitable for all types of amines and gives the desired urea products with good to excellent yield. The developed synthetic approach was employed for the synthesis of the Cariprazine drug.

Preparation of nanocellulose grafted molecularly imprinted polymer for selective adsorption Pb(II) and Hg(II)

Heavy metal pollution has become a major problem in environmental pollution. Ion imprinted polymers with specific identification and wide practicality have gradually become an important tool for wastewater treatment. In this work, ion-imprinted polymer-grafted modified nanocellulose was designed as an adsorbent for the serious hazard of Pb(II) and Hg(II) in wastewater. This work used medical cotton wool as raw material to prepare a nanocellulose suspension by acid-catalyzed hydrolysis. The high reactivity of carbonyl diimidazole (CDI) was utilized to react with acrylic acid (AA) to generate reactive intermediates, which then reacted with nanocellulose to form activated nanocellulose (AA-CDI-NC). Crown ether was used as functional monomers to synthesize Pb(II) ion-imprinted polymers and grafted onto the AA-CDI-NC surface (Pb(II)-MIP-NC). Meanwhile, Hg(II) ion-imprinted polymer was synthesized and grafted onto the AA-CDI-NC surface (Hg(II)-MIP-NC) using thymine as a functional monomer. The experimental results showed that Pb(II)-MIP-NC and Hg(II)-MIP-NC could effectively adsorb Pb(II) and Hg(II), respectively. Their adsorption behaviors for Pb(II) and Hg(II) were consistent with the secondary kinetic model and Langmuir adsorption isotherm model. The adsorption capacities of Pb (II)-MIP-NC and Hg (II)-MIP-NC for Pb (II) and Hg (II) were 27.55 mg/g and 161.31, respectively.

1,1'-Carbonyldiimidazole-mediated transformation of allomaltol containing hydrazides into substituted 3-acetyltetronic acids.

For the first time, the reaction of allomaltol containing hydrazides with 1,1'-carbonyldiimidazole (CDI) was studied. It was shown that under the considered conditions, 3-hydroxy-4-pyranone derivatives were transformed into 3-acetyltetronic acids bearing a pyrrolidin-2-one moiety. We have found that the key intermediates of the investigated process are substituted 6-oxa-1-azaspiro[4.5]dec-7-ene-2,9-diones. The structures of one final product and one intermediate were confirmed by X-ray analysis. The disclosed reaction was tested using a wide range of substituted allomaltols with various carboxamide units. It was demonstrated that in the case of hetaryl containing hydrazides and hydroxamic acids, the direction of the process is completely changed and cyclization into substituted pyrano[3,2-b]pyrans occurs.

Facile synthesis of a new covalent organic nanosheet (CON-KEY1) based on polyamide links as an effective heterogeneous catalyst in C-C cross coupling reactions.

C-C coupling reactions represent a fundamental synthetic methodology widely employed in academic and industrial settings. Herein, we present a report on developing and synthesizing a heterogeneous catalyst that is environmentally compatible and has recycling capabilities. Furthermore, the utilization of this catalyst for C-C coupling reactions was explored. A novel amide-based CON was prepared via the reaction of a novel [2,2'-bipyridine]-5,5'-diamine (BDA) and 1,3,5-tris(4-carboxyphenyl) (TCB). TCB was activated with carbonyl diimidazole (CDI) and then reacted with BDA to synthesize favorable CON (i.e., CON-KEY1). Finally, the CON synthesized was reacted with palladium chloride ions, and the palladium-containing organocatalytic complex was decorated with the abbreviated Pd/CON-KEY1. This new heterogeneous complex was fully characterized through the required techniques, including FT-IR, EDX, XRD, TEM, SEM, ICP, TGA-DTA, N2 isotherms, and elemental mapping analysis. Computer simulation results include a multi-sheet 2D framework proposed by CON-KEY1. As a result, palladium ions were found to be arranged between the layers and on the CON surface. This heterogeneous complex functioned as a catalyst precursor in both the Suzuki-Miyaura coupling reaction of aryl boronic acids with aryl halides and the Heck reaction of aryl halides with acrylate derivatives or styrene. The desired coupling products with various functional groups were successfully attained with excellent yields of up to 98%. Simple set-up, improved yields, short reaction times, non-toxic solvents, catalyst durability, and high turnover frequency are among the distinct advantages of this synthetic method. Some other outstanding features of this catalytic system include convenient separation of catalysts and products, high yields, almost complete conversion, high selectivity, and good turnover frequency (TOF). The results show that the highest product efficiency in the reaction was achieved in the shortest possible time using Pd/CON-KEY1. Theoretical studies demonstrated the precedence of the palladium complexation with nitrogen atoms of CON-KEY1 rather than oxygen ones. Natural Bond Orbital (NBO) analysis affirmed that the system with Pd-N bonds (Eg = 0.089 eV) is more reactive with high electron conductivity compared to the Pd-O system (Eg = 0.120 eV).

Ultramicroporous polyureas synthesized with amines and 1,1′-Carbonyldiimidazole and their CO2 adsorption

Microporous polyureas can be highly stable, but isocyanates or phosgene are normally used for the synthesis. Here, it was postulated and demonstrated that 1,1′-carbonyl diimidazole (CDI) could be used for the synthesis. By reacting tetrakis(4-aminophenyl)methane with CDI, a series of new polyureas with ultramicropores (pores <0.7 nm) were synthesized. To tailor thermal properties and porosity, the ratio of tetraamine-to-CDI and the reaction temperature were varied. The CO2 adsorption capacities (with values up to 0.74 mmol/g at 0.15 bar/273 K and 1.91 mmol/g at 1 bar/273 K) were ascribed to the ultramicroporosity. The CO2-based Dubinin-Radushkevich surface areas reached 395 m2/g (at 273 K), while the N2-based BET surface areas (at 77 K) were small. The apparent CO2-over-N2 selectivity was also high for the polymers at 273 K with estimated values of 31–92 for 15/85 v/v mixtures of CO2 and N2. This high selectivity was ascribed to the kinetic hindrance of N2 diffusion. It was noted that one of the polymers changed color irreversibly upon heating. In conclusion, it was shown that CDI and amines could be used to synthesize ultramicroporous polyureas, and that these polymers can exhibit irreversible thermochromism. This thermal effect was attributed to the electron-rich urea moieties, aromatic units, and conjugation.

Development of antioxidant chitosan-based films incorporated with chitooligosaccharide-caffeic acid conjugates

Chitooligosaccharide-caffeic acid (COS-CA) conjugates with three different grafting degrees were synthesized by the N, N′-carbonyldiimidazole (CDI) mediated method and used as functional components to prepare antioxidant chitosan-based composite films. The effects of the synthesized conjugates on the physical and biological properties of chitosan-based films, including mechanical property, UV-barrier property, optical, water vapor permeability, thermal stability, degradation behavior in soil, and antioxidant activity, were investigated. Chitosan acetate films with chitooligosaccharide or without other additives were used as the control. The results showed that the incorporation of COS-CA conjugates caused significant increases in mechanical property, color difference, and UV-barrier property without affecting thermal stability of films and endowed the chitosan-based films with excellent DPPH radical scavenging ability and reducing capacity. Moreover, the grafting ratios of caffeic acid in COS-CA conjugates had a noticeable influence on these changes of chitosan-based composite films. Overall, chitosan/COS-CA conjugates composite films with great UV-barrier property and excellent antioxidant activity could be developed as biodegradable antioxidant biomaterials for food packaging.

Research on N,N′‐carbonyldiimidazole: A novel low‐temperature imidization accelerator of polyimide

AbstractHigh imidization temperature of polyimides (PIs) brings great restriction to the applications in electronic industry. In this study, N,N′‐carbonyldiimidazole (CDI), a novel low‐temperature imidization accelerator with the unique dual function of catalyst and dehydrating agent, was researched to solve this problem. PIs synthesized from 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) and 4,4′‐oxydianiline were researched as the main object on method A and method B, two preparation methods of PIs, by introduction of CDI, which was found that the PIs prepared by method A achieved complete imidization and basically had no residual CDI and N,N‐Dimethylacetamide at 180 °C under vacuum, while the completely imidized PIs prepared by method B were also obtained at 40 °C. Even prepared at low temperature, the PI films with adding CDI both showed satisfactory thermal and mechanical properties, especially in reducing coefficient of thermal expansion. In addition, the universality of the reaction between CDI and poly(amic acid) were also verified by other soluble PI systems. All these results prove the superior performance of CDI in lowering imidization temperature, showing great potentials in low‐temperature cured PIs.