Well‐Controlled Biodegradable Nanocomposite Foams: From Microcellular to Nanocellular

Via a batch process in an autoclave, the foam processing of neat polylactide (PLA) and two different types of PLA/layered silicate nanocomposites has been conducted using supercritical carbon dioxide as a foaming agent. The morphological correlation between the dispersed silicate particles with nanometer dimensions in the bulk and the obtained closed‐cell structure of the foam is discussed. This is the first report that deals with the possibility of preparing biodegradable nanocellular polymeric foams via nanocomposite technology.

SEM image of the freeze‐fracture surface of a PLA/layered silicate foam, exhibiting closed‐cell structure.     

Mechanical property and biodegradability of solution‐cast films prepared from amphiphilic polylactide‐grafted dextran

Polylactide (PLA)‐grafted dextran was synthesized with a trimethylsilyl protection method to produce novel biodegradable, biomedical materials. PLA‐grafted dextrans with various lengths and numbers of graft chains were synthesized. The properties of solution‐cast films prepared from PLA‐grafted dextrans were investigated with thermal and dynamic mechanical analyses. The graft‐copolymer films exhibited lower glass‐transition temperatures, melting temperatures (T_m's), and crystallinities as well as higher viscosity properties as compared with poly‐L ‐lactide film. The T_m and crystallinity and mechanical properties at 37 °C could be adjusted by controlling the molecular structure such as the lengths and numbers of graft chains. Furthermore, the biodegradability of PLA‐grafted dextran films was investigated through the weight change of film and the molecular weight change of polymer during the in vitro degradation test. PLA‐grafted dextrans exhibited different degradation behavior from poly‐L ‐lactide with the introduction of a polysaccharide segment and branched structure as well as the change of end‐functional group. The degradation rate of PLA‐grafted dextran and the cast film prepared from PLA‐grafted dextran could be adjusted by controlling the sugar content or the length of graft chains. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 2462–2468, 2003     

Microcellular foaming of polylactide and poly(butylene adipate‐co‐terphathalate) blends and their CaCO3 reinforced nanocomposites using supercritical carbon dioxide

Foamed polylactide (PLA), PLA–PBAT (poly (butylene adipate‐co‐terphathalate)) blend and their composites with CaCO₃ were prepared in a batch process using supercritical carbon dioxide (CO₂) at 12 MPa and 45°C. The solubility of CO₂ and its diffusion patterns in different PLA samples was investigated. PLA systems had a relatively high CO₂ solubility related to the carboxyl groups. CO₂ desorption behaviors in PLA systems first followed the Fickian diffusion mechanism in short time and then decreased slowly to a plateau. The addition of both PBAT and CaCO₃ into PLA impeded the desorption of CO₂. In the presence of second phase PBAT, nanoparticles CaCO₃ and dissolved CO₂, the PLA crystallization behavior investigated by DSC technique was greatly changed. As the desorption time increased, the gas induced crystallinity slightly decreased in consequence of less CO₂ content in each system and thus less plasticization effect. The cell morphology of foamed PLA and PLA composites showed interesting microstructure patterns. The prepared pure PLA foam exhibits a typical bimodal structure because of the foaming in both the amorphous and crystalline zones. With PBAT and CaCO₃ into PLA, the composite foam presented significant increase in cell uniformity and cell density. With less CO₂ content in each PLA sample, the cell structure showed interesting variation. Pure PLA foam presented transition from bimodal structure to more uniform cell structure with decreased cell density. In contract, PLA–PBAT foam show unfoamed regions because of none CO₂ left in the separated PBAT phase. Copyright © 2016 John Wiley & Sons, Ltd.     

Preparation of porous polylactide microspheres by emulsion‐solvent evaporation based on solution induced phase separation

Porous polylactide (PLA) microspheres were fabricated by an emulsion‐solvent evaporation method based on solution induced phase separation. Scanning electron microscopy (SEM) observations confirmed the porous structure of the microspheres with good connectivity. The pore size was in the range of decade micrometers. Besides large cavities as similarly existed on non‐porous microspheres, small pores were found on surfaces of the porous microspheres. The apparent density of the porous microspheres was much smaller than that of non‐porous microspheres. Fabrication conditions such as stirring rate, good solvent/non‐solvent ratio, PLA concentration and dispersant (polyvinyl alcohol, PVA) concentration had an important influence on both the particle size and size distribution and the pore size within the microspheres. A larger pore size was achieved at a slower stirring rate, lower good solvent/non‐solvent ratio or lower PLA concentration due to longer coalescence time. Copyright © 2005 John Wiley & Sons, Ltd.     

Effect of the position of a methoxy substituent on the antimicrobial activity and crystal structures of 4‐methyl‐1,6‐diphenylpyrimidine‐2(1H)‐selenone derivatives

Derivatives of pyrimidine‐2(1H)‐selenone are a group of compounds with very strong antimicrobial activity. In order to study the effect of the position of the methoxy substituent on biological activity, molecular geometry and intermolecular interactions in the crystal, three derivatives were prepared and evaluated with respect to their antimicrobial activities, and their crystal structures were determined by X‐ray diffraction. The investigated compounds, namely, 1‐(X‐methoxyphenyl)‐4‐methyl‐6‐phenylpyrimidine‐2(1H)‐selenones (X = 2, 3 and 4 for 1 , 2 and 3 , respectively), C₁₈H₁₆N₂OSe, showed very strong activity against selected strains of Gram‐positive bacteria and fungi. Two compounds, 1 and 2 , crystallize in the monoclinic space group P2₁/c, while 3 crystallizes in the space group P2₁/n; 1 has two molecules in the asymmetric unit and the other two ( 2 and 3 ) have one molecule. The geometries of the investigated compounds differ slightly in the mutual orientations of the aromatic and pyrimidineselenone rings. The O atom in 1 stabilizes the conformation of the molecules via intramolecular C—H…O hydrogen bonding. The packing of molecules is determined by weak C—H…N and C—H…Se intermolecular interactions and additionally in 1 and 2 by C—H…O intermolecular interactions. The introduction of the methoxy substituent results in greater selectivity of the investigated compounds.     

Influence of chain microstructure on the hydrolytic degradation of copolymers from 1,3‐trimethylene carbonate and L‐lactide

Ring‐opening copolymerization of L ‐lactide (LLA) and 1,3‐trimethylene carbonate (TMC) blends with LLA/TMC feed ratios from 90/10 to 50/50 was realized at 110 or at 180 °C for various time periods, using low toxic zirconium (IV) acetylacetonate (Zr(Acac)₄) as initiator. The resulting copolymers exhibit different chain microstructures. Copolymers obtained at 110 °C exhibit a gradient chain structure with the presence of lactidyl sequences next to very short ones, and are semicrystalline. In contrast, copolymers obtained at 180 °C are amorphous because of a more random chain microstructure with the presence of larger amounts of medium sequences. Degradation of the copolymers was carried out in pH 7.4 phosphate buffer at 37 °C. Analytical techniques such as ¹H NMR, DSC, GPC, and XRD were used to monitor the degradation. Initially amorphous copolymers can remain amorphous during degradation because of the highly random unit's distribution, and equivalent LLA and TMC contents. However, initially amorphous copolymers containing larger amounts of lactidyl units are able to crystallize during degradation because of the presence of relatively long LLA blocks. Insofar, as initially semicrystalline copolymers are concerned, degradation occurs preferentially in the amorphous zones. Therefore, various degradation behaviors and degradation rates can be obtained by varying the chemical composition, chain microstructure, and morphology of PLLA‐PTMC copolymers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3869–3879, 2009     

Novel antimicrobial polyethylene composites prepared by metallocenic in situ polymerization with TiO2‐based nanoparticles

Polyethylene (PE) composites with titanium oxide (TiO₂) nanoparticles were produced via in situ polymerization representing a novel route to obtain antimicrobial polymeric materials. The TiO₂ nanoparticles synthesized by the sol–gel method were used either as‐synthesized or modified organically with hexadecyltrimethoxysilane (Mod‐TiO₂). These particles were added, together with the catalytic system (formed by a metallocenic catalyst and methylaluminoxane as cocatalyst), directly to the reactor, yielding in situ PE composites with 2 and 8 wt % content of nanofiller. The catalytic polymerization activity presented a slight decrease with the incorporation of the TiO₂ and Mod‐TiO₂ nanoparticles compared to polymerization without filler. Regarding the properties of the composites, crystallinity increased slightly when the different nanofillers were added, and the elastic modulus increased around 15% compared to neat PE. PE/TiO₂ nanocomposites containing 8 wt % of TiO₂ exposed to UVA irradiations presented antimicrobial activity against Escherichia coli. The PE/Mod‐TiO₂ nanocomposite with 8 wt % filler killed 99.99% of E. coli, regardless of light and time irradiation. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012     

Triclosan‐based antibacterial paper reinforced with nano‐montmorillonite: a model nanocomposite for the development of new active packaging

In this study, a suitable method is reported to produce reinforced antibacterial paper packaging using the antimicrobial triclosan (TC) and organically modified montmorillonite (OMMT) as “model” compounds. Direct incorporation of TC at a concentration of 1 wt% and OMMT at concentrations of 1, 4, 7, and 10 wt% into papers was performed via coating process, and the resulting materials were characterized by in vitro antimicrobial assays, thermogravimetric analysis, scanning electron microscopy, mechanical tests, and water vapor transmission rate determinations. It was demonstrated that the presence of 1% TC in the coated papers exhibited inhibitory effects against Staphylococcus aureus and Escherichia coli. It was also pointed out that increases of approximately 30% in the tensile strength of commercial paper are obtained by using the OMMT at a concentration of 1 wt%. Water barrier property and thermal stability of paper were also enhanced because of the coating process and the incorporation of OMMT. The results from this study demonstrate that OMMT has a great potential to be incorporated into coating formulations to obtain antibacterial‐coated papers with improved properties for various packaging applications. Copyright © 2011 John Wiley & Sons, Ltd.     

Novel antibacterial fibers of amphiphilic N‐halamine polymer prepared by electrospinning

As a significant role in subcategory of halogen antibacterial field, amphiphilic N‐halamine polymers show a promise as potential antimicrobials having a broad spectrum of microorganisms, long‐term stability, and renewal of their antibacterial properties. By controlling the process parameters, electrospinning has been well recognized as a versatile and effective method being capable of making fibers and could be easily engineered with desired pore size and porosity to enhance the antimicrobial properties. The amphiphilic N‐halamine P (ADMH‐MMA‐HEMA) terpolymer fibers showed efficient antimicrobial properties against both Gram‐positive and Gram‐negative bacteria within brief contact time. The result meant that the polymer fibers of macromolecular architecture with control of structural parameters such as hydrophobicity/hydrophilicity balance achievement improved antimicrobial activities via electrospinning technique. In vitro cytotoxicity study demonstrated that the polymer was biocompatible. As a result, the integration of amphiphilic antibacterial materials and the electrospinning technique provided us a feasible method to fabricate biocompatible antimicrobial products easily with low manufacturing cost and would be applied in many promising application areas.     

Cobalt Carbonate Hydroxide Nanowire Array on Ti Mesh: An Efficient and Robust 3D Catalyst for On‐Demand Hydrogen Generation from Alkaline NaBH4 Solution

In this work, for the first time, a cobalt carbonate hydroxide (Co(CO₃)_0.5(OH)?0.11 H₂O) nanowire array on Ti mesh (CHNA/Ti) was applied to drive the dehydrogenation of alkaline NaBH₄ solution for on‐demand hydrogen production. Compared with other nanostructured Co‐based catalyst systems, CHNA/Ti can be activated more quickly and separated easily from fuel solutions. This self‐supported cobalt salt nanowire array catalyst works as an efficient and robust 3D catalyst for the hydrolysis reaction of NaBH₄ with a hydrogen generation rate of 4000 mL min^?1 g_Co^?1 and a low apparent activation energy of 39.78 kJ mol^?1 and offers an attractive system for on‐demand hydrogen generation.     

Three new quinuclidine‐based structures: second harmonic generation response for 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride

The crystal structures of three quinuclidine‐based compounds, namely (1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine monohydrate, C₇H₁₃N₃·H₂O ( 1 ), 1,2‐bis(1‐azabicyclo[2.2.2]octan‐3‐ylidene)hydrazine, C₁₄H₂₂N₄ ( 2 ), and 1,2‐bis(1‐azoniabicyclo[2.2.2]octan‐3‐ylidene)hydrazine dichloride, C₁₄H₂₄N₄²⁺·2Cl^? ( 3 ), are reported. In the crystal structure of 1 , the quinuclidine‐substituted hydrazine and water molecules are linked through N—H…O and O—H…N hydrogen bonds, forming a two‐dimensional array. The compound crystallizes in the centrosymmetric space group P2₁/c. Compound 2 was refined in the space group Pccn and exhibits no hydrogen bonding. However, its hydrochloride form 3 crystallizes in the noncentrosymmetric space group Pc. It shows a three‐dimensional network structure via intermolecular hydrogen bonding (N—H…C and N/C—H…Cl). Compound 3 , with its acentric structure, shows strong second harmonic activity.     

Comparison of the structure of (E)‐2‐(2‐benzylidenehydrazinylidene)quinoxaline with those of its chloro‐ and bromobenzylidene analogues

(E)‐2‐(2‐Benzylidenehydrazinylidene)quinoxaline, C₁₅H₁₂N₄, crystallized with two molecules in the asymmetric unit. The structures of six halogen derivatives of this compound were also investigated: (E)‐2‐[2‐(2‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(3‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(4‐chlorobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁ClN₄; (E)‐2‐[2‐(2‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(3‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄; (E)‐2‐[2‐(4‐bromobenzylidene)hydrazinylidene]quinoxaline, C₁₅H₁₁BrN₄. The 3‐Cl and 3‐Br compounds are isomorphous, as are the 4‐Cl and 4‐Br compounds. In all of these compounds, it was found that the supramolecular structures are governed by similar predominant patterns, viz. strong intermolecular N—H...N(pyrazine) hydrogen bonds supplemented by weak C—H...N(pyrazine) hydrogen‐bond interactions in the 2‐ and 3‐halo compounds and by C—H...Cl/Br interactions in the 4‐halo compounds. In all compounds, there are π–π stacking interactions.     

PEGDA‐based luminescent polymers prepared by frontal polymerization

Frontal polymerization (FP) of poly(ethylene glycol) diacrylate (PEGDA) was carried out using benzoyl peroxide (BPO) as radical initiator. In addition, a pyrene containing monomer, 1‐pyrenebutyl acrylate (PyBuAc), was incorporated as a fluorescent probe in order to obtain luminescent materials with different chromophore contents. The resulting polymers were characterized by FT‐IR spectroscopy in the solid state and their thermal properties were determined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Moreover, the optical properties of these materials were studied by absorption and fluorescence spectroscopy. The maximum amount of the incorporated pyrene‐containing monomer into the polymer matrix was limited to 1 wt % by the polymerization process. The obtained labeled polymers poly(PEGDA‐co‐PyBuAc) exhibited a broad absorption band at 345 nm. The fluorescence spectra of these polymers exhibited mainly “monomer emission” so that no excimer emission was observed. It is possible to tune the color of the emitted light by varying the pyrene content in the samples. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2890–2897     

Synthesis,Crystal Structure,Spectroscopic, Electrochemical and Antimicrobial Properties of Cu(II) Complex with the Mixed Ligands of 2,9‐Dimethyl‐1,10‐phenanthroline and 4‐Hydroxypyridine‐2,6‐dicarboxylic Acid

A mononuclear Cu(II) complex with mixed ligands, formulated as [Cu(hypydc)(dmp)]·H₂O (hypydc=4‐hydroxypyridine‐2,6‐dicarboxylate, dmp=2,9‐dimethyl‐1,10‐phenanthroline), was synthesized and well characterized by single crystal X‐ray diffraction analysis, as well as spectroscopic (IR, UV‐Vis), and electrochemical methods. The Cu(II) atom exhibits a distorted square‐pyramidal geometry. Intermolecular O? H···O and C? H···O hydrogen bonds, π‐π stacking interactions and C? H···π interactions seem to be effective in the stabilization of the crystal structure. The complex was also evaluated for its antimicrobial activity using in vitro microdilution methods. Six standard bacteria and a strain of Candida albicans were used for the antimicrobial activities. There was a very strong activity against Candida albicans and significant activities against Enterococcus fecalis, Listeria monocytogenes, Bacillus cereus and Staphylococcus aureus, indicating important biological activities of the complex.     

Neutral 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide and its salt forms with inorganic anions

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4‐phenyl‐1‐[phenyl(pyridin‐2‐yl)methylidene]semicarbazide, C₁₉H₁₆N₄O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C₁₉H₁₇N₄O⁺·Cl^?·2H₂O, (II), the nitrate dihydrate, C₁₉H₁₇N₄O⁺·NO₃^?·2H₂O, (III), and the thiocyanate 2.5‐hydrate, C₁₉H₁₇N₄O⁺·SCN^?·2.5H₂O, (IV), of 2‐[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H₂BzPyS]⁺·X^?·nH₂O, with X = Cl^? and n = 2 for (II), X = NO₃^? and n = 2 for (III), and X = SCN^? and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter‐ions (chloride or nitrate) are involved in the formation of a two‐dimensional arrangement by the establishment of hydrogen bonds with the N—H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π–π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H₂BzPyS]⁺ cation is in good agreement with the experimental results.     

[1‐(Pyrazin‐2‐yl)ethylidene]hydrazine: a new multitopic ligand for the design of hybrid molecular frameworks

Hydrazones and their derivatives are closely related to imine compounds and are potential antimicrobial agents. They have also found application in supramolecular chemistry as multitopic ligands to link multiple metal centres for the design of hybrid molecular frameworks. The molecule of the title compound, C₆H₈N₄, consists of an imine linkage with an N—N bond length of 1.3540 (14) Å. This asymmetric compound is nearly planar and adopts an E configuration about the azomethine C=N double bond. In the solid state, there are two intermolecular N—H…N interactions that interconnect the molecules into a two‐dimensional network. The three‐dimensional arrangement of the crystal packing is further stabilized by intermolecular π–π interactions interconnecting the centroids of the heterocyclic rings.     

Biodegradable poly(trimethylene carbonate‐b‐(L‐lactide‐ran‐glycolide)) terpolymers with tailored molecular structure and advanced performance

The macroinitiator of poly(1,3‐trimethylene carbonate) (PTMC) with number‐average molecular weight ( ) of 9.6 × 10³ g mol⁻¹ was synthesized by ring‐opening polymerization at 120°C. Then, the novel terpolymer P(TMC‐b‐(LLA‐ran‐GA)) consisting of PTMC homopolymer segment attached with various monomer molar ratios of L‐lactide (LLA) and glycolide (GA) random copolymerization block was prepared with about 5.0 × 10⁴ g mol⁻¹ by ring‐opening polymerization in bulk at 140°C. The tailored molecular structures of P(TMC‐b‐(LLA‐ran‐GA)) were characterized by ¹H nuclear magnetic resonance, ¹³C NMR, FTIR, and gel permeation chromatography, and chain microstructure analysis was performed in detail with ¹³C NMR spectroscopy. The effect of GA units on the thermal and crystallization behaviors, mechanical properties, as well as biodegradability of terpolymers was investigated by differential scanning calorimetry, wide‐angle X‐ray diffraction, stress‐strain measurements, and in vitro tests in comparison with corresponding poly(trimethylene carbonate‐block‐L‐lactide) copolymer P(TMC‐b‐LLA). The results show that amorphous PTMC segments have a significant effect on condensed state behavior of the terpolymers, and the incorporation of GA units strongly decreases the crystallinity and crystallization ability of LLA segment within terpolymers because of more random LLA‐GA sequence and shorter average LLA block length. Meanwhile, the toughness of materials is greatly improved, and in vitro degradation is also accelerated. Peripheral vascular stents were 3D printed for the first time and met the requirements for application. The results show totally biodegradable terpolymers with unique molecular structure, and modifiable properties are promising new biomaterials with advanced performance for biomedical application.     

Preparation of hollow composite spheres with raspberry‐like structure based on hydrogen‐bonding interaction

The hollow composite spheres with a raspberry‐like structure were prepared by a self‐assemble heterocoagulation based on the inter‐particle hydrogen‐bonding interaction between the amide groups of hollow poly (N,N′‐methylenebisacrylamide‐co‐N‐isopropyl acrylamide) (P(MBA‐co‐NIPAAm)) microspheres and the carboxylic acid groups of poly(ethyleneglycol dimethacrylate‐co‐methacrylic acid) (P(EGDMA‐co‐MAA)) nanoparticles, in which P(EGDMA‐co‐MAA) nanoparticle acted as the corona and the hollow P(MBA‐co‐NIPAAm) microsphere behaved as the core. The control coverage of the corona particles on the surface of hollow core microspheres of P(MBA‐co‐NIPAAm)/P(EGDMA‐co‐MAA) hollow composite sphere was studied in detail through adjustment of the mass ratio between the core and corona particles. The effect of the pH on the stability of the raspberry‐like hollow spheres was investigated. The polymer particles and the resultant heterocoagulated raspberry‐like hollow spheres were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Copyright © 2008 John Wiley & Sons, Ltd.     

Preparation of antibacterial cellulose with a monochloro‐s‐triazine‐based N‐halamine biocide

A novel monochloro‐s‐triazine‐based N‐halamine precursor, 4‐(4‐(5,5‐dimethylhydantoin‐3‐ethylamino)‐6‐chloro‐1,3,5‐triazinylamino)‐benzenesulfonate (HB), was synthesized and characterized by proton nuclear magnetic resonance. The reactive dyes dyeing method was applied to bond HB onto cotton fabrics, and the treated fabrics were confirmed by Fourier transform infrared spectrometer and scanning electron microscope. The chlorinated HB‐treated fabrics showed excellent antibacterial efficacies against Staphylococcus aureus and Escherichia coli O157:H7 and inactivated all inoculated bacteria within 1 min of contact. Interestingly, it was found that the finishing process and following chlorination caused smaller tensile strength loss of cotton fabrics than the traditional pad‐dry‐cure method. Furthermore, the antimicrobial cotton fabrics exhibited good stability and regenerability. Copyright © 2015 John Wiley & Sons, Ltd.     

Two different products from the reaction of 1‐aryl‐5‐chloro‐3‐methyl‐1H‐pyrazole‐4‐carbaldehyde with cyclohexylamine when the aryl substituent is phenyl or pyridin‐2‐yl: hydrogen‐bonded sheets versus dimers

Cyclohexylamine reacts with 5‐chloro‐3‐methyl‐1‐(pyridin‐2‐yl)‐1H‐pyrazole‐4‐carbaldehyde to give 5‐cyclohexylamino‐3‐methyl‐1‐(pyridin‐2‐yl)‐1H‐pyrazole‐4‐carbaldehyde, C₁₆H₂₀N₄O, (I), formed by nucleophilic substitution, but with 5‐chloro‐3‐methyl‐1‐phenyl‐1H‐pyrazole‐4‐carbaldehyde the product is (Z)‐4‐[(cyclohexylamino)methylidene]‐3‐methyl‐1‐phenyl‐1H‐pyrazol‐5(4H)‐one, C₁₇H₂₁N₃O, (II), formed by condensation followed by hydrolysis. Compound (II) crystallizes with Z′ = 2, and in one of the two independent molecular types the cyclohexylamine unit is disordered over two sets of atomic sites having occupancies of 0.65 (3) and 0.35 (3). The vinylogous amide portion in each compound shows evidence of electronic polarization, such that in each the O atom carries a partial negative charge and the N atom of the cyclohexylamine portion carries a partial positive charge. The molecules of (I) contain an intramolecular N—H...N hydrogen bond, and they are linked by C—H...O hydrogen bonds to form sheets. Each of the two independent molecules of (II) contains an intramolecular N—H...O hydrogen bond and each molecular type forms a centrosymmetric dimer containing one R₂²(4) ring and two inversion‐related S(6) rings.