Self‐Assembly of <i>n</i>‐Alkyl‐ and Aryl‐Side Chain Ureas and Their Derivatives as Evidenced by SEM and X‐ray Analysis

Kulikov, Oleg V.; Siriwardane, Dumindika A.; McCandless, Gregory T.; Barnes, Charles L.; Sevryugina, Yulia; DeSousa, Joseph D.; Wu, Jingbo; Sommer, Roger D.; Novak, Bruce M.

doi:10.1002/ejoc.201501242

Cited by 11 publications

(3 citation statements)

References 62 publications

(28 reference statements)

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“…The observed porous domains are believed to be associated with the crystallizing of individual fibers but also may be due to surface dewetting phenomena similar to our previous reports. 33 In toluene, densely packed, thin nanofiber morphologies were observed for both the linear Poly-1 and star Poly-2.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

et al. 2017

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Using the core-first growth strategy, we have synthesized a tris-Ni(II) initiator which bears three initiating sites for the ensuing polymerization of N-1-phenethyl-N′-methylcarbodiimide. The arms of these star polymers bearing chiral side chains adopt single-handed helical rod-like conformations. The polymerization occurs in a controlled, living fashion, and this multiarm architecture imparts a new set of intriguing properties including their self-assembly into diverse nanostructures when cast from different solvents. These assemblies, characterized by AFM, TEM, and DLS, include the formation of nanofiber networks and twisted superhelical nanostructures. Interestingly, by processing these polymers via electrospraying method, hollow and uniform platelet-like particles were obtained. These solvent-dependent morphologies of microparticles were observed by using SEM. The kinetic studies of polymerizations, inspection of self-aggregation behaviors, and electrosprayed architectures will open up possibilities for a variety of potential biomedical applications.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

et al. 2017

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“…Here, we focused on conformationally flexible trisubstituted bis-ureas (TBU) as model compounds (Figure ). This class of molecules has been the subject of several investigations, including crystal engineering studies regarding their self-assembly interactions and competing synthons, − the incorporation of bis-ureas guests in thermoplastic elastomers, and their gelation ability. − In most cases, N , N′ -disubstituted ureas were used, which were generally associated with strongly bifurcated hydrogen bonds (NH···OC interactions).…”

Section: Introductionmentioning

confidence: 99%

Persistence of N—H···O═C Interactions in the Crystallization Mechanisms of Trisubstituted Bis-Ureas with Bulky Substituents

Lopes

Orlando

Simões

et al. 2021

Crystal Growth & Design

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Bis-ureas are generally associated with strongly bifurcated hydrogen bonds (NH···OC interactions). For this reason, a series of trisubstituted bis-ureas (TBU) with bulk substituents were designed and used as a study model to gain a better understanding of the persistence of NH···OC interactions as driving interactions of the crystallization process. The TBU molecules possess different substituents (isopropyl, benzyl, and 4-nitro-benzyl) and variations in the methylene spacer. The TBU self-assembly, through crystallization mechanism proposals, is discussed related to the role of intermolecular interactions that drive and participate in the crystallization process. The intermolecular interactions present in the proposed first nuclei of crystallization were studied by concentration-dependent 1H NMR experiments and QTAIM analysis. Our findings showed that even with bulky substituents, the NH···OC interactions in most compounds played an important role in stabilizing the first nuclei formed during the crystallization process. However, in one case the molecular topology prevented the formation of NH···OC as the driving interaction in the first crystallization nuclei. In this case, the crystallization was mainly governed by a set of “weaker” interactions, showing that a subtle molecular change in the methylene spacer favored H···H interactions over directional N–H···O interactions. For some of the compounds studied, we propose both when the symmetry-independent molecules observed in the crystal lattice could be formed and when the water molecules are probably trapped during the crystallization to form the hydrate crystalline phases. This study contributes to the better understanding of issues related to modulating NH···OC hydrogen bonds using bulky substituents in the self-assembly of flexible TBU molecules.

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“…The C7N1···N1′C7′ dihedral angle for ( S ph )- 5 in the crystal (+77.5°) was slightly different from the DFT-optimized structure (Table S1). Of note, although the NCN angles of various carbodiimides are known as nonlinear (∼170°), , that for the crystalline 5 is almost linear (179.6°). This finding proposed the usefulness of conformational restraints for regulating not only the carbodiimide chirality but also the NCN angle.…”

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confidence: 99%

Preparation of Carbodiimides with One-Handed Axial Chirality

Taniguchi¹,

Suzuki²,

Satoh³

et al. 2018

J. Am. Chem. Soc.

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The axial chirality of carbodiimide was proposed in 1932, but the synthesis of carbodiimide with one-handed axial chirality has not been achieved because of the low barrier of racemization. This work presents a strategy to use a conformationally restrained cyclic structure for creating carbodiimides whose biases of the axial chirality (labeled as S NCN /R NCN ) are higher than 100:1, as determined by vibrational circular dichroism spectroscopy and density functional theory calculations.

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Self‐Assembly of n‐Alkyl‐ and Aryl‐Side Chain Ureas and Their Derivatives as Evidenced by SEM and X‐ray Analysis

Cited by 11 publications

References 62 publications

Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

Rigid, Helical Arm Stars through Living Nickel Polymerization of Carbodiimides

Persistence of N—H···O═C Interactions in the Crystallization Mechanisms of Trisubstituted Bis-Ureas with Bulky Substituents

Preparation of Carbodiimides with One-Handed Axial Chirality

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