scholarly journals Spontaneous structural transition and crystal formation in minimal supramolecular polymer model

2016 ◽  
Vol 2 (2) ◽  
pp. e1500827 ◽  
Author(s):  
Galit Fichman ◽  
Tom Guterman ◽  
Joshua Damron ◽  
Lihi Adler-Abramovich ◽  
Judith Schmidt ◽  
...  
Keyword(s):  
Structural Transition ◽  
Sol Gel ◽  
Building Blocks ◽  
Supramolecular Polymers ◽  
Supramolecular Polymer ◽  
Crystal Formation ◽  
X Ray Crystallography ◽  
Sol Gel Transition ◽  
Nanoscale Order

The association of building blocks into supramolecular polymers allows the fabrication of diverse functional architectures at the nanoscale. The use of minimal assembly units to explore polymer dynamics and phase transitions significantly contributes to the application of polymer physicochemical paradigms in the field of supramolecular polymers. We present a minimal model that displays spontaneous coordinated structural transitions between micro- and nanostructures, hydrogels with nanoscale order, and single crystals. The simple amphiphilic 9-fluorenylmethoxycarbonyl-3,4-dihydroxyphenylalanine (Fmoc-DOPA) modified amino acid undergoes a noninduced transition from spherical assemblies into nanofibrils followed by sol-gel transition, nanotube formation via intermediate assembly, and crystallization within the gel. Notably, the transition kinetics is slow enough to allow both multistage and multiscale characterization of the supramolecular arrangement using electron microscopy, vibrational and circular dichroism spectroscopies, nuclear magnetic resonance, and x-ray crystallography. This minimalistic system is the first comprehensive model for a complete spontaneous structural transition between diverse states governed by distinct molecular interactions.

Synthesis and characterization of new tetra-substituted porphyrins with exo-donor carboxylic groups as building blocks for supramolecular architectures: Catalytic and structural studies of their metalated derivatives

2010 ◽  
Vol 14 (09) ◽  
pp. 804-814 ◽  
Author(s):  
Lucia Carlucci ◽  
Gianfranco Ciani ◽  
Simona Maggini ◽  
Davide M. Proserpio ◽  
Fabio Ragaini ◽  
...  
Keyword(s):  
Building Blocks ◽  
Supramolecular Organization ◽  
Silver Complexes ◽  
Structural Studies ◽  
Polymeric Compound ◽  
X Ray ◽  
X Ray Crystallography ◽  
Supramolecular Architectures ◽  
Carboxylic Groups

We report herein the synthesis of the porphyrins 5,10,15,20-tetrakis(4-carboxybiphenyl)-porphyrin (H2TCBP) and 5,10,15,20-tetrakis(4-carboxy-2,6-dimethylbiphenyl)porphyrin (H2TCDMBP) bearing diphenyl units on meso-positions, and of their cobalt and silver derivatives. The silver complexes of H2TCDMBP and of H2TCPP ( H2TCPP = 5 ,10,15,20-tetrakis(4-carboxyphenyl)porphyrin) were investigated by X-ray crystallography and their supramolecular organization elucidated. Co(TCBP) was reacted with copper formate, yielding a polymeric compound that showed a catalytic activity in the benzylic amination of hydrocarbons using arylazide as aminating agent.

Rheological characterization of BaTiO3 sol-gel transition

1997 ◽  
Vol 9 (1) ◽  
pp. 5-15 ◽  
Author(s):  
A. Brasseur ◽  
B. Michaux ◽  
R. Pirard ◽  
O. Van Cantfort ◽  
J. P. Pirard ◽  
...  
Keyword(s):  
Sol Gel ◽  
Rheological Characterization ◽  
Sol Gel Transition ◽  
Gel Transition

Synthesis and Characterization of Cellular SiO2 Materials by Foaming Sol Gels

1990 ◽  
Vol 207 ◽  
Author(s):  
Josephine Covino ◽  
Allen P. Gehris
Keyword(s):  
Sol Gel ◽  
Optical Characterization ◽  
Viscosity Change ◽  
Density Measurements ◽  
X Ray ◽  
X Ray Crystallography ◽  
Foaming Process ◽  
Sol Gel Process ◽  
Porous Oxides

AbstractA variety of cellular SiO2 materials have been synthesized using a foaming sol-gel process and their properties have been characterized. The process uses the rapid viscosity change during gelation to stabilize the structure of a foamed silica sol. It was found that the properties of these cellular materials are determined by method used. For example, the porosity and strength of these porous oxides depend on method of agitation and addition of Freon during the foaming process.Density measurements, viscosity measurements as a function of pH, optical characterization, x-ray crystallography, ultimate compressive strength, dielectric constant measurements and thermal diffusivity were used to characterize these porous SiO2 materials. This paper will discuss the synthetic processes used to develop the porous silicas and properties of these materials.

Characterization of the Sol-Gel Transition of Alumina Sols Prepared from Aluminum Alcoxides via 27Al NMR

1986 ◽  
Vol 73 ◽  
Author(s):  
William L. Olson ◽  
Lorenz J. Bauer
Keyword(s):  
Nmr Spectra ◽  
Sol Gel ◽  
27Al Nmr ◽  
Sol Gel Transition ◽  
Hydrolysis Of ◽  
Gel Transition

ABSTRACT27Al NMRsp ectra were obtained on a series of alumina sols prepared by the hydrolysis of aluminum sec-butoxide. Subtle but distinct differences were observed in the solution 27Al NMR spectra of sols which varied in appearance from being very milky to completely transparent. No changes were observed in the 27Al spectra of sols which had been aged. The adddition of sufficient quantities of acid or base to gel the sol precipitated dramatic changes in the Al spectra. Aluminum-27 NMR was found to be a highly useful tool for probing the sol-gel transformation of this system.

Characterization of Magnetic Cellulose Microspheres Reconstituted from Ionic Liquid

2013 ◽  
Vol 634-638 ◽  
pp. 913-917
Author(s):  
Shuai Peng ◽  
Juan Fan ◽  
Jie Chang
Keyword(s):  
Sol Gel ◽  
Vibrating Sample Magnetometer ◽  
Cellulose Dissolution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mean Diameter ◽  
Sol Gel Transition ◽  
Gel Transition ◽  
Structure Properties

Magnetic Fe3O4/cellulose microspheres with mean diameter of 100 μm were prepared by sol-gel transition method using ionic liquids (AmimCl) as solvent for cellulose dissolution and regeneration. Their structure , properties and morphology were analysed using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and vibrating-sample magnetometer. The results indicated that the synthesized microspheres were good sphere with a mean diameter of about 100 μm. It also showed that cellulose had been successfully covered onto the surface of Fe3O4 after the preparation. Therefore, we have provided a simple and biocompatible support for applications in the biomaterials field.

Regioselective Mono and Homo/hetero Dihalogenation of the Benzothioxanthene Monoimide

2020 ◽  
Author(s):  
Clement Dalinot ◽  
Pablo Simon Marques ◽  
Jose Maria Andrés Castán ◽  
Pierre Josse ◽  
Magali Allain ◽  
...  
Keyword(s):  
Building Blocks ◽  
X Ray ◽  
Conjugated Systems ◽  
X Ray Crystallography

Through the preparation and characterization of five new derivatives, the regioselective mono and di, homo and hetero, halogenation of the benzothioxanthene (<b>BTXI</b>) core is demonstrated herein. All structurally solved by X-ray crystallography, these complementary functionalized building blocks open doors to the design of new symmetrical and asymmetrical π-conjugated systems based on this promising but still under-explored rylene.

A Complete Structural and Dynamic Characterization of Supramolecular Polymers via Automatic Learning of Defects

2019 ◽  
Author(s):  
Piero Gasparotto ◽  
Davide Bochicchio ◽  
Michele Ceriotti ◽  
Giovanni M. Pavan
Keyword(s):  
High Resolution ◽  
Self Assembly ◽  
Noncovalent Interactions ◽  
Molecular Simulations ◽  
Machine Learning Techniques ◽  
Supramolecular Polymers ◽  
Structure Stability ◽  
Supramolecular Polymer ◽  
Soft Systems

A central paradigm of self-assembly is to create ordered structures starting from molecular monomers that spontaneously recognize and interact with each other via noncovalent interactions. In the recent years, great efforts have been directed toward reaching the perfection in the design of a variety of supramolecular polymers and materials with different architectures. The resulting structures are often thought of as ideally perfect, defect-free supramolecular fibers, micelles, vesicles, etc., having an intrinsic dynamic character, which are typically studied at the level of statistical ensembles to assess their average properties. However, high-resolution molecular simulations recently demonstrated that local defects that may be present or may form in these assemblies, and which are poorly captured by conventional approaches, are key to controlling their dynamic behavior and properties. The study of these defects poses considerable challenges, as the flexible/dynamic nature of these soft systems makes it difficult to identify what effectively constitutes a defect, and to characterize its stability and evolution. Here, we demonstrate the power of unsupervised machine learning techniques to systematically identify and compare defects in supramolecular polymer variants in different conditions, using as a benchmark high-resolution molecular simulations of a family of supramolecular polymers. We shot that this approach allows a complete data-driven characterization of the internal structure and dynamics of these complex assemblies and of the dynamic pathways for defects formation and resorption. This provides a useful, generally applicable approach to unambiguously identify defects in these dynamic self-assembled materials and to classify them based on their structure, stability and dynamics.

Thermo-Reversible Sol−Gel Transition of Surface Modified Titanium Poly Oxo Building Blocks

2009 ◽  
Vol 114 (3) ◽  
pp. 1416-1423 ◽  
Author(s):  
Renata C. K. Kaminski ◽  
Sandra H. Pulcinelli ◽  
Patrick Judeinstein ◽  
Florian Meneau ◽  
Valérie Briois ◽  
...  
Keyword(s):  
Sol Gel ◽  
Building Blocks ◽  
Sol Gel Transition ◽  
Surface Modified ◽  
Gel Transition

High-Resolution TEM Characterization of Carbon Aerogels as Catalyst Supports

2003 ◽  
Vol 800 ◽  
Author(s):  
Dafei Kang ◽  
Ying Zhang ◽  
Carl Saquing ◽  
Can Erkey ◽  
Mark Aindow
Keyword(s):  
Structural Transition ◽  
Sol Gel ◽  
Thermal Reduction ◽  
Carbon Aerogels ◽  
Catalyst Supports ◽  
High Resolution Tem ◽  
Organometallic Precursors ◽  
Gel Processing

ABSTRACTCarbon aerogels with tailored pore sizes were prepared by using a combination of sol-gel processing, supercritical CO2 extraction and pyrolysis. Ruthenium particles were incorporated via impregnation of organometallic precursors using supercritical CO2, followed by in situ thermal reduction. TEM studies reveal that the carbon aerogels are characterized by a continuous pore structure and that the ruthenium particles are highly dispersed with a narrow size distribution. It is found that under certain circumstances the carbon aerogels undergo a structural transition under the electron beam, in which the original tortuous aerogel network transforms into onion-like structures.

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