Conformational changes in the heat-induced crystallization of poly(2-isopropyl-2-oxazoline) in the solid state

2015 ◽  
Vol 17 (46) ◽  
pp. 31084-31092 ◽  
Author(s):  
Shengtong Sun ◽  
Peiyi Wu
Keyword(s):  
Solid State ◽  
Correlation Analysis ◽  
Vibrational Spectroscopy ◽  
Conformational Changes ◽  
Crystallization Process ◽  
Side Chains ◽  
Two Dimensional ◽  
Induced Crystallization

The dynamic solid-state crystallization process of poly(2-isopropyl-2-oxazoline) was studied by vibrational spectroscopy in combination with two-dimensional correlation analysis, and is shown to be mainly achieved by the lateral distortion of coplanar side chains together with the torsion of the backbone through C–N linkages.

Microdynamic changes of moisture-induced crystallization of amorphous calcium carbonate revealed via in situ FTIR spectroscopy

2019 ◽  
Vol 21 (39) ◽  
pp. 21882-21889 ◽  
Author(s):  
Meng Cheng ◽  
Shengtong Sun ◽  
Peiyi Wu
Keyword(s):  
Calcium Carbonate ◽  
Correlation Analysis ◽  
Ftir Spectroscopy ◽  
Two Dimensional ◽  
In Situ Ftir ◽  
Amorphous Calcium Carbonate ◽  
In Situ Ftir Spectroscopy ◽  
Induced Crystallization

A microdynamic mechanism of moisture-induced ACC crystallization involving three consecutive conversion stages is elucidated via in situ FTIR spectroscopy and two-dimensional correlation analysis.

X-ray Structure Refinement and Vibrational Spectroscopy of Ca8Gd2 (PO4)6 O2

2013 ◽  
Vol 12 (10) ◽  
pp. 719-726
Author(s):  
R. Ayadi ◽  
Mohamed Boujelbene ◽  
T. Mhiri
Keyword(s):  
Solid State ◽  
General Formula ◽  
Vibrational Spectroscopy ◽  
Powder Diffraction ◽  
Infrared Spectra ◽  
Solid State Reaction ◽  
Structure Refinement ◽  
Unit Cell ◽  
Cell Group ◽  
X Ray

The present paper is interested in the study of compounds from the apatite family with the general formula Ca10 (PO4)6A2. It particularly brings to light the exploitation of the distinctive stereochemistries of two Ca positions in apatite. In fact, Gd-Bearing oxyapatiteCa8 Gd2 (PO4)6O2 has been synthesized by solid state reaction and characterized by X-ray powder diffraction. The site occupancies of substituents is0.3333 in Gd and 0.3333 for Ca in the Ca(1) position and 0. 5 for Gd in the Ca (2) position.  Besides, the observed frequencies in the Raman and infrared spectra were explained and discussed on the basis of unit-cell group analyses.

Pathway Complexity in the Stacking of Imine-linked Macrocycles Related to Two-Dimensional Covalent Organic Frameworks

2019 ◽  
Author(s):  
Shiwei Wang ◽  
Anton Chavez ◽  
Simil Thomas ◽  
Hong Li ◽  
Nathan C. Flanders ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Structural Similarity ◽  
Discrete Models ◽  
Side Chains ◽  
Two Dimensional ◽  
Assembly Process ◽  
Covalent Organic Frameworks ◽  
Electron Systems ◽  
Monomer Structure ◽  
Kinetic Traps

This work reports on the assembly of imine-linked macrocycles that serve as models of two-dimensional covalent organic frameworks (2D COFs). Interlayer interactions play an important role in the formation of 2D COFs, yet the effect of monomer structure on COF formation, crystallinity, and susceptibility to exfoliation are not well understood. For example, monomers with both electron-rich and electron-poor π-electron systems have been proposed to strengthen interlayer inter-actions and improve crystallinity. Here we probe these effects by studying the stacking behavior of imine-linked macrocycles that represent discrete models of 2D COFs. <div><br></div><div>Specifically, macrocycles based on terephthaldehyde (PDA) or 2,5-dimethoxyterephthaldehyde (DMPDA) stack upon cooling molecularly dissolved solutions. Both macrocycles assemble cooperatively with similar ΔHe values of -97 kJ/mol and -101 kJ/mol, respectively, although the DMPDA macrocycle assembly process showed a more straightforward temperature dependence. Circular dichroism spectroscopy performed on macrocycles bearing chiral side chains revealed a helix reversion process for the PDA macrocycles that was not observed for the DMPDA macrocycles. <br></div><div><br></div><div>Given the structural similarity of these monomers, these findings demonstrate that the stacking processes associated with nanotubes derived from these macrocycles, as well as for the corresponding COFs, are complex and susceptible to kinetic traps, casting doubt on the relevance of thermodynamic arguments for improving materials quality. <br></div>

Infrared spectra of N-acetyl-L-α-amino-acid N'-methylamides with aliphatic side chains in non-polar solvents

1981 ◽  
Vol 46 (3) ◽  
pp. 772-780 ◽  
Author(s):  
Jorga Smolíková ◽  
Jan Pospíšek ◽  
Karel Bláha
Keyword(s):  
Amino Acid ◽  
Conformational Changes ◽  
Infrared Spectra ◽  
Room Temperature ◽  
Side Chains ◽  
Polar Solvents

Infrared spectra of the L-alanine (I), L-leucine (II), L-valine (III) and L-tert-leucine (IV) N-acetyl N'-methylamides were measured. Amides I-IV are not self associated in tetrachlormethane in the concentration 2 . 10-5 mol l-1 at room temperature and in tetrachloroethylene in the concentration 1.5 . 10-4 mol l-1 at temperatures above 65° C. True conformational changes are observable only with the least flexible amide IV which exists at room temperature in a C5 conformation. This conformational type is also highly populated in the valine derivative III, but is less important in the alanine and leucine derivatives I and II in which the intramolecularly bonded C7 and the distorted hydrogen-nonbonded conformations contribute seriously.

A solid‐state electrochemiluminescence sensor based on novel two‐dimensional Ti3C2 MXene

2021 ◽  
Author(s):  
Huanhuan Xing ◽  
Hongyin Xia ◽  
Yongchao Fan ◽  
Yuan Xue ◽  
Chao Peng ◽  
...  
Keyword(s):  
Solid State ◽  
Two Dimensional

Room Temperature Solvent-Free Synthesis of Monodisperse Magnetite Nanocrystals

2006 ◽  
Vol 6 (3) ◽  
pp. 852-856 ◽  
Author(s):  
X. R. Ye ◽  
C. Daraio ◽  
C. Wang ◽  
J. B. Talbot ◽  
S. Jin
Keyword(s):  
Oleic Acid ◽  
Solid State ◽  
Large Scale ◽  
Room Temperature ◽  
Solvent Free ◽  
Two Dimensional ◽  
New Process ◽  
High Boiling Point ◽  
Magnetite Nanocrystals ◽  
Solvent Free Synthesis

We have successfully demonstrated a facile, solvent-free synthesis of highly crystalline and monodisperse Fe3O4 nanocrystallites at ambient temperature avoiding any heating. Solid state reaction of inorganic Fe(II) and Fe(III) salts with NaOH was found to produce highly crystalline Fe3O4 nanoparticles. The reaction, if carried out in the presence of surfactant such as oleic acid–oleylamine adduct, generated monodisperse Fe3O4 nanocrystals extractable directly from the reaction mixture. The extracted nanoparticles were capable of forming self-assembled, two-dimensional and uniform periodic array. The new process utilizes inexpensive and nontoxic starting materials, and does not require a use of high boiling point and toxic solvents, thus is amenable to an environmentally desirable, large-scale synthesis of nanocrystals.

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