scholarly journals Thermotropic Liquid-Crystalline Properties of Viologens Containing 4-n-alkylbenzenesulfonates

Crystals ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 77 ◽  
Author(s):  
Pradip Bhowmik ◽  
Anthony Chang ◽  
Jongin Kim ◽  
Erenz Dizon ◽  
Ronald Principe ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Differential Scanning Calorimetry ◽  
Fourier Transform ◽  
Liquid Crystalline ◽  
Metathesis Reaction ◽  
Scanning Calorimetry ◽  
Chemical Structures ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Melting Transitions

A series of viologens containing 4-n-alkylbenzenesulfonates were synthesized by the metathesis reaction of 4-n-alkylbenzenesulfonic acids or sodium 4-n-alkylbezenesulfonates with the respective viologen dibromide in alcohols. Their chemical structures were characterized by Fourier Transform Infrared, 1H and 13C Nuclear Magnetic Resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry and polarizing optical microscopy. They formed LC phases above their melting transitions and showed isotropic transitions. As expected, all the viologen salts had excellent stabilities in the temperature range of 278–295 °C as determined by thermogravimetric analysis.

scholarly journals Thermotropic Liquid-Crystalline and Light-Emitting Properties of Bis(4-aalkoxyphenyl) Viologen Bis(triflimide) Salts

Molecules ◽  
2020 ◽  
Vol 25 (10) ◽  
pp. 2435
Author(s):  
Pradip K. Bhowmik ◽  
Muhammed Kareem M. Al-Karawi ◽  
Shane T. Killarney ◽  
Erenz J. Dizon ◽  
Anthony Chang ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Variable Temperature ◽  
X Ray Diffraction ◽  
Metathesis Reaction ◽  
Scanning Calorimetry ◽  
Thermal Stabilities ◽  
Light Emitting ◽  
Chemical Structures ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance

A series of bis(4-alkoxyphenyl) viologen bis(triflimide) salts with alkoxy chains of different lengths were synthesized by the metathesis reaction of respective bis(4-alkoxyphenyl) viologen dichloride salts, which were in turn prepared from the reaction of Zincke salt with the corresponding 4-n-alkoxyanilines, with lithium triflimide in methanol. Their chemical structures were characterized by 1H and 13C nuclear magnetic resonance spectra and elemental analysis. Their thermotropic liquid-crystalline (LC) properties were examined by differential scanning calorimetry, polarizing optical microscopy, and variable temperature X-ray diffraction. Salts with short length alkoxy chains had crystal-to-liquid transitions. Salts of intermediate length alkoxy chains showed both crystal-to-smectic A (SmA) transitions, Tms, and SmA-to-isotropic transitions, Tis. Those with longer length of alkoxy chains had relatively low Tms at which they formed the SmA phases that persisted up to the decomposition at high temperatures. As expected, all of them had excellent thermal stabilities in the temperature range of 330–370 °C. Their light-emitting properties in methanol were also included.

scholarly journals SYNTHESIS OF BENZOXAZINE MONOMER WITH LOW CURING TEMPERATURE FROM RENEWABLE DIPHENOLIC ACID, BENZYLAMINE AND PARAFORMALDEHYDE

2018 ◽  
Vol 55 (1B) ◽  
pp. 63
Author(s):  
Cao Xuan Viet
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Differential Scanning Calorimetry ◽  
Fourier Transform ◽  
Exothermic Peak ◽  
Curing Temperature ◽  
Carboxyl Groups ◽  
Polymerization Temperature ◽  
Scanning Calorimetry ◽  
Monomer Structure ◽  
13C Nuclear Magnetic Resonance

The aim of this study was to examine the use of renewable diphenolic acid (DPA) as starting materials together with benzylamine and paraformaldehyde for the synthesis of novel polybenzoxazine resin with low curing temperature. The monomer structure was confirmed by 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. Differential scanning calorimetry (DSC) was also used to study crosslinking behavior of synthesized material. The benzoxazine monomer exhibited low exothermic peak with the onset around 162 °C, which is significantly lower than conventional benzoxazines derived from bisphenol A. The presence of carboxyl groups in monomer structure is responsible for the low polymerization temperature of this monomer.

scholarly journals Novel banana-discotic hybrid architectures

2009 ◽  
Vol 5 ◽  
Author(s):  
Hari Krishna Bisoyi ◽  
H T Srinivasa ◽  
Sandeep Kumar
Keyword(s):  
Differential Scanning Calorimetry ◽  
Optical Microscopy ◽  
Elemental Analysis ◽  
Liquid Crystalline ◽  
Scanning Calorimetry ◽  
Spectral Techniques ◽  
Design And Synthesis ◽  
Chemical Structures ◽  
Crystalline Property ◽  
Liquid Crystalline Property

Here we present the design and synthesis of novel banana-discotic dimers and banana-bridged discotic dimers. The chemical structures have been characterized by spectral techniques and elemental analysis. The thermal behaviors of the compounds have been investigated by polarizing optical microscopy and differential scanning calorimetry. None of these synthesized compounds exhibit any liquid crystalline property probably because of the incompatibility of the bent-core with the discotic core.

Effect of Two Diferrent Mesogens on Liquid-Crystalline Properties of Chiral Side-Chain Liquid-Crystalline Polysiloxanes

2011 ◽  
Vol 415-417 ◽  
pp. 1395-1398
Author(s):  
Ji Wei Wang ◽  
Jun Qing Zi ◽  
Li Xian He ◽  
Guang Yong Chen ◽  
Yan Zhong Yang
Keyword(s):  
Liquid Crystalline ◽  
Proton Nuclear Magnetic Resonance ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Cholesteric Phase ◽  
Long Wavelength ◽  
Crystalline Polymers ◽  
Chemical Structures ◽  
Nuclear Magnetic Resonance Spectra ◽  
Temperature Ranges

Abstract. A series of liquid crystalline polysiloxanes were synthesized by cholesteric LC monomer and nematic LC monomer. The chemical structures and liquid-crystalline properties of the monomers and polymers were characterized by various experimental techniques including Fourier transform infrared (FTIR), proton nuclear magnetic resonance spectra (1H-NMR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA) , X-ray diffraction measurements (XRD) and polarizing optical microscopy (POM). All the liquid crystalline polymers showed liquid crystalline properties with wide mesophase temperature ranges. For the polymers bearing only of one nematic LC monomer, it showed nematic phase, while others showed cholesteric phase. With increase the content of nematic LC monomer in the polymers from P1 to P7, the glass transition temperature and the isotropic temperature increased on heating circles. Reflection spectra of cholesteric mesophase of the series of polymers showed that the reflected wavelength shifted to long wavelength with increase content of nematic LC monomer in the polymers in the polymer systems, suggesting that helical pitch (P) become long.

Thermotropic mesomorphism in aqueous dispersions of 1-palmitoyl-2-oleoyl- and 1,2-dilauroyl-phosphatidylglycerols in the presence of excess Na+ or Ca2+

1983 ◽  
Vol 61 (8) ◽  
pp. 882-891 ◽  
Author(s):  
Blair D. Fleming ◽  
Kevin M. W. Keough
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Differential Scanning Calorimetry ◽  
Phospholipase D ◽  
Liquid Crystalline ◽  
Resonance Spectroscopy ◽  
Scanning Calorimetry ◽  
Aqueous Dispersions ◽  
Observed Behaviour ◽  
Enthalpy Of Transition ◽  
Stable Forms

1-Palmitoyl-2-oleoyl-sn-glycero-3-phospho-rac-glycerol (POPG) and 1,2-dilauroyl-sn-glycero-3-phospho-rac-glycerol (DLPG) have been made by the conversion of the appropriate lecithins in the presence of crude phospholipase D and excess glycerol. Aqueous dispersions of the lipids have been examined by differential scanning calorimetry and 31P-nuclear magnetic resonance spectroscopy. When dispersed in excess Na+ at pH 7, POPG and DLPG underwent gel to liquid-crystalline phase transitions at −2.0 ± 1.3 and −3.7 ± 1.9 °C, respectively. The enthalpy of transition for POPG in excess Na+ was 6.2 ± 0.3 kcal∙mol−1 (1 cal = 4.1868 J), but the value for DLPG in Na+ was variable. In the presence of excess Ca2+ at pH 7, both phospholipids displayed complex thermotropic mesomorphism. For DLPG in the presence of excess Ca2+, thermal events did not occur at the same temperatures as did those for POPG in excess Ca2+. The complexity of the observed behaviour may have arisen because of the formation of intermediate forms which slowly interconverted to more stable forms.

scholarly journals Extraction of Lignin from Empty Fruit Bunch Fiber via Microwave-Assisted Acid Hydrotrope Solvent

2021 ◽  
Vol 1 (2) ◽  
pp. 26-33
Author(s):  
Rasidi Roslan ◽  
Muhammad Nor Arifin Yaakob ◽  
Ms Fathihah
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Differential Scanning Calorimetry ◽  
Fourier Transform ◽  
Infrared Spectroscopy ◽  
Reaction Time ◽  
Thermogravimetric Analysis ◽  
Empty Fruit Bunch ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Microwave Assisted

Lignin is a sub-product from lignocellulose apart from cellulose and hemicellulose that produced from empty fruit bunch fiber (EFB). Lignin has low solubility and reactivity due to its bulky macromolecule structre. Being one of the wastes that being generated in massive amount, many alternatives has been taken to transform lignin into valuable products. To do so, many reactions are needed for the lignin to go through. In this study, lignin will be extracted from empty fruit bunch (EFB) with the aid of acid hydrotrope concentration of 30 % and microwave assisted with various extraction heating time and temperature. Characterization of lignin is done using Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetric analysis (TGA), Differential Scanning Calorimetry (DSC) and Nuclear magnetic resonance (NMR) while Scanning Electron Microscopy (SEM) and X-ray Powder Diffraction (XRD) used to characterize residues. The highest percentage of lignin yield and its purity obtained are 19.47 % and 96.63 % with the reaction time and temperature of the microwave is 30 minutes and 90 °C. From Fourier Transform Infrared Spectroscopy (FTIR), a wide band at 3430.09 cm-1 and 3413.45 cm-1 are observed due to O-H stretching vibration. As for peak at 1123.17 cm-1 and 1051.26 cm-1, it correspond to syringyl and guaicyl unit in both lignin and raw EFB. As for Thermogravimetric analysis (TGA), it shows that lignin decomposes slowly compared to raw EFB due to the aromatic structure of lignin that is very stable, therefore leading to difficulty of decomposing while from Differential Scanning Calorimetry (DSC), after removing cellulose and hemicellulose, glass transition temperature (Tg) obtained from lignin DSC spectroscopy is 193.05 °C at heat flow of 1.15 mW/mg. Next, from Nuclear magnetic resonance (NMR) spectroscopy, the signals observed around 6.5 – 8.0 ppm indicate aromatic H in syringyl and guaiacyl unit only at lignin spectra while at 3.3 – 4.0 ppm, raw EFB has an intense peak compared to lignin which attribute to methoxyl group. When the residue of the lignin as well as the raw EFB powder is characterized using X-ray Powder Diffraction (XRD), the crystallinity index of the lignin with reaction time and temperature of the microwave 30 minutes and 90 °C is the highest, 69.28 %. As a conclusion, an admissible percent of lignin yield and purity is able to be obtained with addition of acid hydrotrope depending on the variables. From the spectroscopies characterization, it is proved that lignin characteristics and properties are compatible for the production of new and value added products.

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