scholarly journals Thermal and kinetic characteristics in non-isothermal conditions of some aromatic copolyethers containing an octomethylenic spacer

2003 ◽  
Vol 1 (4) ◽  
pp. 387-401
Author(s):  
Mihaela Prajinaru ◽  
Natalia Hurduc ◽  
Silvia Alazaroaie ◽  
Otilia Catanescu ◽  
Nicolae Hurduc
Keyword(s):  
Phase Transition ◽  
Thermal Stability ◽  
Liquid Crystalline ◽  
Degradation Mechanism ◽  
Stability Limit ◽  
Supplementary Information ◽  
Kinetic Characteristics ◽  
Characterization Methods ◽  
Good Thermal Stability ◽  
High Phase

AbstractThe paper presents a study of the thermal properties of some aromatic polyethers obtained by phase trasfer catalysis technique. The polymes were synthesized starting from 1,8-dichloro-octane and various bisphenols: 4,4′-dihydroxyazobenzene, 4,4′-dihydroxydiphenyl, bisphenol A and 2,7-dihydroxynaphthalene. Molecular simulations were performed in order to obtain supplementary information concerning the chain conformation and inter-chain interactions. The presence of azobenzenic moieties induces high phase transition values, situated near the thermal stability limit. Therefore, the thermogravimetrical study of these polymers is very important for establishing the temperature limits for DSC and optical microscopy studies. All the polymers present a good thermal stability situated above the isotropization values. In these circumstances no special precautions are necessary for the characterization methods of the liquid crystalline behavior. The kinetic characteristics suggest a similar degradation mechanism by successive reactions. The inter-chain interactions do not influence the thermostability of the samples if the polar surface of the polymer is situated below a certain value.

Synthesis and Properties of Biodegradable Liquid Crystalline Poly(ester-Urethane)s Based on Poly(L-Lactic Acid)

2013 ◽  
Vol 652-654 ◽  
pp. 459-462
Author(s):  
Ya Tong Guo ◽  
Zhu Zheng ◽  
Zhen Qi Hou ◽  
Jie Du
Keyword(s):  
Phase Transition ◽  
Thermal Stability ◽  
Lactic Acid ◽  
Physical Properties ◽  
Liquid Crystalline ◽  
Degradation Rate ◽  
Hydrolytic Degradation ◽  
Hexamethylene Diisocyanate ◽  
Solution Polymerization ◽  
Phase Transition Temperatures

A series of biodegradable segmented liquid crystalline poly(ester-urethane)s were prepared by solution polymerization of poly(L-lactic acid) (PLLA), mesogenic diol prepolymer poly(butylene terephthaloyldioxy dibenzoates) (MD), and hexamethylene diisocyanate (HDI). The MD content was varied from 0 to 40 mol% so that the effects of the mesogen content on the thermal and physical properties, and hydrolytic degradation were examined respectively. It was found that introducing mesogens units could increase the thermal stability and the elastic properties, while reduced the phase transition temperatures and the hydrolytic degradation rate.

Synthesis and Characterization of Novel Arylidene and Cardo Ester Bismaleimides and Poly(aminoaspartimide)s Therefrom

2003 ◽  
Vol 15 (3) ◽  
pp. 301-318 ◽  
Author(s):  
Vasile Cozan ◽  
Mitica Sava ◽  
Luminita Marin ◽  
Maria Bruma
Keyword(s):  
Thermal Stability ◽  
Liquid Crystalline ◽  
Polarized Light ◽  
Analysis Data ◽  
Synthesis And Characterization ◽  
Elemental Analysis Data ◽  
Scanning Calorimetry ◽  
Good Thermal Stability ◽  
H Nmr

Six new bismaleimides (BMIs) having arylidene or cardo cycloaliphatic internal moieties were prepared by reacting 4-maleimidobenzoyl chloride with various arylidene or cardo bisphenols. The structures of BMIs were confirmed using elemental analysis data and spectroscopic (IR, 1H-NMR) characterizations. Two poly(aminoaspartimide)s (PAAs) were synthesized to exemplify one of the post-reaction abilities of the BMIs. Thermotropic liquid crystalline behavior was observed by differential scanning calorimetry and polarized light microscopy. The thermal stability of BMIs and PAAs was determined by thermogravimetric analysis and they showed good thermal stability except BMI 10, containing a cyclopentanone unit, which decomposed around 235°C. In this paper, we discuss the synthesis and characterization of these materials.

Molecular design and synthesis of thermotropic liquid crystalline poly(amide imide)s with high thermal stability and solubility

e-Polymers ◽  
2017 ◽  
Vol 17 (2) ◽  
pp. 199-207 ◽  
Author(s):  
Yanbin Wang ◽  
Guangming Lu ◽  
Wenjie Wang ◽  
Meng Cao ◽  
Zhonglin Luo ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Liquid Crystalline ◽  
Molecular Design ◽  
Xrd Analysis ◽  
Proton Nuclear Magnetic Resonance ◽  
Scanning Calorimetry ◽  
Good Thermal Stability ◽  
Design And Synthesis ◽  
H Nmr ◽  
Melting Temperatures

AbstractA series of thermotropic liquid crystalline poly(amide imide)s (PAIs) with well-defined structure were prepared by the Yamazaki-Higashi phosphorylation method. To obtain the target polymers, several diimide diacid monomers (DIDAs) as mesogenic units were synthesized by the dehydration cyclization of aromatic anhydride with aliphatic 11-aminoundecanoic acid (AU). The chemical structure of these DIDAs and PAIs was confirmed via Fourier transform infrared (FTIR) and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Thermotropic liquid crystalline characteristics of the DIDAs and PAIs were investigated by differential scanning calorimetry (DSC), polarizing light microscopy (PLM) and X-ray diffraction (XRD) analysis. Encouragingly, all of these liquid crystalline PAIs exhibited good thermal stability, in which the decomposition temperatures are much higher than the melting temperatures of PAIs. Furthermore, the liquid crystalline PAIs can be dissolved into some common solvents such as dimethyl sulfoxide (DMSO) and m-cresol, which indicates these liquid crystalline PAIs could be processed not only by melting-processing but also by solution spin-coating.

scholarly journals Thermal behavior of some aromatic copolyethers containing a propylenic spacer

2005 ◽  
Vol 3 (1) ◽  
pp. 53-62 ◽  
Author(s):  
Nicolae Hurduc ◽  
Cristina Damian ◽  
Anca Tarus ◽  
Violeta Toader ◽  
Natalia Hurduc
Keyword(s):  
Thermal Stability ◽  
Thermal Degradation ◽  
Liquid Crystalline ◽  
Degradation Mechanism ◽  
Degradation Process ◽  
Stability Study ◽  
Maximum Temperature ◽  
Weakest Link ◽  
Starting Point ◽  
Thermal Degradation Process

AbstractThe main objective of this paper is to study the thermal stability of some aromatic copolyethers containing a propylenic spacer. Some of the investigated copolyethers displayed a liquid crystalline (LC) behavior, with the presence of the mesogenic groups in the main chain, inducing high values of the thermal transition temperatures. As a consequence, a thermal stability study was necessary to establish the maximum temperature value for the LC behavior characterization. A thermal degradation mechanism is proposed, taking into consideration the azobenzenic unit as the weakest link in the polymer chain and thus, the starting point of the thermal degradation process. The degradation mechanisms were correlated with the chemical structure and the polarity and conformation of the chains. Conformational analysis was performed using molecular simulations. Freeman-Caroll and Coats-Redfern methods were used to calculate some kinetic characteristics.

scholarly journals Liquid-crystalline fullerene-gold nanoparticles

RSC Advances ◽  
2015 ◽  
Vol 5 (35) ◽  
pp. 27224-27228 ◽  
Author(s):  
Thanh Tung Nguyen ◽  
Steeve Albert ◽  
Thi Le Anh Nguyen ◽  
Robert Deschenaux
Keyword(s):  
Thermal Stability ◽  
Gold Nanoparticles ◽  
Click Chemistry ◽  
Liquid Crystalline ◽  
Good Thermal Stability ◽  
Smectic A ◽  
Smectic A Phase

Liquid-crystalline [60]fullerene–gold nanoparticles were prepared by applying click chemistry. The materials display the smectic A phase and a good thermal stability.

scholarly journals Synthesis and photocatalytic properties of Sn–TiO2 nanomaterials

2020 ◽  
Vol 10 (01n02) ◽  
pp. 2060018
Author(s):  
E. M. Bayan ◽  
T. G. Lupeiko ◽  
L. E. Pustovaya ◽  
M. G. Volkova
Keyword(s):  
Phase Transition ◽  
Thermal Stability ◽  
Sol Gel ◽  
Rutile Phase ◽  
Photocatalytic Properties ◽  
Light Activation ◽  
X Ray ◽  
Tio2 Nanomaterials ◽  
Visible Light Activation ◽  
Thermal Stability Of

Sn-doped TiO2 nanomaterials were synthesized by sol–gel method. It was shown the phase compositions and phase transitions change with the introduction of different tin amounts (0.5–20[Formula: see text]mol.%). X-ray powder diffraction was used to study the effect of different tin amounts on the anatase–rutile phase transition. It was found that the introduction of ions increases the thermal stability of anatase modifications. The material’s photocatalytic activity was studied in reaction with a model pollutant (methylene blue) photodegradation under UV and visible light activation. The best photocatalytic properties were shown for material, which contains 5[Formula: see text]mol.% of Sn.

Thermal degradation kinetics of Opuntia Ficus Indica flour and talc-filled poly (lactic acid) hybrid biocomposites by TGA analysis

2021 ◽  
pp. 002199832110082
Author(s):  
Azzeddine Gharsallah ◽  
Abdelheq Layachi ◽  
Ali Louaer ◽  
Hamid Satha
Keyword(s):  
Thermal Stability ◽  
Lactic Acid ◽  
Thermal Degradation ◽  
Degradation Kinetics ◽  
Degradation Mechanism ◽  
Melt Processing ◽  
Thermal Degradation Kinetics ◽  
Poly Lactic Acid ◽  
Opuntia Ficus Indica ◽  
Model Free

This paper reports the effect of lignocellulosic flour and talc powder on the thermal degradation behavior of poly (lactic acid) (PLA) by thermogravimetric analysis (TGA). Lignocellulosic flour was obtained by grinding Opuntia Ficus Indica cladodes. PLA/talc/ Opuntia Ficus Indica flour (OFI-F) biocomposites were prepared by melt processing and characterized using Wide-angle X-ray scattering (WAXS) and Scanning Electron Microscope (SEM). The thermal degradation of neat PLA and its biocomposites can be identified quantitatively by solid-state kinetics models. Thermal degradation results on biocomposites compared to neat PLA show that talc particles at 10 wt % into the PLA matrix have a minor impact on the thermal stability of biocomposites. Loading OFI-F and Talc/OFI-F mixture into the PLA matrix results in a decrease in the maximum degradation temperature, which means that the biocomposites have lower thermal stability. The activation energies (Ea) calculated by the Flynn Wall Ozawa (FWO) and Kissinger Akahira Sunose (KAS) model-free approaches and by model-fitting (Kissinger method and Coats-Redfern method) are in good agreement with one another. In addition, in this work, the degradation mechanism of biocomposites is proposed using Coats-Redfern and Criado methods.

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