Phase transfer catalysis in polycondensation processes XXIV. On the thermal stability of some aromatic polyethers containing a propylenic spacer

Tarus, Anca; Hurduc, Nicolae; Catanescu, Otilia; Cobzaru, Cecilia

doi:10.1016/s0141-3910(99)00169-x

Cited by 9 publications

(5 citation statements)

References 15 publications

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“…In our previous studies, the molecular modeling was very helpful in explaining the speci¯c degradation phenomena [8,12,13] or supra-molecular behavior [14,15,16,17]. If the polar surface is less than 5-5.5%, these studies indicate that the degradation process is not a®ected by the chain polarity [12,13]. This fact was con¯rmed by the present investigations for all the polymers whose polar surfaces were situated below 3.2%.…”

Section: Resultssupporting

confidence: 61%

“…For a better understanding of this behavior, theoretical conformational analyses were e®ectuated. In our previous studies, the molecular modeling was very helpful in explaining the speci¯c degradation phenomena [8,12,13] or supra-molecular behavior [14,15,16,17]. If the polar surface is less than 5-5.5%, these studies indicate that the degradation process is not a®ected by the chain polarity [12,13].…”

Section: Resultsmentioning

confidence: 97%

“…The analysis performed on the synthesized polymers evidenced a relatively low thermal stability of the polyethers containing azo groups compared with those without azo moieties. In these cases the temperature limit corresponding to the starting of the weight loss was situated around 250 ± C, below the isotropization temperature [13,19]. Therefore, a standard characterization of the liquid crystalline behavior (two heating/cooling scans) was impossible.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2003

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The paper presents a study of the thermal properties of some aromatic polyethers obtained by phase transfer catalysis technique. The polymers 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 in®uence the thermostability of the samples if the polar surface of the polymer is situated below a certain value.

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Section: Resultssupporting

confidence: 61%

Section: Resultsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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

et al. 2003

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“…This influence of the chain polarity on the thermal behaviour is also supported by similar studies previously performed on the copolyethers containing a propylenic spacer. It was established that if the structural unit of the copolymer contains only one "polar" bisphenol (such as DHAB), and the other co monomer is either biphenyl or bisphenol A, the starting degradation temperature depends on the copolymer composition [12].…”

Section: Resultsmentioning

confidence: 99%

Thermal behavior of some aromatic copolyethers containing a propylenic spacer

et al. 2005

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Abstract:The 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.

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“…For liquid crystalline (LC) polymers with mesogenic groups in the main chain, it is very important to know the limits of the thermal stability, taking into consideration the high values of the temperature transitions. Due to the fact that there are not many reported studies [6][7][8][9][10][11] concerning the thermal stability of the aromatic polyethers, we decided to extend the thermal investigation to polyethers without LC properties.…”

Section: Introductionmentioning

confidence: 99%

The Non-isothermal Degradation Process of some Polyethers and Azo-polyethers

Hurduc

Lisă

Damian

et al. 2007

High Performance Polymers

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The paper presents a non-isothermal kinetic study of the degradation process of some aromatic copolyethers containing a tetra-methylenic spacer. The polymers were synthesized using the phase transfer catalysis technique, starting from 1,4-dichlorobutane and various bisphenols (4,4'-dihidroxyazobenzene, 4,4'-dihydroxydiphenyl, bisphenol A and 2,7-dihydroxynaphthlene). Dynamic thermal analysis methods such as ATG, DTG and ATD were used. In order to work out the basic kinetic parameters and the reliance between activation energy and conversion degree, differential methods based on the `order reaction model' were applied and standard kinetic models were also used. The thermostability of the good samples up to 320°C was demonstrated. The degradation mechanism took place by successive reactions, controlled by a nucleation process influenced by the polymer molecular structure.

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Phase transfer catalysis in polycondensation processes XXIV. On the thermal stability of some aromatic polyethers containing a propylenic spacer

Cited by 9 publications

References 15 publications

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

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

Thermal behavior of some aromatic copolyethers containing a propylenic spacer

The Non-isothermal Degradation Process of some Polyethers and Azo-polyethers

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