Recent Successes in Structural Studies of Thermotropic Liquid Crystalline Polymers

Lipatov, Yu.S.; Tsukruk, Vladimir V.; Шилов, В. В.

doi:10.1080/07366578408079447

Cited by 26 publications

(1 citation statement)

References 56 publications

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“…But ionic interactions are the same for tertiary amines (tetramethyl-1,3-propanediamine, tetraethyl-1,3-propanediamine, and pentamethyldiethylenetriamine), whereas only tetraethyl-1,3-propanediamine presents a significantly lower T nl temperature. A possible explanation arises from the comparison with liquid crystals with side-chain mesogenic units. , In the latter systems increasing the length of the flexible group which links the mesogenic unit to the main chain produces a decrease in the anisotropic–isotropic transition temperature because mobility is higher. Similarly, in the case of tetraethyl-1,3-propanediamine the length of the unit linked to nitrogen is larger than for the other samples (ethyl units face to methyl units).…”

Section: Discussionmentioning

confidence: 99%

Synthesis and Rheological Behavior of Supramolecular Ionic Networks Based on Citric Acid and Aliphatic Diamines

et al. 2012

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Novel supramolecular ionic networks were obtained by reacting citric acid and aliphatic diamines. A proton transfer reaction takes place between the carboxylic acid of citric acid and the amine group leading to the corresponding ionic carboxylate and quaternary ammonium groups. By this method, a series of supramolecular ionic networks were obtained due to the multiple ionic interactions between the corresponding citrate and diammonium molecules as observed by FTIR spectroscopy. Rheological analysis of the ionic networks was carried out considering frequency and temperature sweeps in small-amplitude oscillatory flow and viscous measurements in continuous flow. At low temperatures and/or high frequencies the ionic interactions brought about an elastic network or gel which vanished at high temperatures and/or low frequencies. The viscoelastic behavior was governed by a single relaxation time and a very high plateau modulus, G p = 5 × 106 Pa. The relaxation time showed an Arrhenius-like dependency with temperature, leading to draw diagrams of the physical states for each sample. The obtained supramolecular ionic networks based on different aliphatic diamine molecules did not show differences in their respective solid and liquid states. However, the frequency-dependent network–liquid transition temperature, T nl, varied with the chemical nature of the diamines. The higher T nl (45 °C) was found for the system that contains 1,3-diaminopropane which is attributed to stronger ionic bonds involving primary amines, with respect to ionic bonds with tertiary amines (between −1 and 32 °C). Comparing ionic networks obtained from different tertiary diamines, such as tetramethyl-1,3-propanediamine and tetraethyl-1,3-propanediamine, the lower T nl was observed in the latter, ascribed to a higher mobility of the aliphatic pendant groups.

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Section: Discussionmentioning

confidence: 99%

Synthesis and Rheological Behavior of Supramolecular Ionic Networks Based on Citric Acid and Aliphatic Diamines

et al. 2012

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Linear poly(etheraroylhydrazides): A correlation between number of methylene sequences and reticular structure

Gentile¹,

Laurienzo²,

Riva³

et al. 1997

J. Polym. Sci. B Polym. Phys.

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Thermal Characterization of Liquid Crystalline Materials

Ende¹,

Groeninckx²,

Reynaers³

1989

Bulletin des Soc Chimique

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SUMMARYDuring the last years there has been a significant interest in the field of liquid crystalline components, polymers in articuIar.[l.21' There is a definite need to use a wide range of methods to characterize these materials. fhermal properties need to ,be, examined properly in order to obtain the glass-transition temperature, melting, clearing and crystallization temperatures.The first part o this paper will give an introduction to the basic princi les of the liquid crystalline state. The outstanding properties as well as the required chemical structure wilfbe discussed. The second part deals with the characterization of these materials by means of optical, thermal and scattering techniques available in our laboratory.uid Crvstalline State Liquid crystals represent a state of molecular order that is intermediate between an isotropic liquid and a crystalline solid.13] These materials form anisotropic fluid phases that possess one-or two-dimensional positional and orientational order of the molecules. An anisotropic fluid can be obtained in two ways : either by dissolving small amounts of a LC component in a suitable solvent (lyotropic LC solution), or by heating a low or high molecular weight LC component above its melting point, (so called thermotropic LC). By heating up the thermotropic LC component to higher temperatures, it becomes isotropic. In the liquid crystalline state, the viscosity decreases drastically, which in the case of polymers is important with respect to the processability.Low and high molecular mass liquid crystals have found applications in a variety of technologies such as optical displays, electro-optical sensors, high strength fibers, processing aids and molecular composites. When polymers are processed in the liquid crystalline state, their anisotropy may be maintained in the solid state and might readily lead to the formation of materials with great strength in the direction of orientation.In general, the LC state can be subdivided as follows :

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Recent Successes in Structural Studies of Thermotropic Liquid Crystalline Polymers

Cited by 26 publications

References 56 publications

Synthesis and Rheological Behavior of Supramolecular Ionic Networks Based on Citric Acid and Aliphatic Diamines

Synthesis and Rheological Behavior of Supramolecular Ionic Networks Based on Citric Acid and Aliphatic Diamines

Linear poly(etheraroylhydrazides): A correlation between number of methylene sequences and reticular structure

Thermal Characterization of Liquid Crystalline Materials

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