New information concerning spontaneous elongation of acetate fibers

Shipovskaya, A. B.; Timofeeva, G. N.

doi:10.1134/s0965545x07110089

Cited by 8 publications

(6 citation statements)

References 6 publications

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“…The solvent purity was checked spectroscopically. According to published data [6,7], DMSO and NM favor formation of the LC state in cellulose esters, whereas TCE does not exhibit such property. At high concentrations of the crystallizing rigid-chain CTA, in accordance with the polymer-solvent phase diagrams [6,8], the LC and crystalline phases can coexist.…”

Section: Methodsmentioning

confidence: 87%

“…According to the phase diagrams of the CTA-NM system [6], at this composition the crystalline and LC phases of the polymer can coexist. For the CTA-DMSO system [7], this composition corresponds to the two-phase region in which the isotropic and LC phases coexist. The photomicrographs of the CTA fi lm before and after sorption of NM and DMSO vapors, taken in the polarized light (Fig.…”

Section: Mnmentioning

confidence: 99%

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Modification of the structure of cellulose triacetate films in the course of solvent vapor sorption

2014

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The production of fi lms used as materials for package, fi lters, water treatment membranes, electrical insulation, photography, and motion pictures is a promising application fi eld of cellulose acetates (CAs) prepared from a renewable raw material. Because of large-scale practical use and availability, cellulose derivatives still attract much researchers' attention, since many problems associated with their complicated structural organization remain to be solved. The physicomechanical and ecological properties of materials based on cellulose esters are largely determined by the initial structure of the polymeric material, by its changes under the infl uence of solvents, and by the nature of solvents used for manufacturing the material. Studies of the behavior of CAs in various solvents are also of particular interest today, because cellulose esters characterized by increased chain rigidity tend to ordering and formation of liquid crystal (LC) state in solutions and melts, and also in the presence of organic solvent vapors [1,2]. Hydrogen bonds and donor-acceptor interactions play a signifi cant role in the formation of the anisotropic state of polymer systems and in structural transformations on the molecular and supramolecular levels [3,4]. One of the most sensitive methods for analysis of the structure of macromolecules and intermolecular interactions caused by hydrogen bonds is Fourier IR spectroscopy.This method was used previously [4] for studying the LC formation in cellulose diacetate fi lms in nitromethane and dimethylsulfoxide vapors.This work was aimed at studying intra-and intermolecular interactions in cellulose triacetate fi lms in the course of sorption of vapors of solvents differing in the chemical nature and at evaluating the structure of the polymeric fi lm material. EXPERIMENTALExperiments were performed with cellulose triacetate (CTA) fi lms prepared from a 1.5% solution of CTA in methylene chloride. Films were prepared from cellulose acetate produced in Russia by heterogeneous acetylation and saponifi cation, viscosity-average molecular mass М η = 7.3 × 10 4 . The content of acetate groups, according to the certifi cate data, was 60.5%. Films were prepared in Petri dishes. The solvent was evaporated at room temperature in an air thermostat for 24 h and then in a vacuum box to constant weight without heating. The fi lm thickness was 50-80 μm.As solvents we used dimethylsulfoxide (DMSO, aprotic strongly donor polar solvent, donor number DN SbCl 5 = 28.9, dipole moment μ = 3.96 D [5]), nitromethane (NM, Abstract-Intermolecular interaction and structure of cellulose triacetate fi lms in the course of sorption of dimethylsulfoxide, nitromethane, and tetrachloroethane vapors were studied by Fourier IR spectroscopy, X-ray diffraction analysis, and polarization microscopy. Quantitative ratio of different types of intra-and intermolecular hydrogen bonds in polymer fi lms was estimated. Changes in the structure of cellulose triacetate fi lms in the course of solvent vapor sorption were discussed from...

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Section: Methodsmentioning

confidence: 87%

Section: Mnmentioning

confidence: 99%

Modification of the structure of cellulose triacetate films in the course of solvent vapor sorption

2014

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“…Spontaneous transition to an LC state is possible for them under certain thermodynamic conditions, which has been confirmed in the literature [23][24][25]. The possibility of transition of the CTA-nitromethane system to an LC phase is also supported by [13,26]; the effect of spontaneous elongation of CTA-based fibers and films in nitromethane vapor [3,[27][28][29] speaks for this as well. We note that the selective solvation of the residual OH groups in CTA with nitromethane predetermines the realization of rather rigid, extended helical conformations of macromolecules [27,29].…”

Section: Resultsmentioning

confidence: 60%

Phase Analysis of the Cellulose Triacetate-Nitromethane System

Shipovskaya

Gegel

Shmakov

et al. 2012

International Journal of Polymer Science

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A comprehensive study was made on the cellulose triacetate-nitromethane system to explore its phase separation within ranges 2–25 wt.% and−5÷+80°Cby means of polarization light and electron microscopy, the turbidity spectrum method, differential thermal and X-ray analyses, and rheological techniques. The physical state of the polymer was identified within the phase coexistence boundaries on the phase diagram which included three types of phase separation (amorphous (with a UCST atTcr=57∘Candccr=7.3 wt.%), crystal, and liquid crystal). The boundaries of the regions determining the coexistence of the liquid crystal (LC) and the partly crystal phase were found to be inside the region of amorphous liquid-liquid phase separation. For cellulose ester-solvent systems, this state diagram is the first experimental evidence for the possibility of coexistence of several phases with amorphous, LC, and crystal polymer ordering.

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“…A similar property was subsequently established to be characteristic of systems with not only NM but also other mesophasogenic (forming an LC phase with cellulose acetates) solvents, trifluoroacetic acid (TFAA), and dimethyl sulfoxide (DMSO), with some specific features in each case 10, 11, 14. These unusual phenomena were found to be due to structural reorganizations of the polymeric matrix, probably orientation, elongation, and ordering of chains, conformation transitions of macromolecules (anisometric coil‐helix ones), and so on 12, 13.…”

Section: Introductionmentioning

confidence: 92%

“…Absorption of the vapors of solvents known as “mesophasogenic” solvents (which form a lyotropic LC phase with a given polymer) by a solid polymer sample can be a method of preparing highly oriented anisotropic structures 9–14. In comparison with polymer swelling and dissolution directly in a liquid medium, the solvent's vapor sorption proceeds much more slowly.…”

Section: Introductionmentioning

confidence: 99%

Optical activity of the anisotropic phases of cellulose acetates

Shipovskaya

Shmakov

Kazmicheva

et al. 2009

J Polym Sci B Polym Phys

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In this study, the optical activity of cellulose di and triacetate films with a highly oriented vitrified structure was studied. The systems possess high values of specific optical rotation [a], which is in favor of the formation of a cholesteric mesophase.[a] depends on the sample orientation angle relative to the light polarization vector in the plane perpendicular to the light ray (optical activity anisotropy). This dependence (indicatrix) is irregular and is described by a distorted sinusoid in the Cartesian coordinates. The results of indicatrix decomposition into harmonic components are discussed, with the contributions of the isotropic and anisotropic components (each with the corresponding structural element of a certain symmetry type) being separated.

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New information concerning spontaneous elongation of acetate fibers

Cited by 8 publications

References 6 publications

Modification of the structure of cellulose triacetate films in the course of solvent vapor sorption

Modification of the structure of cellulose triacetate films in the course of solvent vapor sorption

Phase Analysis of the Cellulose Triacetate-Nitromethane System

Optical activity of the anisotropic phases of cellulose acetates

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