Structure formation in a poly-p-benzamide-sulphuric acid system

Papkov, S. P.; Iovleva, M. M.; Banduryan, S. I.; Ivanova, N. A.; Andreyeva, I.N.; Kalmykova, V.D.; Volokhina, A. V.

doi:10.1016/0032-3950(78)90164-8

Cited by 18 publications

(6 citation statements)

References 2 publications

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“…These analyses include electronic microscopy and polarization measurements reported by Papkov et al, who monitored the transitions and textures of an 11K PBA sample dissolved in 98% sulfuric acid. 19 For solutions with concentrations in the 8-13% w/w interval a nematic/isotropic phase coexistence was observed in the 20-60 °C region, ranges that are similar to the ones that we observe by NMR. Also in agreement with the NMR data, these analyses indicated an elevation in the T in clearing temperatures as polymer concentrations increase, leading eventually to the appearance of solid particles whose signal we would not be able to detect under the present spectroscopic conditions.…”

Section: Concentration and Temperaturesupporting

confidence: 84%

“…Before proceeding to the quantification of these data it is worth evaluating how the spectral changes that are detected by NMR compare with the picture available about PBA/H 2 SO 4 phase equilibria from other, non-NMR methods. These analyses include electronic microscopy and polarization measurements reported by Papkov et al ., who monitored the transitions and textures of an 11K PBA sample dissolved in 98% sulfuric acid . For solutions with concentrations in the 8−13% w/w interval a nematic/isotropic phase coexistence was observed in the 20−60 °C region, ranges that are similar to the ones that we observe by NMR.…”

Section: Resultssupporting

confidence: 66%

“…Numerous characterizations of the solid ⇄ nematic ⇄ isotropic equilibria that arise in PBA solutions have appeared in the literature. The majority of these measurements involved bulk calorimetric, solubility, optical, and rheometric analyses of the polymer dissolved in N,N -dimethylacetamide/LiCl, ,− while fewer studies focused on bulk optical, rheological, and susceptibility determinations of the polymer dissolved in absolute sulfuric acid. , We decided to focus the present investigation on the properties displayed by the latter solutions, as sulfuric acid is the solvent normally employed in the industrial processing of aramides .…”

Section: Introductionmentioning

confidence: 99%

“…The majority of these measurements involved bulk calorimetric, solubility, optical, and rheometric analyses of the polymer dissolved in N,N-dimethylacetamide/LiCl, 11,[14][15][16][17][18] while fewer studies focused on bulk optical, rheological, and susceptibility determinations of the polymer dissolved in absolute sulfuric acid. 19,20 We decided to focus the present investigation on the properties displayed by the latter solutions, as sulfuric acid is the solvent normally employed in the industrial processing of aramides. 13 Our experimental studies were based on nuclear magnetic resonance (NMR), a method whose capability to monitor molecular level properties of both solvent and solute in low molecular weight liquid crystals is well established.…”

Section: Introductionmentioning

confidence: 99%

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NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/Sulfuric Acid Solutions

Zhou

Frydman

1997

Macromolecules

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Natural abundance NMR methods were employed to analyze static and dynamic properties of poly(p-benzamide), the parent compound of the aramide family of polymers, dissolved in absolute sulfuric acid. Quantitative determinations of order in the liquid crystal phases arising in these systems were carried out with the aid of bidimensional 13 C NMR data collected in the solid phase and of total line shape simulations, and the parameters thus obtained were monitored as a function of temperature, concentration, and polymer molecular weight. These measurements revealed that by contrast to what had been inferred from previous macroscopic order determinations, the alignment of polymer molecules in their nematic domains is essentially independent of temperature. Existing measurements can still be explained in terms of a temperature-dependent isotropic a nematic equilibrium, whose presence and thermodynamics were unambiguously characterized by NMR. Dynamic aspects of this interphase equilibrium as well as of the intraphase molecular diffusion in the nematic region were explored by bidimensional and pulsed-gradient NMR methods. Spectroscopic results were analyzed in terms of thermal and athermal theories predicting the appearance of nematic phases in rigid anisometric polymers and compared with recent NMR observation on other lyotropic aramide solutions.

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Section: Concentration and Temperaturesupporting

confidence: 84%

Section: Resultssupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/Sulfuric Acid Solutions

Zhou

Frydman

1997

Macromolecules

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“…This process highlights the relevance of understanding the mechanisms by which controllable factors, such as concentration, temperature, molecular weight, and monomeric structures, affect the anisotropic ordering in these fluid systems. Substantial progress has already been made in this area, both in terms of experimentally monitoring order parameters in aramide solutions ,,− as well as in relating these order parameters to the statistical mechanics of the dissolved macromolecules. ,,,, …”

Section: Introductionmentioning

confidence: 99%

The Influence of Monomer Structures on the Liquid Crystalline Order of Aramide Polymers: An NMR Analysis

McElheny¹,

Frydman²,

Zhou³

et al. 1999

J. Phys. Chem. B

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Natural abundance NMR methods were employed to analyze the liquid crystalline behavior of poly(p-phenylene-2,6-naphthylamide) and poly(p-phenylene-4,4‘-biphenylamide), two members of the aramide polymer family. These macromolecules were dissolved in absolute sulfuric acid and the extent of order in their liquid crystal phases was evaluated with the aid of solid phase 13C tensor data and by total simulations of their lyotropic NMR line shapes as a function of temperature and concentration. These measurements revealed that as reported recently for other phenyl-based aramides, the nematic order of polymers in these lyotropic phases is essentially independent of temperature while slightly dependent on concentration. When considered in unison with these previous 13C NMR analyzes this study also suggests that nematic order in aramides can be controlled by the choice of the monomeric chemical structures, increasing along the series naphthyl ≲ phenyl < biphenyl. Although the origin of this trend is not apparent when polymers are considered in their preferred all-anti/all-trans backbone conformations, its nature can be rationalized in terms of macromolecular semiflexibility arguments involving syn↔anti rearrangements of consecutive amide groups. These rearrangements impart worm-like displacements to otherwise rigid macromolecules that help understand the observed trend in order parameters, while simultaneously explaining the relative disorder exhibited by these aramide solutions in comparison with rigid rod theoretical predictions.

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Lyotropic main chain liquid crystal polymers

Northolt

Sikkema

1990

Advances in Polymer Science

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Structure formation in a poly-p-benzamide-sulphuric acid system

Cited by 18 publications

References 2 publications

NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/Sulfuric Acid Solutions

NMR Analyses of Order and Dynamics in Poly(p-Benzamide)/Sulfuric Acid Solutions

The Influence of Monomer Structures on the Liquid Crystalline Order of Aramide Polymers: An NMR Analysis

Lyotropic main chain liquid crystal polymers

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