Commentary: Reflections on “Rheology of concentrated solutions of poly(γ-benzyl-glutamate),” by Gabor Kiss and Roger S. Porter,J. Polym. Sci., Polym. Symp., 65, 193 (1978)

Kiss, Gábor Dávid

doi:10.1002/polb.1996.936

Cited by 33 publications

(51 citation statements)

References 17 publications

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“…Our finding clearly indicated that S R depended on the phase of the solution as the shear viscosity did. This trend of S R behavior was similar to the first normal stress difference behavior 20,21 and the die swell behavior. [1][2][3][4] Consequently, the elastic properties for the liquid crystal-forming system depended on the phase of the system as the viscometric properties did.…”

Section: Dependence Of S R On Shear Stress Prior To Recoverysupporting

confidence: 69%

Recoverable shear strain of liquid crystal‐forming concentrated hydroxypropyl cellulose solutions

Suto

Mitamura

Sasaki

2002

J of Applied Polymer Sci

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ABSTRACT:The recoverable shear strain (S R ) for the liquid crystal-forming hydroxypropyl cellulose solutions was determined by means of a concentric cylinder rotational apparatus as functions of shear stress prior to recovery and concentration of the solutions at 30°C. S R greatly depended on shear stress and concentration; the phase of the solution (the single phase or biphase) governed the dependences of S R on stress and concentration. S R increased with increasing stress for the single phase and decreased for the biphase. S R seemed to be related to the die swell (B): S R ϰ B n . S R exhibited a maximum and a minimum with respect to concentration. S R for the cellulosic cholesteric liquid crystalline solutions was greater than that for the isotropic solutions. A model was proposed for explaining the greater S R .

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Section: Dependence Of S R On Shear Stress Prior To Recoverysupporting

confidence: 69%

Recoverable shear strain of liquid crystal‐forming concentrated hydroxypropyl cellulose solutions

Suto

Mitamura

Sasaki

2002

J of Applied Polymer Sci

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“…The response of reaching a viscosity maximum, which then falls sharply is a typical response of lyotropic mesophases. 18,30,35,[37][38][39] As the concentration of rods in the isotropic phase increases, rotation is hindered sterically and the viscosity increases. At some critical concentration, the polysaccharide rods align to lower their free energy, where each rod now has less rotational hindrance and the increased alignment lowers the viscosity.…”

Section: Resultsmentioning

confidence: 99%

Isotropic−Nematic Phase Equilibrium and Phase Separation of κ-Carrageenan in Aqueous Salt Solution: Experimental and Theoretical Approaches

Chronakis

Ramzi

2002

Biomacromolecules

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The behavior of chiral-nematic and isotropic phases of helical κ-carrageenan in aqueous solution of sodium iodide was compared with that of the anisotropic biphasic phase that contains both these phases. On the basis of birefringence, rheology, chemical analysis, average molecular weight, and polydispersity index measurements, we derived a number of characteristic differences as well as similarities between these phases, over a range of polysaccharide concentrations obtained by the dilution of each phase. For example, we assessed the critical concentration of an isotropic-anisotropic transition (C i ), the temperature of the anisotropic-isotropic phase shift during thermal heating-cooling cycles, and the viscosity changes due to the phase shift and due to the diminishing of the helical conformation. We also demonstrated how the different phases and their dilutions behave under the effect of shear and frequency of oscillation and how the viscoelastic properties vary in each phase and discussed the isotropic and anisotropic liquid crystal controlling behavior mechanisms. From a theoretical point of view, we propose to combine the wormlike chain model for semiflexible polyelectrolytes interacting via both hard-core and electrostatic repulsion to assess the concentration of isotropic-nematic transition, to assess the coexistence concentration range, and to determine the effects of charge by applying the effective diameter and a twisting effect. IntroductionThe carrageenans are linear, sulfated polygalactans extracted from various species of marine red algae, (i.e., Eucheuma cottoni, Eucheuma spinosum, Gigartina acicularis). 1,2 The primary structure is based on a repeating disaccharide sequence of 1,3-linked -D-galactopyranose and 1,4-linked 3,6-anhydro-D-galactopyranose residues. κ-and ι-carrageenan are the two best known gelling varieties.Rigid and semirigid macromolecules can form gels, but there is also a possibility to form ordered phases (nematic, chiral nematic, smectic, hexatic) or both gels and liquid crystalline phases. 3 The liquid crystalline phase is caused by restrictions on rotation, which in turn are caused by volume exclusion for the polymers of high axial ratios. Most experimental investigations on κ-carrageenan (KC) have dealt with conditions where gel formation or aggregations of the helices occur, therefore preventing the development of longrange liquid crystalline order. However, binding of iodide to the (negatively charged) KC helix increases the charge density, thus preventing aggregation and further gelation of the helices. 4,5 In fact, this was demonstrated for sodium iodide concentration of 0.1 M for polymer concentrations up to about 1 g/L. For higher values of sodium iodide concentration, aggregation does indeed take place, nevertheless, at a reduced extent. 6 The binding of iodide explains why the KC solutions require sodium iodide as a solvent to give a nematic liquid crystalline phase. 4 These solutions show a macroscopic phase separation into one anisotropic bottom phase and one isot...

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“…Fig. 4.109 shows an example of the viscosity variation throughout the whole concentration range, from isotropic to anisotropic state, for a poly-y-benzylglutamate solution [549]. The viscosity curve goes through a maximum, which is more pronounced and sharp at low shear rates.…”

Section: Liquid Crystalsmentioning

confidence: 98%

Rheology of polysaccharide systems

Lapasin

Pricl

1995

Rheology of Industrial Polysaccharides: Theory and Applications

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The transport properties and, specifically, the rheological behavior of real and complex materials such as polysaccharide systems can be significantly affected by several factors, mainly related to molecular and supermolecular features. Most of these factors are common to all polymeric systems, as they have universal character; others are peculiar to carbohydrate polymers. If we bear in mind the concepts discussed in §1.4, we can easily imagine for polysaccharides a variety of structural conditions much wider than that generally observed for synthetic polymers. On both molecular and supermolecular scales, polysaccharides possess special characteristics that reflect specific behavior so that different classes of materials can be identified.Let us consider the molecular scale first: at this level, the polymer backbone and its related features, such as its length in solution, shape, stitfuess and the eventual presence of ionizable groups, playa major role in determining the macroscopic properties of the system, including its rheology. Many of these molecular parameters correlate among themselves (e.g. chain stitfuess and length); others must be combined with external factors such as, for instance, the characteristics of the solvent medium. These latter may, in turn, exert an influence on the conformation adopted by the macromolecule in the medium itself, as well as on the possibility of forming supermolecular structures. In other words, changes in ionic strength, the nature of counterions, temperature or other solvent parameters may induce a conformational transition, thus modifying the hydrodynamic resistance of the macromolecule to flow. Also, if the polymer concentration is high enough, the variations described above may promote structural changes at a supermolecular level and, accordingly, modifications in the rheological behavior. Before leaving this brief comment on solvent characteristics we must mention the viscosity although, R. Lapasin et al. (eds.), Rheology of Industrial Polysaccharides: Theory and Applications

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Commentary: Reflections on “Rheology of concentrated solutions of poly(γ-benzyl-glutamate),” by Gabor Kiss and Roger S. Porter,J. Polym. Sci., Polym. Symp., 65, 193 (1978)

Cited by 33 publications

References 17 publications

Recoverable shear strain of liquid crystal‐forming concentrated hydroxypropyl cellulose solutions

Recoverable shear strain of liquid crystal‐forming concentrated hydroxypropyl cellulose solutions

Isotropic−Nematic Phase Equilibrium and Phase Separation of κ-Carrageenan in Aqueous Salt Solution: Experimental and Theoretical Approaches

Rheology of polysaccharide systems

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