Rheology and Rheo-Optics of Polymer Liquid Crystals

Onogi, Shigeharu; Asada, Tadahiro

doi:10.1007/978-1-4684-3740-9_9

Cited by 203 publications

(105 citation statements)

References 40 publications

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“…), a strong thinning behavior appears where the domain structure is not evident at this stage [27]. These results are in agreement with the results of Kannan et al [29] and Dan et al [30] which suggested that the large amplitude oscillatory shear orientated the SCLCPs.…”

Section: Rheological Propertiessupporting

confidence: 91%

“…Figure 8 represents the viscosity properties of the polymers over the temperature range of phase transitions. Both polymers exhibit Bingham body-like flow behavior at 100°C and 110°C which shows "three region flow curves" as characterized by Onogi and Asada [27,28]. At low values of shear rate ( g Á <1 s ), where the domains appear to decrease in size with increasing shear rate.…”

Section: Rheological Propertiesmentioning

confidence: 93%

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Naphthalene group containing side chain liquid crystalline polymers and their rheological behavior

et al. 2013

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A new polymerizable macromer containing naphthalene ring in the mesogen, 4-butoxyphenyl 6-(6-(methacryloyloxy)hexyl)-2-naphthoate, has been synthesized. The chemical structure of the macromer was confirmed by FTIR, 1 H NMR, 13 C NMR and liquid crystal behavior was confirmed by polarized optical microscope (POM) and small angle X-ray (SAXS). Results from the POM showed nematic phase appearing at 101.9°C and smectic phase at 83.8°C while differential scanning calorimetry (DSC) suggested presence of a wide mesophase range between 50 and 104°C. This macromer was used to synthesize a series of side-chain liquid crystal polymers (SCLCPs) with different molecular weights having narrow polydispersity (PDI) values via living atom transfer radical polymerization (ATRP). The mesomorphic properties of the liquid crystal macromer and polymers were characterized by POM, DSC and SAXS. In addition, the frequency behavior of the polymers in a smectic phase is characterized by the storage modulus, G', leveling off, at low frequencies. Complex viscosities, |η*| of the smectic phase exhibited a shear thinning behavior over the shear rates investigated.

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Section: Rheological Propertiessupporting

confidence: 91%

Section: Rheological Propertiesmentioning

confidence: 93%

Naphthalene group containing side chain liquid crystalline polymers and their rheological behavior

et al. 2013

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“…Such steady-state region is known as region I and is another characteristic property of the liquid crystalline polymers observed in a variety of systems. [41][42][43] This is thought to be a universal behavior caused by a defect ridden structure that is often denoted as "texture" or "domain structure". 43 The reason we more clearly observed the flow region I at a temperature higher than the ambient is not clear.…”

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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“…For end-tethered CPNCs, at low or moderate clay concentrations, the shear flow may be interpreted using LCP theories. Following the Onogi and Asada [1980] classification, three regions of flow might be identified:…”

Section: Discussionmentioning

confidence: 99%

“…This phase morphology is characterized by local orientation, evident in rheooptical studies. As shown in Figure 16.3, there are three regions of flow for the nematic LCP [Onogi and Asada, 1980;Wissbrun, 1981]: (I) a shear-thinning region at low deformation rates, (II) a plateau region, and (III) a power-law shear thinning region. The structure in region I is highly variable, dependent on the specimen history and resulting polydomain morphology.…”

Section: Model Suspension For Pncsmentioning

confidence: 99%