Atomic Force Microscopy Study of Hydroxypropylcellulose Films Prepared from Liquid Crystalline Aqueous Solutions

Godinho, M. H.; Fonseca, José Simões da; Ribeiro, A. C.; Melo, L.V.; Brogueira, P.

doi:10.1021/ma0118769

Cited by 46 publications

(44 citation statements)

References 16 publications

(21 reference statements)

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“…It is undoubtedly birefringent, and orientationally aligned, as expected for a drawn polymer fiber. The bands that are characteristic of shear-aligned cellulose liquid crystals [18] are not present in fibers with diameters under 1.2 mm. The high polymer concentration of the liquid-crystalline APC solution (60% w/w) tends to yield fibers with larger diameters; however, as is standard procedure in electrospinning, [19] the fiber diameter can be reduced by using higher voltages and lower flow rates.…”

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confidence: 91%

Helical Twisting of Electrospun Liquid Crystalline Cellulose Micro‐ and Nanofibers

et al. 2008

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Helical Twisting of Electrospun Liquid Crystalline Cellulose Micro‐ and Nanofibers

et al. 2008

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“…The resulting internal stress induces a periodical contraction, demonstrating itself in the ''serpentine'' or ''zig-zag'' undulation modes frequently observed after shear. The characteristic shear-band morphology is influenced by the precursor solution composition, solvent evaporation rate, film thickness, rate and duration of shear (Godinho et al 2002;Wang and Labes 1992;Mori et al 1999;Yan et al 2003). The scheme representing the polymer shear alignment and the formation of the banded microstructures is shown in Fig.…”

Section: Introductionmentioning

confidence: 99%

“…The scheme representing the polymer shear alignment and the formation of the banded microstructures is shown in Fig. 1, with the typically small director variation of approximately ± 10°b etween the adjacent bands (Godinho et al 2002;Wang and Labes 1992). Detailed measurements on the Fig.…”

Section: Introductionmentioning

confidence: 99%

Liquid crystalline cellulose derivative elastomer films under uniaxial strain

Godinho¹,

Filip²,

Costa³

et al. 2008

Cellulose

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Mesogenic cellulose derivative chains cross-linked into free-standing thin films were prepared by a shear-casting technique from anisotropic precursor solutions of thermotropic (acetoxypropyl) cellulose. After shear cessation a macroscopically oriented serpentine structure with the director in average along the shear direction is locked resulting in anisotropic optical and mechanical properties of the material. These films were submitted to an external uniaxial mechanical field perpendicular and parallel to the shear direction. Stretching perpendicular to the shear direction produced significant director rotations and a reset of order of the director order parameter for a deformation in the range 2-3 as detected by X-rays and optical microscopy. The different response found for strains imposed parallel and perpendicular to the initial average director orientation indicates that even though our system shows a serpentine director modulation that is either attenuated or reinforced by deformations parallel or perpendicular to the shear direction, its behaviour is similar to theoretical predictions for monodomain nematic elastomers described in the literature.

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“…It was found that a fine tuning of the surface properties of the solid cellulosic matrix can be achieved by varying their preparation conditions [17]. The influence of different matrix parameters upon the electro-optical behaviour of the cells was studied [18,19].…”

Section: Introductionmentioning

confidence: 99%

Tunable topographical cellulose matrices for electro-optical liquid crystal cells

Costa¹,

Almeida²,

Filip³

et al. 2006

Opto-Electronics Review

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In this work we have used acetoxypropylcellulose (APC) to produce free standing solid films (∼60 μm) that were used for assembling electro-optical devices. Thin films were obtained from concentrated lyotropic solutions of cellulose derivatives. Induced by the cast and shearing preparation conditions wrinkles and band textures can be observed in their free-surface plane. In order to eliminate and control these textures we used a process similar to that introducted in literature [1] which consists of storing the films in the same solvent-vapour atmosphere as the solution system. Lyotropic APC liquid crystalline solutions in dymethylacetamide (DMA) with crosslinker were prepared, thin films were obtained by using a shear/casting technique and stored in the solvent-vapour atmosphere until a planar structure was achieved. The dried crosslinked films were analyzed by optical polarised microscopy (POM) and scanning electron microscopy (SEM). The films with different topographies were used to produce optical cells composed by the cellulose derivative film covered on both free surfaces by a layer of the nematic liquid crystal E7 and placed between two transparent conducting substrates. The electro-optical properties of these cells were obtained.

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Atomic Force Microscopy Study of Hydroxypropylcellulose Films Prepared from Liquid Crystalline Aqueous Solutions

Cited by 46 publications

References 16 publications

Helical Twisting of Electrospun Liquid Crystalline Cellulose Micro‐ and Nanofibers

Helical Twisting of Electrospun Liquid Crystalline Cellulose Micro‐ and Nanofibers

Liquid crystalline cellulose derivative elastomer films under uniaxial strain

Tunable topographical cellulose matrices for electro-optical liquid crystal cells

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