Hydroxypropyl Cellulose Aqueous Solution Research Articles

Development of Environmentally Friendly Cellulose Derivative-Based Hydrogels for Contact Lenses Using a Radiation Crosslinking Technique

Although they have potential environmental pollution issues, soft contact lenses are value-added biodevices for medical use. Thus, it is important to reconsider starting materials and production methods to achieve sustainable development. In this study, hydrogels composed of hydroxypropyl cellulose (HPC) as an environmentally friendly material were produced by radiation and investigated for use in disposable soft contact lenses. HPC-based hydrogels with good mechanical properties and transparency were prepared by irradiation of electron beams on highly concentrated aqueous solutions containing HPC, polyethylene glycol #1000 dimethacrylate (23G), and 2-hydroxyethyl methacrylate (HEMA). The addition of 23G to HPC aqueous solutions resulted in an increase in the gel fraction as well as improved mechanical properties, such as tensile strength and elongation at break. The tensile strength and the elongation at break of HPC/HEMA/23G hydrogel obtained by the further addition of HEMA with HPC/23G aqueous solutions exhibited 0.2 MPa and 124%, which were approximately 2.0 and 1.8 times larger than these of the pure HPC hydrogel, respectively. The evaluation of the properties of the HPC/HEMA/23G hydrogel demonstrated its potential as a soft contact material with improved mechanical properties.

The role of the screw profile on granular structure and mixing efficiency of a high-dose hydrophobic drug formulation during twin screw wet granulation.

This study aimed at systematically investigating the role of distributive comb mixing element (GLC) and neutral dispersive mixing kneading block element (K90) on the structure and physical properties of granules containing high-dose of poorly water-soluble drug. Albendazole was used as the model drug at 50wt% drug loading. Lactose monohydrate and microcrystalline cellulose were used as diluent, and 3 w/v% hydroxypropyl cellulose aqueous solution was used as binder liquid. It was found that the use of GLC element resulted in formation of granules with higher internal porosity, more homogeneous binder distribution, smaller particle size, superior compaction properties and tabletability while K90 kneading element produced relatively larger and denser granules with less homogeneous binder distribution where binder was mainly concentrated in larger granules. The use of downstream GLC element was shown to result in an approximately 8% and 57% reduction in the D50 for 0.2 and 0.3 liquid-to-solid ratios, demonstrating a significantly higher sensitivity of granule size to screw profile at higher liquid-to-solid ratios. The axial mixing efficiency was assessed by measuring the residence time distribution of the granulation process with screw profiles containing K90 and GLC elements. It was found that granules had longer mean residence time and broader residence time distribution within GLC element due to enhanced backmixing and axial dispersion processes. The continuous "fragmentation-reagglomeration" cycle was proposed to be the main advantage of distributive GLC element in granulation of hydrophobic powders.

Properties of Composite Films of Hydroxyethyl Cellulose and Hydroxypropyl Cellulose with Poly-N-methyl-N-vinylacetamide

Composite films have been obtained from mixtures of hydroxyethyl cellulose and hydroxypropyl cellulose aqueous solutions with poly-N-methyl-N-vinylacetamide. The structural organization of composite films has been studied by dynamic mechanical analysis and X-ray diffraction analysis, and the composition ranges where cellulose ethers are compatible with synthetic polyamide and form mixed structural formations have been determined. The values of the solubility parameter and the surface energy of polymers have been compared with their compatibility in the solid state.

Effect of polymer concentration and thermal history on the inverse thermogelation of hydroxypropylcellulose aqueous solutions

We report on the inverse thermogelation of aqueous solutions of high molecular weight HydroxyPropylCellulose (HPC). The gelation process is investigated at different polymer concentrations, in the range 4÷16% (w/w). For each concentration, different heating rates are considered, in order to explore the effects on the sol-gel transition. Our findings corroborate the scenario proposed in literature for the thermoreversible gelation of cellulose derivatives, according to which the sol-gel transition is governed by an interplay of liquid-liquid phase separation and gelation. Gelation occurs in the polymer-rich phase via enhanced hydrophobic interactions between polymer chains at high temperature. At low heating rates, the phase separation proceeds significantly before the gelation occurs, creating more coarsened phases. As a consequence, the polymer network is less percolated and results in a weaker gel. Such an effect is more evident in less concentrated solutions characterized by a shorter terminal relaxation time, that is, faster polymer diffusion. As HPC concentration and heating rates are increased, the dissipative capacity of the final gel, expressed by the value of the phase angle at high temperatures, becomes nearly independent on polymer concentration and heating rate. However, the absolute values of the viscoelastic moduli of the formed gel increase with both HPC concentration and heating rate. The temperature window where transition occurs slightly narrows down with increasing concentration.

高分子溶液の平面急拡大流れにおける流動誘起配向に対する流体物性の影響

Flow-induced orientational changes of xanthan gum aqueous solutions and hydroxypropyl cellulose aqueous solutions in a planar channel with an abrupt expansion were examined by measurements of the flow-induced birefringence changes and velocity fields along the centerline of the channel. Four kinds of the xanthan gum (X-gum, Mw >2,000,000) solutions with different concentrations (0.45 0.5 0.7 0.9 wt%) and two kinds of the hydroxypropyl cellulose solutions with different molecular weights (HPC-M, Mw = 620,000 / HPC-H, Mw = 910,000) were tested in this experiment. Characteristic times were evaluated from G' and G" curves respectively. The birefringence changes were delayed corresponding to the characteristic times. Typical sizes of regions where the flow structure of polymers were affected by the abrupt expansion were estimated with the birefringence changes. The normalized sizes have a good correlation with a viscoelastic factor (apparent Weissenberg number) estimated in upstream region regardless of the concentrations of the solutions nor the polymer types.

PB35 ヒドロキシプロピルセルロース液晶の選択反射を用いた可変色表示デバイスの開発(フォトニクス・光デバイス,ポスター発表,2012年日本液晶学会討論会)

PB35 ヒドロキシプロピルセルロース液晶の選択反射を用いた可変色表示デバイスの開発(フォトニクス・光デバイス,ポスター発表,2012年日本液晶学会討論会)

Methacrylic acid-triggered phase transition behavior of thermosensitive hydroxypropylcellulose

Methacrylic acid (MAA)-triggered phase transition of thermosensitive hydroxypropyl cellulose (HPC) was studied. The phase transition temperature of 0.1wt.% HPC aqueous solutions was dramatically reduced from 41°C to 8°C as the MAA concentration increased from 0wt.% to 4wt.%. The sharp decrease of HPC phase transition temperature triggered by MAA may be attributed to strong hydrogen bonding between MAA and HPC. It may be proposed that the hydrogen bonding of MAA with HPC restricts the interaction of water with HPC and so reduces the solubility of HPC in water and improves the hydrophobic association of HPC. Furthermore, MAA attaching on HPC polymer chains was polymerized to form surfactant-free PMAA nanogels around ambient temperature when HPC collapsed forming PMAA nanogels. Effect of MAA concentration and polymerization temperature on the size and size distribution of PMAA nanogels was investigated.

Addition effects of imidazolium salts on mesophase structure and optical properties of concentrated hydroxypropyl cellulose aqueous solutions

Addition effects of N-alkyl-substituted methylimidazolium salts ([CnMim][X]) on the mesophase structure and lower critical solution temperature (LCST)-type phase-separation behavior of concentrated hydroxypropyl cellulose (HPC) aqueous solutions were investigated mainly by spectrophotometry. In the cholesteric mesophase formation, at concentrations of more than 50 wt% HPC, helical pitch (P) was confirmed to shift upward according to the chaotropic strength of X–, for example, in a manner satisfying the order of Cl−<Br−<NO3−<I−. Organocations generally elevated P relative to the nonionic reference, the effectiveness being pronounced in the order of [C2Mim]+<[C4Mim]+<[C6Mim]+. With regard to LCST behavior, imidazolium additives raised the cloud point (Tc) in the isotropic solutions of ⩽40 wt% HPC, whereas the Tc value of mesomorphic solutions was prone to be lowered by the addition. Discussion of these observations took into consideration the differences in the N-alkyl structure and amphiphilic nature between cationic imidazolium varieties, as well as the difference in the chaotropic strength between the counter anions. It was also exemplified preliminarily that this kind of salt-containing lyotropic system of HPC exercised an electro-optical function when coupled with an electric circuit. Addition effects of a series of N-alkyl-substituted methylimidazolium salts ([CnMim][X]) on the mesophase structure and LCST-type phase-separation behavior, and the ensuing optical properties of concentrated hydroxypropyl cellulose (HPC) aqueous solutions, were investigated by spectrophotometry and complementary X-ray diffractometry. Salted HPC solutions exhibited distinct shifts in both the cholesteric pitch and the cloud point, relative to the nonionic reference. Discussion of the observations took into consideration the differences in the N-alkyl structure and amphiphilic nature between the imidazolium varieties, as well as the difference in a socalled chaotropic strength between the anions used.

Preparation of Cholesteric (Hydroxypropyl)cellulose/Polymer Networks and Ion-Mediated Control of Their Optical Properties

(Hydroxypropyl)cellulose (HPC)/vinyl polymer networks were synthesized in film form from liquid-crystalline solutions of HPC in a mixed solvent of methacrylate monomer/methanol/water (2:1:2 in weight) containing cross-linking agents, via photopolymerization of the methacrylate monomer. Di(ethylene glycol) monomethyl ether methacrylate (DEGMEM) or 2-hydroxypropyl methacrylate (HPMA) was used as the polymerizing monomer, and tetra(ethylene glycol) diacrylate and glutaraldehyde were the cross-linkers for the monomers and HPC, respectively. The polymer composite films, HPC/PDEGMEM and HPC/PHPMA, prepared at ca. 60-70 wt % concentrations of HPC in the starting solutions, were iridescently colored due to the selective light reflection, originating from the cholesteric helical arrangement carried over successively into the network system. When the cholesteric films were immersed and swollen in water containing an inorganic neutral salt, their coloration and optical turbidity varied according to a strength of 'chaotropicity' of the impregnant ions. This ionic effect may be interpreted as essentially identical with that found formerly in the coexistent salt-sort dependence of the cholesteric pitch and lower critical solution temperature for HPC aqueous solutions. It is also demonstrated that visual appearance of the swollen networks can be changed by application of an electric potential of practical magnitude between both edges of the samples of rectangular shape.

Selective Reflection of Hydroxypropyl Cellulose Prepared with Autoclave

A hydroxypropyl cellulose (HPC) aqueous solution has been attracting attention as an electrically color-changeable reflector. The purpose of this study is to shorten the preparation time of HPC aqueous solution. By the conventional method, preparation takes more than three weeks, because the HPC solution has a high viscosity. We provide a novel preparation method for HPC aqueous solution using an autoclave. The preparation duration was shortened to only three days. The uniformity of the selective reflection and reproducibility of the cell were also evaluated in this study.

ITO properties on anisotropic flexible transparent cellulosic substrates under different stress conditions

Cellulose derivatives have been actively investigated as flexible transparent substrates for liquid crystal display (LCD) technology. Working electronic devices deposited on flexible substrates are subject to deformation and external stress. Hydroxypropylcellulose (HPC) solid films (20–60 μm) obtained from aqueous liquid crystalline solutions present tunable topography. Substrates with anisotropic topography were obtained by casting and shearing a 65% (w/w) HPC aqueous solution (HPC-65). Two types of periodicity were observed by atomic force microscopy (AFM). A primary set of large bands, perpendicular to the shear direction (1.8–2.1 μm periodicity and 74–87 nm average peak-to-valley height) was found. A secondary smoother band texture (0.35–0.40 μm periodicity and 2.9–4.4 nm average peak-to-valley height) lies under the large bands. The resistivity of indium tin oxide (ITO), deposited on these flexible anisotropic substrates (HPC-65/ITO) under different stress conditions, was studied. These stress conditions were originated by folding the films around tubes with decreasing diameter (45–5 mm). The folding was performed along two directions. One direction was chosen with the tube axis along the shear direction (FB1). Another direction was chosen with the tube axis perpendicular to the shear direction (FB2). The resistivity of ITO films submitted to FB1 folding does not change significantly with the tube diameter, nor after release neither after overnight relaxation. The resistivity of ITO films submitted to FB2 folding increases strongly and the films become insulating for tubes with diameter lower than 10 mm. AFM measurements show that this anisotropic behavior is induced by cracks in the ITO coatings. These cracks appeared mainly along the secondary set of bands found in anisotropic substrates.

Band-texture decorated spatial distribution of molecular orientation around air bubbles in hydroxypropyl cellulose aqueous solution

The air bubbles in the concentrated hydroxypropyl cellulose (HPC) aqueous solution have been employed to monitor the spatial distribution of molecular orientation around spherical or ellipsoidal particles within the liquid crystalline matrix. The deformation of the air bubbles under shear flow was observed in a polarizing microscope. The stream lines are curved near air bubbles. Corresponding spatial distribution of the molecular orientation was revealed by the technique of band-texture decoration. Associated pleated morphology was also observed in a scanning electron microscope.

Hydrostatic pressure effects on polymer cholesteric liquid-crystalline structure. I. Equilibrium structure of hydroxypropyl cellulose aqueous solution

Abstract The effect of pressure on the polymer cholesteric liquid-crystalline structure of hydroxypropyl cellulose aqueous solutions was studied using reflection spectra measurements. Pressures applied to the polymer liquid crystals ranged from 1 to 2000 bar. The equilibrium reflection spectrum of the cholesteric structure shifted to longer wavelengths, showing that the cholesteric pitch of the liquid-crystalline structure increases as the applied pressure increases. At pressures higher than 200 bar the maximum wavelength of reflection shifted linearly with the increase in applied pressure. At lower pressures, the cholesteric structure was influenced by the surface plane of the quartz window.