Hydroxypropylcellulose Concentration Research Articles

Salting-in behavior of isotropic and anisotropic aqueous hydroxypropylcellulose solutions

Salts with large polarizable ions are capable of salting-in complex aqueous polymer solutions exhibiting microstructure, thereby inducing changes in the phase behavior and properties of the solutions. In this work, the dynamic rheological properties of isotropic and mesomorphic hydroxypropylcellulose (HPC) in aqueous media have been investigated in the presence of one such salt, guanidine thiocyanate (GuSCN). Addition of this salt to isotropic aqueous HPC solutions is found to induce an increase in the magnitude of the elastic shear modulus (G′). At HPC concentrations above the isotropic → mesophase transition, however, addition of GuSCN results in a substantial reduction in G′ due to microstructural changes in the chiral nematic HPC mesophase. This reduction in G′ indicates that the microstructure of a water-soluble polymer exhibiting supramolecular organization can be tailored through salting-in, and is likewise expected to facilitate the commercial processing of HPC at high solids concentrations.

Enhancement of in vivo anti-influenza virus activity of 5,7,4'-trihydroxy-8-methoxyflavone by drug delivery system using hydroxypropyl cellulose.

Enhancement of in vivo antiviral activity of 5,7,4'-trihydroxy-8-methoxyflavone (F36) against H3N2 subtype of influenza A virus by drug delivery system (DDS) with hydroxypropyl cellulose (HPC) was studied. Although in the absence of HPC F36 (0.5 mg/kg) showed no antiviral activity against mouse-adapted influenza virus A/Guizhou/54/89 (H3N2) in mice, when F36 solution containing HPC was administered intranasally 5 min after the virus inoculation, proliferation of the virus in both nasal and broncho-alveolar cavities was inhibited significantly. The relationship between concentration (0.2-0.5%) and deposition ratio of HPC was studied. When 10 microliters of fluorescein isothiocyanate (FITC)-conjugated HPC solution was administered intranasally to BALB/c mice, deposition ratio of HPC at 6 h after inoculation in nasal cavity was dependent on its concentration. The deposition ratio of HPC in broncho-alveolar cavity, however, was reversely dependent on its concentration. Anti-influenza virus activity of F36 in nasal and broncho-alveolar cavities was dependent both on the concentration and deposition ratio of HPC. HPC was most effective at 0.5% in nasal cavity and at 0.3% in broncho-alveolar cavity. These results indicate that DDS with HPC enhances the anti-influenza virus activity of F36 in vivo.

持続性塩酸オキシブチニンぼうこう内注入液の製剤化とその評価

We developed a prolonged-action oxybutynin hydrochloride (OB) solution (5 mg/10 ml) for intravesical instillation therapy in the treatment of refractory urinary incontinence in neuropathic bladder disease. Hydroxypropylcellulose (HPC) was selected as a viscosifying agent. The OB solution containing HPC (HPC-OB solution) exhibited Newtonian viscosity. Although the release of OB from the HPC-OB solution was retarded by an increase in the HPC concentration, the apparent release rate constant was scarcely affected by solutions with more than a 1.0% HPC. Based on these findings, the optimal concentration of HPC was thus selected to be 1% in pharmaceuticals as a viscosifying agent. The pH of the HPC-OB solution containing 1% HPC was 5.94 and was stable for 6 months under all storage conditions. OB was stable under cold-dark conditions for 6 months. However, the residual content of OB was 94.8 and 95.1% after 6 months storage at room temperature under light and dark conditions, respectively.The urine concentrations of OB after a single intravesical instillation of OB (5 mg/10 ml) were also evaluated. The amount of urine excretion of OB after HPC-OB solution was significantly lower than that after OB solution at first urination. The total amount of urine excretion of OB after HPC-OB solution thus appeared to be low compared with that after OB solution. These results thus suggest that OB may remain intravesically after the instillation of HPC-OB solution for a longer period than that of OB solution.In conclusion, based on the above findings the use of intravesical HPC-OB solution is thus considered to be a more practical procedure than the use of OB solution for controlling incontinence in neuropathic bladder disease.

Effect of formation of surface complex between hydroxypropylcellulose and sodium dodecylsulfate on dispersion/flocculation of O/W-type emulsion of soybean oil

An O/W-type emulsion of soybean oil (theta v = 0.05) was prepared in the presence of various concentrations of hydroxypropylcellulose (HPC) and sodium dodecylsulfate (SDS). The mean diameter (d) of secondary particles of the oil droplets decreased with concentrations of SDS and HPC after attaining a maximum at [SDS] = 5 mmol/dm3 and [HPC] = 10(-3) g/dl, while the relative viscosity (eta rel) of the emulsion increased with an SDS concentration after attaining a minimum around 5 mmol/dl3 when the HPC concentration was kept constant. These facts were explained in terms of the formulation of a surface complex by hydrophobic interaction between SDS and HPC adsorbed on the surface of the droplets. When the concentration of SDS is low, it bridges between the HPC segments intra- and intermolecularly on and between the particles, resulting in shrinking of the HPC surface layers as well as in bridging among the particles. Therefore, the total volume of the secondary particles effective on eta rel decreases while the d-value increases with the SDS concentration. When the concentration becomes high, binding ratio of SDS to HPC also increases and the segments are repulsive each other owing to the negative charges given by the bound SDS. As a result, the adsorption layer swells and the secondary particles are redispersed. This fact causes an increase in eta rel and a decrease in d-value with a concentration of added SDS.

Swelling Dynamics of Cross-Linked Poly(acrylic acid) and Neutralized Poly(acrylate-co-acrylic acid) in Aqueous Solutions of (Hydroxypropyl)cellulose

When a polyelectrolyte gel is placed into a (hydroxypropyl)cellulose (HPC) solution, there is a change in the local HPC concentration around the swelling particle. The HPC concentration profile development around the swelling gel is recorded as a function of time by optical microscopy, using a novel technique involving an isotropic-to-anisotropic phase transition, with a spatial resolution of a few microns. Using this technique the kinetics of swelling of poly(acrylic acid) (PAAc) and neutralized poly(acrylate-co-acrylic acid) (PAA) gels when placed in aqueous (hydroxypropyl)cellulose solutions and the HPC concentration redistributions in these systems were studied. A 75% neutralized PAA gel swells by sorbing mainly water, leaving HPC outside. At the beginning of the swelling, the HPC concentration gradient can be as high as 2% μm-1, with a transient HPC concentration of 80%. By contrast, in the case of the PAAc gel, the HPC concentration inside the particle is greater than outside at equilibrium. The final equilibrium is attained in two steps. During the first the solvent penetrates into the particle, producing a large temporary increase of HPC concentration outside the gel. During the second step HPC slowly penetrates the hydrogel, due to preferential interactions between PAAc and HPC, as shown by capillary viscometry for the corresponding linear polymer mixtures.

Preparation of Self-Coloring Cholesteric Films Based on Crosslinked Hydroxypropyl Cellulose.

In order to obtain the basic data for preparation of self-coloring cholesteric films based on crosslinked hydroxypropyl cellulose (HPC). we prepared the HPC liquid crystalline solution and investigated the effects of HPC concentration, temperature and addition of surfactant on the wavelength of reflective light (λ) by spectrophotometry in the concentration range of 58 to 66wt%. The value of λ decreased with HPC concentration and increased with temperature. The pitch of cholesteric helix (P) was derived from measurements of mean refractive indices and of λ. The dependence of P on the HPC concentration (Cv, in volume fraction) was investigated at 20°C; The reciprocal of P was proportional to Cv427 in the region below Cv=0.57, whereas that was proportional to Cv2.35 in the region above Cv=0.57. The power index also depended on the temperature.Regardless of the surfactant type (anionic, cationic and nonionic), the effect of surfactant on the value of λ depended on the HPC concentration and temperature.The homogeneous blue and heterogeneous red solid films could be cast and the color of films strongly depended on the cast conditions. The self-coloring solid films should be prepared at higher temperature.

Rheological differences among liquid‐crystalline polymers. II. Disappearance of negative N1 in densely packed lyotropes and thermotropes

The steady‐state viscosities η and first normal stress differences N1 as functions of the shear rate γ are measured for highly concentrated and densely packed solutions and melts of hydroxypropylcellulose (HPC) and a polyester [OQO(OEt)10] made from the condensation of 1,10‐decane‐bis‐benzoyl chloride and ethoxy substituted hydroquinone. As the concentration of HPC is increased, systematic departures from the predictions of the Doi theory are found. First, beginning at a concentration C of around 30% by weight, the zero‐shear viscosity begins to increase, rather than decrease, with increasing concentration. Then, at a concentration of 35%, the shear rate γmax at which N1 reaches a local maximum begins to decrease, rather than increase, with concentration, the viscoelastic activation energy of the solution begins to exceed that of the solvent, and the shape of the curve of N1 versus shear rate begins to become temperature sensitive. At a concentration of 55% at room temperature, the region of negative N1 disappears, although a local minimum of N1 remains. Finally, for bulk samples of HPC at elevated temperatures and for 60% solutions and bulk samples of [OQO(OEt)10], N1 is positive only, with no local minimum. We hypothesize that this progressive breakdown in the predictions of the Doi theory as concentration increases is caused by polymer–polymer hindrances to translational motion that at high concentration can only be relieved by increasing the temperature and thereby increasing the flexibility of the molecules.

Local structural correlations in anisotropic aqueous solutions of hydroxypropyl cellulose

Wide-angle X-ray scattering procedures are utilized to study the local structure of isotropic and anisotropic aqueous solutions of hydroxypropyl cellulose (HPC). The X-ray scattering data for a systematic series of solutions with 0–100% w/v HPC are reported and these curves show distinct and significant variations as the concentration of HPC is increased. In particular, a diffuse scattering peak whose position ( s ∼ 0.34−0.54 A ̊ −1 ) is composition dependent, develops in parallel with the formation of the anisotropic liquid crystal phase. There is no evidence to support the concept of clusters of HPC molecules in the anisotropic phase. The variations in peak positions and the synergistic nature of the scattering suggests that the water is largely associated with each HPC chain.

Coagulation kinetics of amorphous colloidal silica suspensions with and without hydroxypropyl cellulose polymer

The coagulation rate constant of submicron silica has been measured as a function of solution pH, salt concentration and hydroxypropyl cellulose (HPC) polymer concentration. Results show that the colloidal stability of silica is dominated by the cation concentration in the presence of salt in the pH range 3–9.5. The stability increases as cation concentration decreases. At low salt concentration and a minimum colloid stability was found in the intermediate pH range 4–8. These results show that differences in the literature values of the critical coagulation constant by relative light-scattering experiments can be explained by the use of the coagulation rate constant analysis. When HPC polymer was present in the solution, the colloid stability of the silica increased. The adsorption of polymer stabilizes the silica suspensions, both at low pH near the isoelectric point and at high ionic strength where it coagulates without the polymer. A monolayer coverage was necessary to provide steric stabilization. At 10−3 M KCl a smaller equilibrium concentration of HPC in solution is needed to give monolayer coverage and steric stabilization than at 1 M KCl and pH 4.2.

The Interaction of Sodium Dodecylsulfate with (Hydroxypropyl)Cellulose

(Hydroxypropyl)cellulose (HPC) in aqueous solution interacts with sodium dodecylsulfate (SDS) to give micelle-like SDS clusters bound to the polymer at concentrations well below the critical micelle concentration of SDS itself. We have used the steady-state fluorescence quenching method (fluorophore: pyrene, quencher: benzophenone) to determine mean aggregation numbers (N̅, molecules of SDS per cluster) for the system. These N̅ values vary with both surfactant and HPC concentrations. The data are consistent with a constant number of cluster binding sites per polymer. These clusters increase in size as the ratio of SDS to HPC is increased. This behavior is very different from that described for the interaction of SDS with poly(ethylene oxide).

Heats of dilution of water-soluble-polymer solutions (II) - heat interaction parameters of aqueous hydroxypropylcellulose and gelatin solutions determined by means of flow microcalorimeter

In order to obtain information about the intermolecular interaction between the water-soluble-polymers, we measured the heats of dilution of hydroxypropylcellulose(HPC)-water and gelatin-water systems at 298K by the flow microcalorimeter. The heat of dilution for gelatin-water system proved to be exothermic and the heat interaction parameter x 1, determined by Van Laar equation was estimated to be about −1.00. However, the heat of dilution of HPC-water system moves from the exothermic to the endothermic with an increase of HPC concentration and x 1-value in dilute solution was estimated to be about −0.91. We found that the interaction between gelatin and water depends linearly on the gelatin concentration, but for HPC-water system, the interaction depends considerably on the HPC concentration. From the results of these interactions, the hydrophilic effect of these water-soluble-polymers for water was the order of gelatin > HPC. We will discuss the hydrophilic and hydrophobic interactions from the results of heats of dilution.

Synthesis of monodisperse Ta2O5 powder

Narrow-sized, unagglomerated and spherical Ta2O5 powder was prepared by the controlled hydrolysis of tantalum pentaethoxide, Ta(OC2H5)5, in ethanol with a dispersant (hydroxypropyl cellulose) present. X-ray diffraction results showed that the as-prepared powder was amorphous and became crystalline after firing at 800° C in air for 2h. The particle size and the degree of agglomeration decrease with increasing hydroxypropyl cellulose concentration.

Diffusion of latex spheres through solutions of hydroxypropylcellulose in water

Translational diffusion coefficients of polystyrene latex spheres in solutions of hydroxypropylcellulose (HPC) have been measured using dynamic light scattering. As observed by other workers, latex clustering occurs, involving a bridging interaction of adsorbed HPC, which can be prevented using the nonionic surfactant Triton X-100. In the presence of Triton X-100, the diffusion data serve to test hydrodynamic theories of the Brownian motion of inert spheres in a matrix of entangled polymer chains. As predicted by certain theories, the diffusion data follow a stretched exponential function of the HPC concentration. For two HPC fractions of low molecular weight, we find that probe diffusion coefficients follow the Stokes-Einstein (SE) law, determined by the bulk viscosity of the HPC solution. For two fractions of high-molecular-weight HPC, the microviscosity measured by the SE equation is substantially smaller than the bulk viscosity. Within experimental error, the latter data follow the stretched exponential law D/ D 0 = exp[ α( C ν - C + ν )] with α ∝ M σ R ϵ , where ϵ = 0.7 ± 0.1, σ = 0.8 ± 0.1, and ν = 1.0. The characteristic concentration C + is numerically comparable to incipient overlap of the chains in a hexagonal close-packing arrangement. These results are discussed in terms of different theoretical models for the diffusion of spherical particles through a polymer matrix.

Rheological Effect of Excess Polymer on Latex Suspension

Abstract Effects of free polymers (Hydroxy–Propyl–Cellulose (HPC)) on the flocculation/dispersion feature of latex dispersions stabilized sterically by the same HPC at its lower critical solution temperature(ca. 50 °C) have been investigated from a view point of rheology. The observed curves of relative viscosity of the system under a lower shear rate have a peak about the concentration of free HPC, which depends on the molecular weight of added HPC. These experimental results indicate that, after saturated adsorption, the free HPC molecules induce the dispersion to flocculate in spite of the dense adsorbing layer of HPC on the particles which would tend to give rise to a steric stabilization. This behaviour is interpreted to be a result of depletion effect.

Interactions between polystyrene latex spheres and a semiflexible polymer, hydroxypropylcellulose

Shear viscosity has been measured for aqueous solutions of hydroxypropylcellulose (HPC) having molecular weight 292,000 in the concentration range 0–4% by weight. Additionally, the diffusivities, D. of latex spheres with diameters of 794 and 1814 Å suspended in these solutions were measured by dynamic light scattering. As HPC concentration was increased, the initial effect on D was a decrease of about 50% due to adsorption of HPC and “bridging” of the latex spheres by the HPC to form clusters. At higher HPC concentrations, the cluster diffusivities approximately follow a stretched exponential form, D = e − αw v , where w is the HPC weight fraction, but the significance of this result is limited in the present case. The diffusivities were essentially independent of scattering vector over the measured range. The microviscosities calculated from η μ = kT 6πDR exceeded the shear viscosities, η, from cone and plate and capillary measurements. However, this appears to be the result of the initial absorption/bridging to form clusters. If the cluster sizes are used to recalculate the microviscosities, then agreement between the micro- and the macroviscosities is found, within error, over almost three decades of viscosity. The clustering process was defeated by the addition of small amounts of a nonionic surfactant, regardless of the order of mixture of HPC, latex, and surfactant. The diffusivities of these bare spheres in solutions containing up to 0.1% HPC were measured and the microviscosities agreed reasonably well with the macroscopic viscosities, the maximum deviation being about − 12%.

Formation of ordered phases of (hydroxypropyl)cellulose in miscible and immiscible isobutyric acid‐water mixtures

Abstract(Hydroxypropyl)cellulose (HPC) is known to form birefringent liquid‐crystalline phases at elevated polymer concentrations in either water or isobutyric acid (IBA). The HPC concentration at which the polymeric phase exhibits birefringence decreases as the IBA content in mixed H2O/IBA solvents decreases, even though the concentration ϕic for the formation of an ordered phase of HPC in water is greater than that in IBA. Water is a spectator component and apparently does not participate in the formation of a birefringent phase when IBA is present. A birefringent phase forms once the concentration of HPC in the solution omitting the H2O equals the ϕic of binary HPC/IBA solutions for temperatures from 23 to 95°C. The strong preferential affinity of HPC for IBA is visually evident as an HPC coagulate separates from dilute solution when the solvent mixture contains as little as 5% IBA. The coagulate dissolves to give a monophasic isotropic solution as the IBA content in the solvent is increased. A heterogeneous system in which a clear supernatant fluid covers a pearly white polymeric phase forms when the solvent mixture is immiscible and the HPC content is less than 50%. At high HPC content, the classical appearance associated with concentrated HPC solutions is seen. The optical and rheological properties of the heterogeneous systems are compared with those of homogeneous solutions at several HPC concentrations.

Effect of in Situ Polymer Adsorption on the Synthesis of Monodisperse Tio2 Powders

ABSTRACTMonodisperse and spherical titania powders were prepared by the hydrolysis of titanium tetraethoxide in ethanol with hydroxy-propyl cellulose(HPC) present during particle precipitation. The mean particle size decreased as the concentration of tLPC increased. The critical concentration of HPC for the in situ stabilization of titania powder suspensions was determined by a photographic method, and found to be independent of the molecular weight of HPC within the molecular range of 60,000 to 300,000. The amount of HPC adsorbed on the particle surface, determined by a colorimetric method using a UV-visible spectrophotometer, decreased with the increasing molecular weight of HPC. Suspension stability was confirmed by theoretical calculations based on experimental results.

Pilocarpine release from hydroxypropyl-cellulose-polyvinylpyrrolidone matrices

Characteristics of pilocarpine release from cast plasticized hydroxypropylcellulose (HPC) and HPC-polyvinylpyrrolidone (PVP) matrices were studied using tritiated pilocarpine. Increased concentration of PVP and decreased molecular weight of HPC accelerated release of pilocarpine from the matrices. The aqueous solution penetrated rapidly into the matrices, which swelled rapidly to their equilibrium volumes. With increased molecular weight and concentration of HPC in the matrices, the rate of solvent penetration decreased and swollen volume of the matrix increased. Pilocarpine concentration also decreased in the ungelled cores of the matrices, indicating that the solvent had penetrated these cores. Solvent penetration alone did not control the rate of drug release, because penetration was at least twice as rapid as pilocarpine release. In the matrices without polymer dissolution, the best fits of the release data were obtained with diffusional square-root of time dependence, although relaxation of the polymers caused slight deviations from the Fickian diffusion. Thus the rate-limiting step of pilocarpine release was the diffusion of the drug from the matrix. The decreased rate of pilocarpine release with increased molecular weight and concentration of HPC was due to the decreased rate of drug diffusion from the matrix. Retardation of this diffusion was caused by the increased swelling of the matrix and decreased diffusivity of the drug. High initial concentration of PVP resulted in substantial deformation and attrition of the matrices.

Ultrasonic Degradation of Hydroxypropyl Cellulose Solutions in Water, Ethanol, and Tetrahydrofuran

Abstract Ultrasonic degradations of hydroxypropyl cellulose (HPC) have been carried out in water, ethanol, and tetrahydrofuran (THF) solutions. In the HPC-water system, cavitation intensity did not increase linearly with ultrasound intensity because of a lower threshold of ultrasonic intensity below which cavitation does not occur. At 27°C the rate of degradation in the three solvents followed the order water > ethanol > THF which is not in line with their characteristic impedance values. The rate of degradation for 20 kHz, 70 W ultrasound intensity was found to increase with a decrease in solution volumes, concentration of HPC, and temperature. Increased rate of degradation at lower temperatures supports the concept based on sonoluminescence experiments that it is the cavitation in a polymer solution that is responsible for ultrasonic degradations and the dissolved polymer molecules do not act as cavitation nuclei. Increased surface tension and density of the solvent are thought to be responsible for imp...

Diffusion transport of sucrose, ß-alanine and bovine serum albumin in aqueous solutions of hydroxypropyl cellulose

Diffusion of sucrose, ß-alanine and bovine serum albumin has been studied in moderately concentrated aqueous solutions of hydroxypropyl cellulose (HPC), both at 25° (good solvent conditions) and at 36° (approaching theta solvent conditions). For sucrose, the diffusion rate is almost independent of the concentration of HPC. For the two other diffusants, the diffusion rate decreases significantly when the concentration of HPC is increased; the decrease is more pronounced at 36° than at 25°. The results are discussed qualitatively in the light of recent theoretical models.