Capillary rheometry of lyotropic liquid crystals of hydroxypropyl cellulose

Suto, Shinichi; Ohshiro, Masahiko; Ito, Ryoko; Karasawa, Mikio

doi:10.1016/0032-3861(87)90314-4

Cited by 17 publications

(3 citation statements)

References 12 publications

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“…Generally k' can be taken as a measure of the interaction between polymer molecules. Therefore, when a molecule extends or solvation occurs, k' decreases.16 Figures 2,3,and 4 show that the role of NaCl or LiCl is quite different from that of thiourea. Some investigat~rs'~-~~ have been reported the effects of salt on T, and [ q ] of various nonionic polymers in aqueous media; NaCl and LiCl have been known as a water-structure maker and thiourea as a water-structure breaker.…”

Section: Resultsmentioning

confidence: 94%

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior

Suto

Nishibori

Kudo

et al. 1989

J of Applied Polymer Sci

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SynopsisEffect of addition of salt on the viscometric behavior of the dilute or concentrated aqueous solution of hydroxypropyl cellulose (HPC) was determined by means of an Ubbelohde or a cone-plate viscometer. That effect on the turbidity of the dilute system was also determined. As salts, NaC1, LiCl, and thiourea were chosen. The turbidity and viscometric behavior for the dilute system, and the viscometric behavior for the concentrated system were greatly affected by salt type and concentration. With increasing NaCl or LiCl concentration, the cloud point decreased,[el showed a maximum, Huggins' constant k' showed a minimum, and the shear viscosity for concentrated isotropic solutions showed a maximum. The 45 wt % solution with no salt showed a viscometric behavior which was characteristic of lyotropic liquid crystals; however, with increasing NaCl concentration, a critical temperature at which the shear viscosity showed a maximum with respect to temperature shifted to lower temperature. This behavior was due to an increase in the turbidity, not due to a phase transformation. On the other hand, an addition of thiourea did not affect so greatly the turbidity and viscometric behavior as an addition of NaCl or LiCl did. We speculated different actions of NaCl and thiourea.

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Section: Resultsmentioning

confidence: 94%

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior

Suto

Nishibori

Kudo

et al. 1989

J of Applied Polymer Sci

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“…3,4,23 Cellulosic liquid crystals form the cholesteric order, although some derivatives exhibit left-handedness and some exhibit right-handedness. We suggest that the cholesteric order is the key factor for the cellulosic liquid crystal to exhibit the greater S R and die swell.…”

Section: Model For Greater S Rmentioning

confidence: 99%

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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“…Therefore, HPC depicts organic as well as water solubility and hence is suitable for solvent methods to manufacture SDs (19). In addition, it also has lower critical solution temperature of 45°C due to the presence of both hydrophilic and hydrophobic groups and forms liquid crystals and many other mesophases in water, depending upon concentration (20)(21)(22). Such liquid crystalline phases may form gel-like layers associated with hydrated HPC formulation to control the release of highly water-soluble drugs (23).…”

Section: Introductionmentioning

confidence: 99%

Low-Viscosity Hydroxypropylcellulose (HPC) Grades SL and SSL: Versatile Pharmaceutical Polymers for Dissolution Enhancement, Controlled Release, and Pharmaceutical Processing

Sarode

Wang

Cote³

et al. 2012

AAPS PharmSciTech

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Abstract. Hydroxypropylcellulose (HPC)-SL and -SSL, low-viscosity hydroxypropylcellulose polymers, are versatile pharmaceutical excipients. The utility of HPC polymers was assessed for both dissolution enhancement and sustained release of pharmaceutical drugs using various processing techniques. The BCS class II drugs carbamazepine (CBZ), hydrochlorthiazide, and phenytoin (PHT) were hot melt mixed (HMM) with various polymers. PHT formulations produced by solvent evaporation (SE) and ball milling (BM) were prepared using HPC-SSL. HMM formulations of BCS class I chlorpheniramine maleate (CPM) were prepared using HPC-SL and -SSL. These solid dispersions (SDs) manufactured using different processes were evaluated for amorphous transformation and dissolution characteristics. Drug degradation because of HMM processing was also assessed. Amorphous conversion using HMM could be achieved only for relatively low-melting CBZ and CPM. SE and BM did not produce amorphous SDs of PHT using HPC-SSL. Chemical stability of all the drugs was maintained using HPC during the HMM process. Dissolution enhancement was observed in HPC-based HMMs and compared well to other polymers. The dissolution enhancement of PHT was in the order of SE>BM>HMM>physical mixtures, as compared to the pure drug, perhaps due to more intimate mixing that occurred during SE and BM than in HMM. Dissolution of CPM could be significantly sustained in simulated gastric and intestinal fluids using HPC polymers. These studies revealed that low-viscosity HPC-SL and -SSL can be employed to produce chemically stable SDs of poorly as well as highly water-soluble drugs using various pharmaceutical processes in order to control drug dissolution.

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Capillary rheometry of lyotropic liquid crystals of hydroxypropyl cellulose

Cited by 17 publications

References 12 publications

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior

Lyotropic liquid crystalline solutions of hydroxypropyl cellulose in water: Effect of salts on the turbidity and viscometric behavior

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

Low-Viscosity Hydroxypropylcellulose (HPC) Grades SL and SSL: Versatile Pharmaceutical Polymers for Dissolution Enhancement, Controlled Release, and Pharmaceutical Processing

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