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Hydration of Hydroxypropylmethyl Cellulose: Effects of pH and Molecular Mass

100%

Tritt-Goc J., Kowalczuk J., Piślewski N.

Acta Physica Polonica A

2005

vol. 108

issue 1

197-205

Magnetic resonance imaging was used to study the diffusion of a water solution of hydrochloric acid (HCl) and sodium hydrochloride (NaOH) into hydroxypropylmethyl cellulose matrices. Polymer in the form of a cylinder was hydrated in a water solvent of pH = 2, 7, and 12 at 37ºC and monitored at equal intervals with a 300 MHz Bruker AVANCE. The spatially resolved spin-spin relaxations times and spin densities, along with a change in the dimension of the glass core of the polymer were determined for hydroxypropylmethyl cellulose tablets as a function of hydration times. The data showed the effects of the pH solvent and of the molecular mass of the polymer on the swelling process, spin-spin relaxation time, and diffusion of solvent molecules into hydroxypropylmethyl cellulose matrices. The time dependence of the diffusion front, effective T_2, and proton-density ρ analysis clearly indicate a case II diffusion mechanism in the system composed of a water solution of hydrochloric acid (pH = 2) and hydroxypropylmethyl cellulose, whereas in the case of water solutions with pH = 7 and 12 the anomalous and case I diffusion are observed, respectively.

Gelation Process of Toluene-Based bis-Urea in Cyclohexane Studied with Magnetic Resonance Imaging

80%

Tritt-Goc J., Boguszyńska J., Szwaj M., Boutellier L., Jadżyn J.

Acta Physica Polonica A

2005

vol. 108

issue 1

81-87

Magnetic resonance imaging was used for studies of the gelation and swelling processes of toluene-based bis-urea prepared in a form of cylindrical tablet and immersed in cyclohexane. The processes were investigated with the use of Bruker AVANCE (300 MHz) spectrometer equipped with a micro imaging probe head. The images were taken for cyclohexane protons within the bis-urea gel formed around the sample dry core at different intervals of the immersion. The mobility of the solvent molecules was estimated from the spatially resolved distribution of the spin-spin relaxation time T_2 and the spin densitiesρ, calculated on the basis of the images obtained. It was shown that the time-evolution of the thickness of the gel layer can be well described by the power equation with an exponent equal to 0.47 (±0.04), indicating the Fickian nature of the diffusion of cyclohexane molecules.

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2 Acta Physica Polonica A

2 2005

2 Tritt-Goc J.

1 Boguszyńska J.

1 Boutellier L.

1 Jadżyn J.

1 Kowalczuk J.

1 Piślewski N.

1 Szwaj M.

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Hydration of Hydroxypropylmethyl Cellulose: Effects of pH and Molecular Mass

Gelation Process of Toluene-Based bis-Urea in Cyclohexane Studied with Magnetic Resonance Imaging