Water-Induced Charge Transport in Microcrystalline Cellulose

Microcrystalline cellulose (MCC) is the most frequently used excipient for direct compaction of tablets within the pharmaceutical industry. It has earlier been indicated that the interactions between the hydration shell – surrounding the drug molecules in an MCC tablet – and the cellulose regulate the speed of the drug release process. These interactions, and the charge transport governed by moisture, are therefore important to analyze and understand to be able to tailor make new functional drug delivery systems.In this thesis the physical parameters affecting the water-induced ionic transport have been studied with impedance spectroscopy, transient current measurements, nitrogen adsorption and scanning electron microscopy…


Background on the Cellulose structure
Water in cellulose
Charge transport in cellulose: Earlier findings
Power-law model
Exponential model
Charge transport at zero moisture content
Charge transport percolation theory
Experimental methods and materials
Electrical methods
Impedance spectroscopy and dielectric response
Transient current measurements
The sample cells and electrodes
Gas Adsorption
Equipment and measurement procedure
Fractal dimension determination from the capillary condensation region
Scanning Electron Microscopy
Results and discussion
Generalized regular singular-points
Dielectric relaxations
The high-frequency relaxation
The low-frequency wet relaxation
Cole-Cole parameters
DC conduction
Charge carrier density
The effect of pore structure on dc conduction
Summary and conclusion
Summary of appended papers
Summary in Swedish

Author: Nilsson, Martin

Source: Uppsala University Library

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