Rheological properties and diffusion dissolution behaviour of hydrophilic polymers

Area of Science:

• Polymer Science
• Materials Science
• Pharmaceutical Science

Background:

• A mathematical model describes drug release from polyvinyl alcohol (PVA) matrices.
• This model characterizes polymer dissolution as chain disentanglement at a threshold concentration.
• Experimental validation is needed to define this characteristic entanglement concentration.

Purpose of the Study:

• To experimentally determine the characteristic entanglement concentration of polymer solutions.
• To relate viscosity changes to molecular chain disentanglement.
• To provide data for refining drug release models from PVA matrices.

Main Methods:

• Viscosity measurements of aqueous polymer solutions across a range of concentrations and shear rates.
• Utilizing a rotational viscometer for data acquisition.
• Fitting flow curves to an asymptotic model to extract viscosity parameters.

Main Results:

• Viscosity parameters were obtained and their relationship with polymer concentration was analyzed.
• A critical concentration was identified, marked by an abrupt change in viscosity properties.
• This critical concentration was directly correlated with molecular chain disentanglement.

Conclusions:

• Viscosity measurements effectively define the characteristic entanglement concentration.
• The identified critical concentration is a key indicator of polymer chain disentanglement.
• Findings support the model of polymer dissolution as a chain disentanglement process in drug release studies.