Probing the Effect of
Drug Loading and Humidity on
the Mechanical Properties of Solid Dispersions with Nanoindentation:
Antiplasticization of a Polymer by a Drug Molecule
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Abstract
Amorphous solid dispersions of clotrimazole in the polymer
Kollidon
VA64 were prepared as films in concentrations from 0% to 100% in 10%
by weight increments. Nanoindentation was performed on each film at
18% and 49% relative humidity to assess the effect of drug loading
and humidity on the mechanical properties of the solid dispersions.
Although the addition of clotrimazole to the polymer reduces the glass
transition temperature of the system as measured by differential scanning
calorimetry, the hardness, reduced elastic modulus, and storage modulus
were found to increase to values greater than those of either pure
component up to drug loadings of approximately 60% by weight. Further
addition of clotrimazole to the system resulted in decreased hardness
and moduli with increased drug load. Dynamic vapor sorption of the
dispersions shows that the hygroscopicity of the system is reduced
as clotrimazole is added to the polymer