7: POLY(ARYLENE ETHER SULFONE)S 197
immiscible due to the hydrophobic and hydrophilic
nature of the polymers. However, the blends are com-
patible over the entire range of compositions. They
exhibit a highly organized arrangement of both the
phases. The PVP is dispersed uniformly in the contin-
uum of the PES even when it is the major component.
The performance with respect to controlled drug
release has been tested with acetaminophen. After an
initial burst, which takes place in the first 30 min, the
drug release drops and becomes steady for the rest of
the time. The i nitial burst effect is attributed to the
greater concentration drop across the membrane at the
start of the process.
7.4.2.3 Nucleotide Mimetics
Poly(ether thioether)s, poly(ether sulfoxide)s, ...