A discontinuous volume collapse occurs on binding of tetraphenylphosph
onium chloride (TPPC) to the anionic polyelectrolyte network poly[2-(a
crylamido)-2-methylpropanesulfonic acid] (PAMPS) gel. The amount of TP
PC inducing volume collapse decreases with increasing temperature. The
TPPC binding to the gel is noncooperative and insensitive to temperat
ure change in spite of the strong hydrophobic interaction of TPPC. The
mechanism of the TPPC binding is discussed.