THERMOSHRINKING BEHAVIOR OF POLY(VINYLCAPROLACTAM) GELS IN AQUEOUS-SOLUTION

The swelling of newly synthesized slightly crosslinked gels of polyvin ylcaprolactam (PVCa) was studied as a function of temperature. In wate r, PVCa gels undergo a sharp volume transition from a swollen to a col lapsed state on heating. In water/alcohol mixtures, the gel first shri nks and then expands as the temperature is raised. The swelling behavi or of the thermosensitive PVCa gel in surfactant solution depends on k ind and concentration of the surfactant. Normally, an additional swell ing of the gel is observed in the presence of ionic surfactants. Addit ion of the surfactant raises the collapse transition temperature of th e gel. Absorption of the surfactant by the PVCa gel as a function of t emperature and surfactant concentration is analysed in detail.