Preparation of aqueous latices with N-isopropylacrylamide

The preparation and characterization of monodisperse aqueous latex dispersions prepared from mixtures of N-isopropylacrylamide (NIPAM), acrylamide and N,N′-methylenebisacrylamide are described. Latices were prepared with solid contents up to 2.5%; the maximum acrylamide concentration which gave a good latex was about 1%. Absorbance (i.e. light scattering) of the latices increased when the temperature was raised above the lower critical solution temperature (LCST) of poly(NIPAM). Electron microscopic evidence suggested the latices were swollen to about 1μm in diameter at low temperature but were contracted by about a factor of 10, in volume, when the temperature was raised above the LCST. In 0.1 M CaCl2 the latices had critical coagulation temperatures ranging from 33 to 44°C when the acrylamide charge in the preparation was increased from 0 to 1.24 g l−1.