Abstract:

Polyampholyte microspheres with pH and salt concentration sensitive behaviors were prepared by acrylamide(AM), acryloylxyethyl trimethyl ammonium chloride(DAC) and methacrylic acid(MAA) in ethanol. The shape and conformation of microspheres were determined by transmission electron microscope and infrared spectroscopy, respectively. Meanwhile, the change behavior of the microsphere diameter in various pH solutions and in NaCl and CaCl2 salt solutions was investigated. The results indicated that the diameter of microspheres was 1 177 nm， and polydispersity index(PDI) value was 0.181 at the second step, which were greater than those(d=764 nm； PDI=0.069) at the first step. The diameter of microspheres increased with decreasing pH when the pH was lower than pH=4.3. Whereas when the pH was higher than 4.3, the diameter increased with increasing pH, and a minimum diameter was obtained when the pH was 4.3. At the isoelectric point, the dispersion exhibited a typical antipolyelectrolyte effect in univalent NaCl salt solution. However, in multivalent CaCl2 salt solution, the diameter of microspheres first increased and then decreased.

Key words: pH-responsive, Salt concentration responsive, Polyampholyte, Antipolyelectrolyte effect