Characterization of thermo and pH responsive NIPAM based microgels and their membrane blocking potential

This work aims to study the behavior of temperature-responsive p(NIPAM) and temperature/pH-responsive p(NIPAM)/acrylic acid (AA) microgels. Three microgels were synthesized using surfactant free emulsion polymerization technique, these are p(NIPAM), p(NIPAM)-co-AA 95:5% (w/w) and p(NIPAM)-co-AA 90:10% (w/w). Dynamic light scattering was used to study the behavior of diluted microgel dispersions (0.5%, w/w p(NIPAM)), while rheology was used to study the viscosity of 2% (w/w) p(NIPAM) dispersions. The characterization data indicate the swelling/deswelling and flocculation/deflocculation behavior of the microgels. The conditions required for flocculation were used to test the ability of the microgel dispersions to block a membrane of pore size 5 mu m. In 3 h, p(NIPAM), p(NIPAM) 5% AA (w/w) and p(NIPAM)10% AA (w/w) blocked the membrane (decrease the flow rate) by 96.16, 59.44 and 59.8% respectively. Thus, the controlled flocculation of microgels may be used in applications where pore blocking is important such as the treatment of dentinal hypersensitivity, given that the VPTT of p(NIPAM) is approximate to 34 degrees C, which is very close to the human body temperature. (C) 2013 Elsevier B.V. All rights reserved.