Preparation and characterization of novel temperature and pH sensitive (NIPAM-co-MAA) polymer microgels and their volume phase change with various salts

Abstract

Novel microgels of iV-isopropylacrylamide (NIPAM)-co-methacrylic acid (MAA) (NIPAM-co-MAA) with different contents of /V.A'-methylene bis acrylamide (MBA) were prepared by emulsion polymerization technique and were studied by Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS) and zeta potential measurement. Effect of pH, temperature and different salts concentration on the microgel particles was investigated. DLS results have shown that the hydrodynamic radius of the microgel increased upon increasing pH and decreased upon increasing temperature. The swelling/deswelling behaviors as determined by DLS showed the ionic repulsions of the car-boxyl group of the methacrylic acid and hydrophobic interaction of NIPAM. The effect of various salts on volume phase transition temperature (VPTT) was also investigated. Upon increasing salt concentration, VPTT became broad and shifted to a lower temperature. Electrophoretic mobility measurements showed an increase with increasing pH and temperature at a constant ionic strength.Grant: Acknowledgement: One of us (AK) acknowledges the financial support of Higher Education Commission, Islamabad, Pakistan under the IPFP program.