pH-SENSITIVE POLY (ACRYLAMIDE-co-ACRYLIC ACID) MICROGELS PREPARED BY INVERSE MICROEMULSION POLYMERIZATION

A series of poly(acrylamide-acrylic acid) microgels with different mole percentages of monomers,based on acrylamide (AM), acrylic acid (AA) have been prepared by inverse microemulsion polymerization. Aqueous solutions of AM and AA were used as the dispersed phase for microemulsion with Span80/Tween80/isooctane solution as the dispersion medium, The polymerization was carried out at 30 degrees C in the presence of (NH(4)), S(2)O(8)/NaHSO(3) and N, N'-methylenebisacrylamide (MBA) as the oxidation-reduction initiator and crosslinker, respectively. The presence of characteristic functional groups, pH sensitive behavior, morphology, particle sizes and distribution of microgels have been characterized through Fourier transform infra red spectroscopy (FTIR), turbidimetric method, transmission electron microscopy (TEM) and dynamic light scattering (DLS). FTIR studies confirm the occurrence of AM find AA construction units within the macromolecular chains of microgols, TEM photographs of microgels show that particle number-average diameter of P(AM-co-AA) microgels with the mole percentage of AA 60% in the feed is about 90 nm,so they have large specific surface area. Comparing with PAM micogols,the spherical morphology of P(AM-co-AA) microgels are not very regular due to shrinking during drying operation, Moreover, DLS shows that particle sizes of microgels are increasing and the size distribution of microgels becomes slightly wider with increasing of mole percentage of AA in the feeds. Investigations of turbidimetric method suggest that P(AM-co-AA) microgels are provided with pH-sensitive behavior because of the presence of AA in the feed, and the sensitive pH value is related to the dissociation constant of AA. Due to their interesting properties, P(AM-co-AA) microgels will have a number of potential applications such as drug delivery, adsorption of heavy metal ions and so on.