The Synthesis Of PNIPAM Microgels

The most commonly method for the synthesis of PNIPAM microgels is precipitation polymerization, but the effect of various conditions on the microgels and the formation mechanism was few reported. In this paper, different PNIPAM microgels at different stirring rate, temperature, initiator dosage, crosslinker dosage and monomer concentrations were synthesized. The influence of various conditions in microgels and the formation mechanism of PNIPAM microgels were studied. Based on these studies, the high and low temperature two-stage for the synthesis of PNIPAM microgels were also studied, and the bovine serum albumin (BSA) which contain a double bond was introduced into the PNIPAM microgels. Lay the foundation experiment for introducing the biological molecules (for example: protein, antigen, antibodies, etc.) which do not stability exist at high temperature into the PNIPAM microgels.Stirring rate affects the microgels uniformity under the high temperature. As the stirring rate increased, the uniformity of the microgels was poorer. The better uniformity of the microgels was obtained at 200 r/min. As the reaction temperature increased, the mean diameter of microgels gradually shrinking, but the uniformity of microgels decreased. As the dosage of initiator increased, the mean diameter of microgels first become bigger, and then become smaller. The uniformity of microgels becomes lower with increasing of initiator dosage. As the dosage of crosslinker increased, the mean diameter of microgels becomes smaller and the density of microgels becomes larger. At different monomer concentrations, the microgels from 350 nm to 950 nm were synthesized. As the dosage of monomer concentrations increased, the mean diameter and the density of the microgels gradually become larger. There are two aspects at the formation of microgels. One is the diameter of microgels gradually become larger, another is the density of microgels gradually become larger.Using high and low temperature two-stage method, the microgels from 400 nm to 600 nm at different high temperature reaction time were synthesized. The different BSA dosages which contain a double bond were introduced into the PNIPAM microgels. As the dosage of BSA increased, the mean diameter of microgels becomes larger. The mean diameter of the microgels which synthesized by high temperature and high and low temperature two-stage with temperature changes was studied. The LCST of PNIPAM microgels around 32℃by the visual methods was determined, and the mean diameter of PNIPAM microgels with the temperature rising through the DLS was measured.