The Synthesis And Properties Of Temperature-Sensitive Acrylamide Copolymer

The nonionic thermosensitive water-soluble copolymers P (AM-NIPA) of acrylamide (AM) and N-isopropylacrylamide (NIPA) were synthesized by free radical aqueous solution copolymerization, and the ionic copolymer P (AM-NIPA-NaAA) was prepared by incorporating the third monomer sodium crylic acid (NaAA) to the molecule structure of P (AM-NIPA). The copolymer structures were characterized by IR Spectrum and ~1H-NMR Spectrum. The effects of the reaction conditions such as reaction temperature initiator concentration and NIPA monomer concentration on the performance of the copolymer solution were studied; The conversion of copolymerization with the reaction time was measured; the effect factors on thermosensitivity of the copolymer solution were studied; the thermosensitive mechanism of copolymer solution was studied by the fluorescence Spectrum, intrinsic viscosity and DSC; The effects of copolymer concentration, temperature and shear rate on the apparent viscosity of copolymer solution were studied.The result shows that the conditions of copolymer reaction have notable effect on the performance of the product. The apparent viscosity of the copolymer solution declines with the initiator concentration increasing or polymerization reaction temperature rising. When the NIPA monomer amount in the copolymer increases, the apparent viscosity of the copolymer solution decreases.The proportion of monomer and monomer amount in the copolymer has notableeffect on the low critical solution temperature of the copolymer solution. When the hydrophile monomer AM amount increases in the copolymer, the low critical solution temperature of the copolymer solution increases; when the third monomer sodium crylic acid is added to the copolymer of P (AM-NIPA), the low critical solution temperature of the copolymer solution is increased obviously.The chemical structure and concentration of salts have also notable effect on the low critical solution temperature of the copolymer solution. With NaCl CaCl2 and Na2SO4 concentration increasing, the low critical solution temperature of the copolymer solution declines in linearity, which shows that salt has restraining effect on the low critical solution temperature of the copolymer solution. At the same time, Different of salts have different effect intension on the low critical solution temperature of the copolymer solution. When a little Na2SO4 is added to the copolymer solution, the copolymer separates out from solution at normal temperature. When the NaCl and CaCl2 in aqueous solution equaling to Na2SO4 in ion intensity or mol concentration is added to the copolymer aqueous solution, the effect of NaCl and CaCl2 on the low critical solution temperature is less notable than the Na2SO4, and the effect of NaCl on the low critical solution temperature is more notable than the CaCl2, Which indicates that the low critical solution temperature of the copolymer solution is related to the kind of anion or cation of salt.The fluorescence Spectra of P (AM-NIPA) solution indicates that the polarity of media around the pyrene probe keeps unchanged below the low critical solution temperature of copolymer solution, when the temperature of copolymer solution reaches to the low critical solution temperature, the polarity of media around the pyrene probe decreases sharply, which causes the congregating of the hydrophobe structure of the copolymer.The changing rule of intrinsic viscosity of copolymer solution with temperature shows that the intrinsic viscosity of the copolymer in solution declines accordingly with temperature rising, but in the neighborhood of the low critical solution temperature of the copolymer solution, the intrinsic viscosity declines sharply, which indicates that the parameter of mutual effect between molecule of copolymer andwater molecule change abruptly at the low critical solution temperature of the copolymer solution, which results in the change of molecule chain from clew to globe.Copolymer structure has different effects on the apparent viscosity of copolymer solution. Especially, when the third monomer sodium crylic acid is added to the copolymer, the apparent viscosity of copolymer P (AM-NIPA-NaAA) solution is higher than that of the copolymer P (AM-NIPA) at different concentration of copolymer solution. The apparent viscosity of copolymer solution decreases in linearity with the temperature rising, but when the temperature rises to the low critical solution temperature, the apparent viscosity of copolymer solution increases in different degree, which indicates that the copolymer solution exhibits thermothickening effect at special condition. When temperature is above the low critical solution temperature of copolymer solution, the apparent viscosity of copolymer solution decreases sharply. The copolymer solution acts as typical pseudoplastic and thixotropic fluid.