Preparation Of Modified PNIPAM Microgels With NHMA And Study On Positive Temperature Response

Temperature-sensitive polymer which is a kind of effective drug carrier can achieve the control release of drugs in the external signal.Among them,poly(N-isopropylacrylamide)(PNIPAM)is a kind of temperature sensitive material which is more common and more widely used,which can be prepared into microgel form and realize the effect of positive temperature response,meaning obvious.PNIPAM microgels were prepareed by emulsion polymerization.The microgel samples were prepared under the conditions of the crosslinking agent dosage of 0.03 g,0.05 g,0.07 g,0.09 g,0.11 g.The relationship between the amount of crosslinking agent and the particle size of PNIPAM microgels was investigated.P(NIPAM-co-NHMA)microgels were prepared by introducing N-methylolacrylamide(NHMA).Two sets of microgel samples were obtained by setting the amount of crosslinking agent in the range of 0.01 g,0.02 g,0.03 g,0.04 g,0.05 g and 0.01 g,0.02 g,0.03 g,0.05 g of surfactant.The relationship between the amount of crosslinking agent and surfactant and the particle size of P(NIPAM-co-NHMA)microgels was investigated.The effects of NHMA on the minimum critical solution temperature(LCST)of copolymer microgels were investigated.The mass ratio of NIPAM: NHMA is 1.5: 0,1.4: 0.1,1.3: 0.2,1.2: 0.3,1.1: 0.4.The results show that the LCST value of the copolymer microgels is between 33 and 40 ? ?.The composition of homopolymerized and copolymerized microgels was determined by FT-IR.The microstructure and particle size of homopolymerized and copolymerized microgels were observed by scanning electron microscopy and transmission electron microscopy.On the basis of homopolymerization and copolymerization of microgels,the effects of crosslinking agent dosage,microgel solution concentration,p H value,Na Cl and surfactant(SDS)on the LCST value of microgels were investigated.The results showed that SDS increased the LCST value of microgels,acid and alkali reduced the LCST value of microgels,the amount of crosslinking agent,the concentration of microgel solution and the Na Cl did not affect the LCST value of microgels.The composite system of loaded microgels was prepared by casting method with rhodamine B as a model drug and two-component polydimethylsiloxane as the film-forming substrate.The release of rhodamine B was observed at 30 and ?45 ?.When the temperature is higher than the LCST value of the microgel particles,the microgel particles will shrink and there will be pores,and the release of rhodamine B through the film increases.This indicate that the film can achieve positive temperature control release,with the increase of the amount of gel particles in the film,and the decrease of the film thickness,the release rate of rhodamine B increased correspondingly.