Research Of The Fluorinated Temperature-sensitive Microgel Based On N-isopropylacrylamide

Thermo-sensitive hydrogels can respond to the environment temperature, and make irritating response by swelling or shrinking of volume. These materials have been widly concerned and researched, because of their great application potential in drug delivery, tissue engineering, cell culture, biosensors and other biomedical fields. N-isopropylacrylamide (NIPAAm)-based hydrogels was studied concentratively, due to its volume phase transition temperature(VPTT) which is close to the physiological temperature (VPTT≈32℃). In this paper, the classification of thermo-sensitive hydrogels, the modification and application research of NIPAAm-based hydrogels, the preparation and application of fluoropolymer, and other aspects were reviewed systematically.Conventional materials has many defects such as low mechanical strength, low response rate to environment temperature, nonbiodegradability, et al. In this paper, PNIPAAm hydrogel was modified and studied nichetargetingly via copolymerization of NIPAAm and fluorinated acrylate, based on the characteristics of fluoropolymers and the research work in our laboratory on emulsion polymerization.Under the microwave radiation, stable and uniform fluorinated N-isopropylacrylamide thermo-sensitive microgels was successfully synthesized by surfactant-free emulsion polymerization. We chose 2,2,3,4,4,4-Hexafluorobutyl methacrylate(HFMA, FA for short.) and NIPAAm as main monomers, and N,N'-Methylenebisacrylamide(MBA) as cross-linking reagent. The response rate was improved substantially because the microgels were reduced to microns size. Meanwhile, the microgels could be injected and excreted, so we avoided the traditional problem of poor mechanical strength and nonbiodegradability.Through the introduction of hydrophobic fluorine-containing block, we lowered the volume phase transition temperature (VPTT) of the thermo-sensitive hydrogels. This result may help to study the adjusting of thermo-sensitive hydrogels. The homogeneity and stability of the microgel and emulsion were both improved. We also studied the effects of microwave power on the polymerization process and product performance, found that a higher power can help preparing stable microgel and emulsion.A variety of thermo-sensitive microgels with different network structures were prepared by interpenetrating network (IPN), semi interpenetrating network (semi-IPN) and core-shell emulsion polymerization. Effect of different structure on properties of microgels was studied in this article. A comparison of the four sequences (IPN, semi-IPN, hard-shell and hard-core polymer) offers several revelations:there are still some problems to be solved in the fields of IPN and semi-IPN thanks to the thermal shrinkage of polymer network; the emulsion and microgel with hard shell structure were more homogenous and stable than others, but their water imbibitions were poorer; hard-core structure is the best modification method because it not only retains good thermo-sensitivity and hygroscopicity, but also maintains homogeneity and stability of microgel.This thesis makes a preliminary probe into the bonding properties between microgels of fluorinated N-isopropylacrylamide and biomacromolecules for example DNA, protein and so on. The study found that fluorinated N-isopropylacrylamide could be integrated with biological macromolecules without breaking them. The hard-core microgel, in particular, shows an obvious combination with biomacromolecules to protect them. Furthermore, this structure makes the microgel of fluorinated N-isopropylacrylamide monodisperse and stable. It should be pointed out that this kind of thermo-sensitive microgel will have a wide applitcation prospect in the isolation, purification and drug delivery fields.