| In situ nanogel is composed of environmentally sensitive polymers.The structure of nanogels will change when the environmental conditions are changed,such as pH,temperature,ionic strength and light.Thermosensitive in-situ gel has the critical phase transition temperature and can undergo phase transition with the change of ambient temperature.It is the most widely studied and relatively sensitive in situ gel.The gelation process is characterized by viscosity changes in the macro scale,and the microstructure changes in the inner part.Because the gel contains hydrophobic and hydrophilic segment structure,the interaction force between micelles increases with the increase of ambient temperature,resulting in gelation and formation of network structure.Because of its mild behavior,good injectable property,easy administration and good biocompatibility,in situ gel sol-gel transition has shown great potential in biomedical engineering such as tissue engineering scaffolds,drug delivery,three-dimensional cell culture and so on.In this paper,a series of copolymerized nanogels were synthesized by emulsion precipitation copolymerization.The structure and properties of the synthesized nanogels were characterized.The phase transition mechanism and gelation properties of the nanogels were characterized.The main work is as follows:(1)Preparation of thermosensitive nanomaterials and characterization of their gelation propertiesA hydrophobic monomer,cyclohexylacrylamide(CHAA),was synthesized by acyl chlorination and its structure was characterized.A series of P(NIPA-co-CHAA)nanogels were prepared by copolymerization of emulsion and copolymerization of the monomer and thermosensitive monomer N-isopropylacrylamide(NIPA).The structure and morphology were characterized by Fourier transform infrared spectroscopy(FTIR)and transmission electron microscopy(TEM).Dynamic light scattering laser particle sizer(DLS)was used to explore the change trend of particle size dispersion of P(NIPA-co-CHAA)nanogels with different monomer ratios,crosslinking agents content and surfactant content,and the temperature sensitivity of P(NIPA-co-CHAA)nanogels was also discussed.The gelation properties of nanogels were characterized.It was found that PNC2 nanogels could achieve sol-gel transition at 3wt%concentration only.The gelation temperature and time were characterized by rheometer.The sol gel transformation of nanogels could be achieved at gelatinization temperature and the process was reversible.The biocompatibility of P(NIPA-co-CHAA)nanogels was detected by using human embryonic lung fibroblast,and it was found that it had good biocompatibility.(2)Study on phase transition mechanism and characterization of gelation of dual-responsive nanomaterialsA new type of weak acid monomer L-N-propanyl phenylalanine(APhe)was prepared.A series of P(NIPA-co-APhe)copolymer nanomgels were prepared by emulsion copolymerization with NIPA.The good temperature sensitivity and pH sensitivity were characterized by dynamic light scattering laser particle size analyzer(DLS).The mechanism of phase transformation was studied by using variable temperature infrared and variable temperature NMR.It was found that the synergistic effect of benzene ring and carboxyl group in the system could make gelation change and the original structure color could not dehydrate after phase transformation.The gelation properties of the gels were characterized.It was found that the gelatin could be changed rapidly at low concentration(2.8wt%)and the process was reversible.The biocompatibility of P(NIPA-co-APhe)nanogels was detected by human embryonic lung fibroblast,which showed good biocompatibility. |
