Preparation And Application Of Thermal Responsive Hydrogels Based On Four Heavy Hydrogen Bonds(UPy)

Due to its unique properties,namely softness and biocompatibility,hydrogels have great room for development in the fields of biology and medicine now and in the future.The hydrogel is a water-rich soft material formed by crosslinking a hydrophilic polymer or a polymer.In the preparation of hydrogels,most of them rely on dynamic/reversible covalent bonds or non-covalent chemistry,such as hydrophobic association,metal-ligand interaction,dipole-dipole interaction,host-guest interaction,hydrogen bonding,and the like.In this paper,we mainly use hydrogen bonding to design and try to prepare hydrogels.Hydrogen bonding has evolved from the present to the present.Among them,the hydrogen bond system has a single hydrogen bond,a double hydrogen bond,a triple hydrogen bond,a tetrahydrogen bond,and a multiple hydrogen bond.The full name of the four-fold hydrogen bond(UPy)system is 2-ureido-4[1]-pyrimidinone,which can form a strong dimerization index.Hydrogen bonding,and the synthesis process of the four-fold hydrogen(UPy)system unit is simple and the raw materials are cheap and easy to obtain.Therefore,the hydrogen bonding of the tetrahydrogen bond(UPy)system acts as a reversible phase of the hydrogel.Hydrogen bonding acts as a temperature-sensitive force,and it has many applications in materials.Temperature-sensitive hydrogels have broad application prospects in the biomedical field,and have therefore received widespread attention from scholars at home and abroad.There are two sources of hydrogels:natural polymer derivatives and synthetic polymers.Hydrogels prepared from these two materials have their own advantages.For example,natural polymer-derived hydrogels generally have better biocompatibility,degradability,low toxicity,etc.Polymer-based hydrogels generally have better mechanical properties and the like.In this paper,the four-fold hydrogen bond was introduced into the natural polymer gelatin and the synthetic polymer compound as the cross-linking point of the gel,and the effect of temperature and hydrogen bond cross-linking density on the properties of the hydrogel was studied.Specifically divided into the following research content:1.Synthesis of a four-fold hydrogen bond(UPy)system unit:UPy-NCO was prepared by reacting 2-amino-4-hydroxy-6-methylpyrimidine(MIC)with hexamethylene diisocyanate(HDI).The reaction product was characterized by a nuclear magnetic resonance spectrum and a carbon spectrum,and a Fourier infrared spectrometer.2.Research on modification of gelatin(Gelatin)based on natural polymer materials.The grafting reaction of the free-NH2 in the gelatin chain with the isocyanate group(-NCO)in the tetrahydrogen bond monomer(UPy-NCO)introduces a four-fold hydrogen bond system(UPy)to obtain a graft modified gelatin..The degree of grafting was determined by characterization of ninhydrin’chromogenic.The tetrahydrogen bond(UPy)system is grafted onto the side chain and the crosslink density of the gelatin chain is achieved by physical crosslinking.The monomeric content of the four-fold hydrogen(UPy)system was used as a variable to study the glass transition temperature(Tg),contact angle,swellability,structure and properties of hydrogel,and shape memory properties of gelatin.The application of gelatin-based hydrogels was also explored.2-hydroxy-4-amino-5-fluoropyrimidine was used as a model drug to analyze its controlled release effect in gelatin-based hydrogels and the effect of shape recovery on drug release.3.A series of small molecular monomers are used as raw materials to synthesize and prepare polymer hydrogels,and is a physical crosslinked hydrogel with thermal response based on four-fold hydrogen bonding.First,using UPy-NCO,which has been synthesized,to react with 2-hydroxyethyl isocyanate(UPy-HEA);finally UPy-HEA,N,N-dimethylacrylamide(DMA)A shape memory hydrogel having a thermal response was prepared by copolymerization of ammonium persulfate and N,N’-methylenebisacrylamide(MBA).A series of characterizations were performed by nuclear magnetic resonance mass spectrometry,universal tensile machines,and the like.The shape memory properties of the hydrogel and the water content,strength,and porosity of the hydrogel were investigated by changing the hydrogen bond density and temperature of the hydrogel.