Study On Photo-Grafted Amine On Film Surface And Its Antibacterial Mechanism And Adhesion Properties

Polyamide-amine dendrimer(PAMAM)has efficient broad-spectrum bactericidal ability,low blood toxicity in organisms,and rarely causes immune reactions.It has become a major research hotspot in the field of biomaterials and is widely used in genes maker modification,drug release,bioadhesive,antibacterial coating,etc.However,the mechanism by which PAMAM kills bacteria remains unclear,and the main controversy has focused on how to determine the site of action between PAMAM and bacteria.In view of the above problems,this paper selected diazirine as the ultraviolet light grafting agent,and used its photoexcitation to stimulate the instantaneous disordered insertion reaction of carbene radicals to CH and other structures,and PAMAM is grafted onto the PET surface in the form of a monolayer.The roughness is controlled within 20 nm to ensure that it can contact the cell wall of Gram-positive bacteria(20-80 nm)without touching the cell membrane,to limit its action site,and test its bactericidal properties.The results show that PAMAM can stimulate the formation of spore-like structure on the surface of S.aureus and dissolve to death without contacting the cell membrane,which provides a powerful experimental proof for the theory of PAMAM induced sterilization.In order to be closer to the use environment,this paper selects PET nuclear pore membrane as the substrate and PET as the semi-crystalline polymer material to ensure the smoothness of the system;carbene free radical grafting does not exist in the traditional chain growth process and can be effectively grafted the branch length is controlled;the molecular structure of PAMAM is highly controllable,with a diameter of about 5 nm.Therefore,in this paper,the monolayer PAMAM grafting and roughness control can be achieved.In addition,the method of grafting bis-aziridine ultraviolet light to prepare a monomolecular layer PAMAM is extended to low surface energy polyethylene to improve the surface polarity of polyethylene and improve the adhesion properties of polyethylene.The main work of this paper is as follows:1.Using diazirine as a UV-excited grafting agent,the PAMAM was bonded was bonded to the PET surface to form a monolayer structure,and the effect of the excitation process on the graft concentration and morphology was also studied.The carbene precursor 4-[3-(trifluoromethyl)-3H-diazirine-3-yl]benzyl bromide is excited by 365nm ultraviolet light to generate carbene radicals,which are inserted into the surface CH bond to form bromine functionalized surface;PAMAM graft layer was formed by substitution reaction of a large number of primary amines with benzyl bromine on PAMAM surface.The monolayer PAMAM structure on the surface of the PET film was qualitatively characterization by contact angle(CA),nano-infrared(Nano-IR),X-ray photoelectron spectroscopy(XPS),atomic force microscopy(AFM),orange yellow Ⅱ dye solution dyeing and other tests of,and the influence of reaction parameters on the graft structure was investigated.The concentration of amine cations introduced into the surface layer was 3.5×10-9 mol/cm2 and 2.9×10-9 mol/cm2,which was calculated by dyeing orange yellow Ⅱ dye solution,and the height of the uniformly grafted dendrimer on the surface was observed by AFM at a height of about 5 nm.This indicates the formation of a monolayer of PAMAM on the surface.This method also provides a new method for the introduction of reactive functional groups on the surface of low surface energy polymers,which has potential application value in the improvement of surface grafting properties and adhesion properties.2.The sterilization effect of the PAMAM on the surface immobilized monolayer without entering the bacterial cell wall was investigated the effect of PAMAM on the sterilization efficiency was stuided,and the moephologic of bacteria during the death process was captured.Using fluorescent dyes for live-dead staining,it was found that PET-DIA4-PAMAM and PET-DIA8-PAMAM can effectively kill bacteria,causing the bacterial cell wall to rupture and release the nuclear structure.The corresponding sterilization rates are about 54%and 78%.The changes in cell morphology during the sterilization process was characterized by SEM,and the results show that PET film after grafting PAMAM has good antibacterial adhesion and the cationic polymer can stimulate bacteria to produce spore structures on the surface without puncturing the wall,and then die.The experimental results provide strong evidence support for the theory of PAMAM end group induced sterilization theory.3.Using the UV grafting reaction of diazirine,polyetheramine T403 was grafted onto the surface of polyethylene(PE)to form an amine group that can undergo curing reaction with the adhesive to enhance the interfacial force and improving the PE Bonding performance.The total reflection infrared spectroscopy(TFIR-ATR)was used to characterize the surface group changes of PE after grafting,and it was found that the-NH2 absorption peak belonging to T403 appeared on the surface of PE,which proved that T403 was successfully grafted onto the surface of PE;the water contact angle experiment proved The polarity and wettability of the PE surface were improved,and the surface energy of the PE before and after grafting was calculated.It was found that the surface energy of the PE increased by 2.2 times after grafting.The tensile shear test was used to characterize the bonding strength between PE and aluminum sheet after grafting.The tensile shear strength can reach 9.9MPa,and the failure type is PE body failure.