| Polymer surface grafting modification is of prime importance in polymer application,and especially in the biomedical application.This dissertation was design to study visible-light-induced living surface grafting polymerization with the commercial isopropyl thioxanthone (ITX) as the initiator.By studying the grafting mechanism,a new and milder method to modify the surface properties of polyolefines with various monomers was developed.Moreover,the biocompatible property of modification films prepared by visible-light-induced living surface grafting polymerization was investigated.The main results and significance are summarized as follows:1.Polymer substrates with dormant groups on the surface were prepared through the recombination of ITX pinacol radicals and surface radicals generated by the abstract hydrogen reaction.The influence of light intensity,irradiation time,concentration of ITX solution and polymer substrates to the dormant group density was investigated respectively.With the increase of light intensity,the dormant group density increased and reached the maximal value of 0.04μmol/cm2 when the light intensity was up to 10000μW/cm2.Increasing the phtoinitiator concentration and irradiation time also led to higher density of surface dormant group.In a typical experiment,the surface dormant group density reached 6×10-8 mol/cm2 when the concentration of ITX solution and irradiation time was set to 0.5M and 3min respectively.The density of dormant groups attached to LDPE film was higher than that of BOPP film.2.Different polymer layers were prepared on the LDPE films attached with dormant groups by grafting with various monomers,including GMA, St,AA and NVP,under the visible light irradiation.FT-IR measurement proved the formation of PGMA,PS,PAA and PNVP layers on the LDPE film.The surface grafting degree increased linearly with the increase of grafting monomer conversion,which accords to the features of controllable polymerization.The SEM results also indicated that the thickness of grafting layer increased with irradiation time linearly. Based on the experimental results,a mechanism of visible light initiated grafting was discussed.3.To seek for the bioapplication of this visible-light initiated surface grafting method,the HRP encapsulated surface hydrogel was prepared via the grafting polymerization of AM as monomer and PEGDA as crosslinker with HRP as protein model on the dormant groups attached LDPE substrates.The formation of 3-D hydrogel structure was demonstrated by the phase contrast microscope and atomic force spectroscope.Even after 90min irradiation under visible light,the HRP still retained good enzyme activity.4.Positive and negative 3-D micro/nano structure was also prepared via visible light grafting on the surface of dormant groups attached LDPE substrate.The fluorescence labeled antibodies was attached to the functionalized groups on the film surface,which could be observed by fluorescence microscope.5.For the purpose of identifying the mechanism of visible light induced controllable polymerization,the reinitiated capacity of macro-initiater in solution was investigated.The result of photopolymerization showed that the initiating feature of macro-initiater was similar to that on the LDPE surface.The conversion of photopolymerization increased almost linearly with the increase of irradiation time.Although the weight average of resulting polymers increases with the prolonging of irradiation time,the polydisperse index remained between 2.2 to 2.4.
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