Preparation And Application Of Polymer Brush By Surface Photo Initiated Polymerization

The surface and interface of materials is the key factor in dictating their properties.As one of the most important methods for the surface modification,polymer brush exhibits a huge potential in application as its simple preparation,structural controllable and so on.Among them,the responsive polymer brush can change its conformation according to the change of enviroment,resulting in different surface properties.Based on this characteristic,it shows broad application prospects in the field of surface antifouling,drug release and biomedicine,etc.At present,the most commonly method for preparation of polymer brush are surface initiated transfer radical polymerization(SI-ATRP),surface light transfer transfer termination(SI-PIMP),nitrogen free radical(NMP),etc.SI-PIMP was used to prepare salt responsive polymer brush system(our previous used SI-ATRP),and investigate the effect of preparation conditions(solvent,reaction time)on properties of polymer brush(surface morphology,wettability,surface lubrication ect).Besides,the combination of SI-ATRP and SI-PIMP were used to prepare mixed brush system with anti-fouling and anti-bacteria,and its construction and the regulation of structure were studied.In this paper,a kind of zwitterionic monomer named N-(4-vinyl benzyl)-N,N'-di alkyl amino(SVBA)with a strong ‘anti polyelectrolyte effect' was synthesised and the factor(solution type,solution concentration,reaction time)which influence its polymerization(thickness,morphology)was explored.The study found that the zwitterionic monomer can be initiated in Na Br solution and Na Cl solution and the kind of salt solution and its concentration have influence on growth rate and morphology of the brush.For salt solution,the growth rate of polymer brushes in Na Br solution is faster than that of Na Cl solution,but the surface roughness in Na Br solution is higher than that of Na Cl solution.For concentration,the growth rate in0.53 mol/L Na Br is max,while in Na Cl solution,the growth rate increased with the increasing of salt concentration and the increase rate is not obvious when the concentration more than 0.53 mol/L.Based on the above results,0.53 mol/L Na Cl were choosen as the reaction solvent to prepare poly SVBA brush.Ellipsometry spectroscopic,atomic force microscopy and automatic optical contact angle were using to character its thickness,surface morphology and contact angle.The friction coefficient of poly SVBA brush in water and 1.0 mol/L Na Cl were determined by friction test and the results were as follows: the friction coefficient in water is much higher than in 1.0 mol/L Na Cl and it can realize the lubrication switch as the solvent enviroment change.The experimental results show that zwitterionic polymer brush with high density and smooth surface can prepare by SI-PIMP.Comparied with SI-ATRP,SI-PIMP has the advantage of fast polymerization and no metal salt catalyst.As the characteristics and advantage of SI-PIMP,the combination of SI-ATRP and SI-PIMP were used to prepare multifunctional surface modified with mixed polymer brush.In this section,poly HEAA and poly METAC were used to construct the “anti-kill” surface.The ATRP initiator and photoinitiator were grafted onto the silicon wafer and a mixed polymer brush modified surface was get by the polymerization of SI-ATRP and SI-PIMP in turn.The composition and thickness of mixed polymer brush are controlled by changing the proportion of initiator and reaction time.Ellipsometry spectroscopic,atomic force microscopy,X-ray electron spectrometer,surface potential analyzer were used to determine its composition,thickness,morphology and zeta potential.The anti adhesion and bactericidal properties of the mixed polymer brush against E.Coli and S.aureus were investigated.The experiments show: 1)The density of polymer brush was controlled by adjusting the mole ratio of the initiators;2)The mixed Poly(SVBA-METAC)brush,prepared by the combination of atom transfer radical polymerization and photo initiate polymerization,having the function of anti-fouling and anti-bacteria at the same time.And its anti-fouling ability increase as the initiator content of atom transfer radical polymerization increasing,while the antibacteria ability increase as the initiator content of photo initiate polymerization increasing;3)When the initiator ratio=5:5,the surface modified with mixed polymer brush showed excellent anti-fouling property and long-term anti-bacteria performance;4)Keeping the initiator ratio=5:5,by changing the reaction time of atom transfer radical polymerization to control the thickness of Poly HEAA,we can find that its anti-fouling performance showed excellent under 40 nm;5)Keeping the initiator ratio=5:5,by changing the light triggertime to adjust the thickness of Poly METAC,we can find that light reaction is efficient and the ideal time of high antibacteria surface preparation can only be 5 min.This study found that,compared with atom transfer radical polymerization,photo initiate polymerization shows more convenient and efficient in preparing polymer brush.And the performance of polymer brush prepared by photo initiate polymerization has no difference with atom transfer radical polymerization.So photo initiate polymerization can be used to prepare polymer brush,especially in preparing mixed polymer brush.