嵌段共聚物自组装纳米薄膜.ppt

单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Free-Standing Nanomaterials from Block Copolymer Self-Assembly,llye88,化学,所,Main Reference,Outline,Introduction,Experimental Part,Results and Discussion,Conclusions,Innovations and Problems,References,1.,Introduction,Amphiphilic block copolymers(BCs),could control material interfaces.The 3D construction is directed by the assembly of BCs micelles,prepared in situ,during the,spin-coating,of the block copolymer solution.,BCs in,selective solvent,lead to the preparation of,core-shell micelles,with,a dense insoluble core,and,a diffuse shell,partially swollen by the solvent,a dense insoluble core,内核,micelles,a diffuse corona,核冠,In this work,，,the preparation of stable nanostructure assemblies in,one step,from homogeneous solutions of ABA triblock copolymers.,The success of this strategy,is essentially due to the design of very,stable micelles,prepared and self-assembled in situ in,few seconds,by solvent evaporation,Self-Assembly Nanomaterials,The glassy PSAN blocks,will,enable the formation of compact aggregates,constraining the micelles to be kinetically frozen at room temperature,whereas,the flexible PEO block,will enable,the dynamic transitions between,looped,and,bridged,chain conformations,.,looped,bridged,Photon Cross Correlation Spectroscopy,Photon Cross Correlation Spectroscopy,（,PCCS,），,光子交叉相关光谱法,PCCS,已用于纳米颗粒粒径测量,其技术日益成熟并成为,纳米颗粒粒径测量,的有效方法。其测量原理是建立在颗粒的布朗运动之上。随着颗粒的布朗运动,散射光强围绕某一平均值不断起伏涨落。,PCCS,可以,直接测试高浓度试样而不需要稀释,。测量结果完全真实的反映了被测试样品的实际粒度及分布状态,PCCS,测定的参数为：,平均粒径和多分散指数,吴立敏，王晓艳,.,纳米、亚微米颗粒粒度的测量,光子相关光谱法,上海计量测试,，,2003,年,30,卷,3,期,2.Experimental Part,Sythesis of the Triblock Copolymer,a.Esterification,PEO+Acryloyol Chloride,（,丙烯酰氯,）,PEO-acrylate(I),b.Intermolecular Radical Addition,I+MAMA-SGI alkoxyamine macroalkoxyamine-based PEO(II),c.Preparation of Triblock Copolymer,II+Styrene+Arylonitrile,P(St,317,-co-AN,262,)-b-PEO,795,-b-P(St-co-AN),Preparation of Polymer Films,a.Dissolving the Triblock Copolymer in a DMF/toluene mixture,b.Spin-coating the homogeneous solution onto a Si wafer,evaporate solvent,Synthetic Producure,3.Results and Discussion,Sythesis of the,Triblock Copolymer,Precursor,Preparation of,Particle,Nanomaterial,Preparation of“,Spider Web,”Nanomterial,3.1 Preparation of Particle Nanomaterial,The preparation of superstructure,homogeneous solution,:,PSAN-b-PEO-b-PSAN,selective solution,：,DMF/toluene,(,50/50 v/v,),100 mg/mL,spin-coated on Si wafer,No micelle,could be detected in the solution by,PCCS,even after increasing the concentration up to,200 mg/mL,which seems to indicate,a high CMC in this solvent system,.Beyond this concentration,the polymer solution was,too viscous,to be analyzed.,选择性溶剂,DMF,，,二甲基甲酰胺，极性非质子性溶剂,Toluene,，,甲苯，非极性溶剂,Figure 2(A).Self-standing nanoparticle superlattice film prepared from a DMF/toluene(50/50,v/v)copolymer solution.,AFM top view,of the superstructure and,size distribution,of particle diameter determined by a picture analysis over 100 particles.,Diameter,：,c.a.50nm,Narrow size distribution,AFM image,a,Large-scaled AFM image,of the nanoparticle film,top surface,.,b,c,3D AFM images,showing the,high regularity in roughness,with,Z value(,21.3nm,)close to the Radius(c.a.,25nm),of one polymer particle.,A,dense packing,of nanoparticles,Large-scaled AFM image,Figure 2,(B)SEM,top,bottom,and,cross sectional,view,of a stretched nanoparticle film.,stretching the film can take place without forming cracks.,(C)Crack free stretched nanoparticle film.,(D)Enlargement of the cross-section showing a homogeneous nanoparticle morphology.,SEM image,The,water contact angle,(WCA)of the nanoparticle film was measured to be 35,which confirms the presence of,hydrophilic PEO,on the particle film surface.The,hydrophobic PSAN core,is“shielded”by,the PEO corona,，,so the surface properties of the material is only related to,the thin PEO layer,.,推断,不溶性的,PSAN,嵌段：内核（,micellar core,）,spherical micelle,可溶的的,PEO,嵌段：核冠（,micellar corona,）,A dense packing of nanoparticles,Film,Formation Mechanisim,利用水触角测量仪进行电晕处理聚合物薄膜的试验方法,Formation Mechanisim of,Nanoparticle Film,Figure 3.the self-assembly of PSAN-b-PEOb-PSAN into,nanoparticle film,A,B,A Triblock Copolymer,After the appearance of micelles,the solvent evaporation leads to a progressive,decrease of the micelle-to-micelle distance,.,When micelles are close enough to interact,dynamic association could take place through,bridged conformations,of the ABA polymer chains,，,which leads to permanent nanomaterials.,First solubilized the copolymer in,DMF,(100 mg/mL)followed by a slow addition of,water,.Dialyze remove DMF,In this case,micelles were detected in,PCCS,in high concentration with a hydrodynamic diameter of 110 nm,which confirms the ability of the BC to be assembled into,micellar morphology,.,An alternative strategy,DMF/water,This,alternative strategy,seems to be,less efficient,in terms of,particle organization,.,loose,During the,spincoating,of the,water-based dispersion,micelles come into contact with the surface and stay probably at around this place,without any efficient dynamic adjustment,.,DMF/toluene,DMF/water,Loose nanoparticle film,DMF/water,It must be mentioned that nanoparticle films can also be,observed from BC solutions in,pure DMF,.However,the,reproducibility was poor,.,Small unwanted changes in the process parameters might switch the organization from,nanoparticle,to,short worm-like superstructure,pure DMF,Repeated,experiment,Mixture,:Spherical,Short worm-like film,Spherical micelle film,By adding some,toluene,the window to target,the worm-like structure,is enlarged,and,the,reproducibility,is ensured,.,Disconnected,worm-like micelle film,with diameter of about 50 nm is,observed by AFM when,pure toluene,was used as solvent,AFM top view,before stretching,SEM top and cross-sectional views,after stretching,Figure S5.,Short disconnected worm-like micelles,pure,toluene,disconnected worm-like micelle film,Processing,is the key step and can alter the quality of the material.,Example,Increasing,the speed rate of the spin coater,micelles do not have enough time to self-organize through a dynamic process and so,rough surface,with some,failures,can be observed.,Figure S6.AFM image DMF/toluene(50/50),increasing the speed ramp from 50 to 300 rpm.s,-2,.,3.2 Preparation of“Spider Web”Nanomaterial,As diffusitivity,of block copolymers in solution is,too small to respond,to the fast change of solvent concentration and composition during,the evaporation stage,the equilibrium micelle morphology,is never reached.,In this work,by increasing the,toluene content,from 50 to,75,vol%,a“spider web”superstructure with,a highly connected network of worm-like micelles,is observed instead of a nanoparticle film.,The worm-like micelles,have a diameter of 50 nm and their connections make,pores,with an average size of 90 nm and a,broad,pore size distribution,Figure 5.Self-standing“spider web”superlattice film obtained from a,DMF/toluene (25/75,v/v)copolymer solution.,T,he,top surface,of the,interconnected worm-like micelle network,AFM image,The expected,3D porous network,seems,not to be isotropic,with an organization close to a,multilayer,system with a,preferential,2D construction.,SEM image,Figure 6.SEM,cross-sectional view,of the,“,spider-web,”,nanomaterial.,During the evaporation stage,micelle concentration increases and some interconnections take place between micelles thanks to the,dynamic formation of bridged conformation,of the ABA triblock copolymer.,Y junction,Large-scaled AFM image,Figure 5.(B)the self-assembly of,PSAN-b-PEO-b-PSAN,into a“spider web”,superstructure.,Forming Mechanism,4.Conclusions,This strategy is based on the,dynamic interactions between flower-like micelles,leading to a,transition between“loop”and“bridge”conformations of the ABA chain,.,This bridge conformation enables the formation of,self-standing crack free nanostructured film,（无裂缝）,By playing with the solvent system,spherical or worm-like micelles are formed in situ and assembled into two different nanomaterials,the nanoparticle and the“spider web”films,.,球状胶束,“,纳米粒,”,薄膜,蠕虫状胶束,“,蜘蛛网,”,薄膜,5.Innovations and Problems,创新点,1,、本文设计了一种,ABA,型三嵌段共聚物,，在,选择性溶剂,中巧妙构筑出,两种稳定胶束,，再进行,3D,自组装获得,两种很好的薄膜结构,。这为我们进行,大分子自组装,提供很好的借鉴思路。,2,、运用多种先进的表征手段，如,PCCS,、,AFM,、,Large Scaled AFM,、,SEM,从而得出的结论（如薄膜形成机理等）更加准确、有据。,不足改进,1,、没有说明溶剂中,DMF/toluene,比例,为什么确定为,50/50,、,25/75,，以及其他的比例是否会得到其他的优异结构。,2,、还可进一步探索其他的溶剂。,3,、,力学性能,还需进一步测试,My Reference,1,、,Free-Standing Nanomaterials from Block Copolymer Self-Assembly,Macromolecules,2010,43,5060-5065,2,、朱锦涛等，,两亲性嵌段共聚物在选择性稀溶液中的自组装,J.,2005,年全国高分子学术论文报告会,3,、王国建，多组分聚合物结构与性能（第一版）,M.,北京：化学工业出版社，,2010,年,5,月，,170-191.,4,、袁建军等，嵌段共聚物自组装及其在纳米材料制备中的应用,(,上,)J.,高分子通报,，,2002,年,，第,1,期,5,、袁建军等，嵌段共聚物自组装及其在纳米材料制备中的应用,(,下,)J.,高分子通报,，,2002,年,，第,2,期,Others,PH,核壳冠结构,Thank you!,Any question,