【作者】 张恒；

【导师】 陈静波； 张彬；

【作者基本信息】 郑州大学 ， 材料科学与工程， 2020， 硕士

【摘要】 嵌段共聚物超薄膜因其可以自组装形成微纳米级结构在微电子器件、传感器以及生物医用材料等领域具有潜在的应用价值,其自组装结构的形态受额外施加的流动场以及其自身结晶行为控制。本文研究了超薄膜体系中的两亲性嵌段共聚物聚苯乙烯-b-聚乙烯基吡啶（PS-b-P2VP）、结晶性嵌段共聚物聚己内酯-b-左旋聚乳酸（PCL-b-PLLA）和聚氧化乙烯-b-聚己内酯-b-左旋聚乳酸（PEO-b-PCL-b-PLLA）自组装的取向和结晶熔融行为,表征了退火时间、去润湿孔接触线宽度以及去润湿孔的生长行为对PS-b-P2VP超薄膜取向图案构筑的影响,探讨并验证了去润湿流动场诱导相分离形成取向纳米结构的机制;同时利用原位加热原子力显微镜（AFM）和广角X射线散射分析技术（WAXS）研究了PCL-b-PLLA和PEO-b-PCL-b-PLLA超薄膜的结晶熔融过程,表征了嵌段共聚物薄膜结晶后自组装结构的形貌以及加热过程中晶体的熔融行为,并根据熔融过程深入了解了具有多结晶性嵌段的嵌段共聚物的自组装过程。主要结果如下:1、利用溶剂蒸汽退火过程中薄膜的去润湿行为可以实现调控PS-b-P2VP超薄膜的自组装结构由各向同性排列到取向排列的转变。研究发现,PS-b-P2VP超薄膜的取向自组装发生在去润湿孔的生长过程中,孔边缘纳米结构的取向度（f_o）随孔的生长时间(t_grow)呈指数增长:f_o～t_grow^1/3。当去润湿孔生长时,相邻孔碰撞可以形成孔接触线,孔接触线内部的P2VP圆柱体展现了更强的平行于孔边缘排列的趋势,退火时间的增加以及孔接触线宽度的减小使自组装结构的取向度增大,最终在孔接触线内可以形成高度有序的取向排列结构。研究认为:PS-b-P2VP超薄膜自组装结构的取向转变是去润湿提供的流动场诱导的,这种平行于孔边缘的排列方式是P2VP圆柱体在流动场的推动下弹性能量最小的最优排列。2、利用配备加热载物台的AFM原位研究了PCL-b-PLLA和PEO-b-PCL-b-PLLA结晶自组装结构的熔融行为,表征了在加热过程中薄膜自组装结构的形貌变化。研究发现:PCL-b-PLLA和PEO-b-PCL-b-PLLA超薄膜结晶后可以形成清晰的多晶片层结构。由于各晶体的熔融温度存在差异,随着温度的升高,PEO晶体首先熔融;达到PCL的熔融温度后,PCL晶体消失,只有PLLA晶体在此温度下存在。根据加热过程中表面形貌以及粘附力的变化,发现在PCL-b-PLLA超薄膜中,PLLA片层和PCL片层交替排列,两个PLLA片层中仅存在一个PCL片层;在PEO-b-PCL-b-PLLA薄膜中,两个PLLA片层之间存在一个或多个PEO片层和PCL片层。研究认为:在结晶过程中PLLA首先结晶,随后PLLA晶体片层可以作为模板限制PCL和PEO在PLLA片层间结晶,从而形成复杂的多晶片层结构。更多还原

【Abstract】 Block copolymer films have potential applications in microelectronic devices,sensors,and biomedical materials because of their self-assemble ability to fabricate micro/nano structures.The morphology of block copolymer films can be controlled by the additional flow field and its own crystallization behavior.In this study,the self-assemble structures of the amphiphilic block copolymer poly（styrene）-b-poly（2-vinyl pyridine）（PS-b-P2VP）,crystalline block copolymers poly（ε-caprolactone）-b-poly（（?）-lactide）（PCL-b-PLLA）and poly（ethylene oxide）-b-poly（ε-caprolactone）-b-poly（（?）-lactide）（PEO-b-PCL-b-PLLA）have been studied.An ordered alignment induced by dewetting was fabricated in PS-b-P2VP films.By analyzing the effect of the annealing time,the width of contact line and the growth behavior of the dewetting holes on the microdomain orientation of PS-b-P2VP film,the formation mechanism of the oriented nanostructures induced by the dewetting flow field was investigated and verified.Furthermore,the melting behavior of self-assembled nanostructures in PCL-b-PLLA and PEO-b-PCL-b-PLLA was investigated by using in-situ hot-stage atomic force microscope and wide-angle X-ray scattering analysis technology.By analyzing the sequential melting process of three block crystals during heating,the formation of self-assembled nanostructures were discussed.The main results are as follows:1.The dewetting behavior of the film can be used to control the orientation of the cylindrical mesophases in PS-b-P2VP films.In the course of dewetting enabled by solvent vapor annealing,cylinders aligned parallel to the dewetting contact line with the size of the ordered domain increasing in the direction normal to the dewetting front.We observed a power law increase of the orientation parameter（f_o） for the P2VP cylinders with increasing time(t_grow)of hole growth:f_o=t_grow^1/3.Arrays of precisely aligned cylinders were achieved in long filaments generated by the coalescence of adjacent dewetting holes.The degree of order of the aligned P2VP cylinders at the contact line was enhanced by increasing the annealing time as well as by decreasing the distance to a neighboring contact line,i.e.,in narrow filaments generated by dewetting.Alignment of cylindrical mesophases was considered to be driven by the dewetting flow field and by minimization of the elastic energy of the P2VP cylinders.2.The melting behavior of self-assembled structure in PCL-b-PLLA and PEO-b-PCL-b-PLLA thin films has been investigated by using in-situ hot stage AFM.PCL-b-PLLA and PEO-b-PCL-b-PLLA thin films have obvious layered nanostructures after crystallization.For the difference of melting temperature for each crystal layer,during the heating process,PEO crystals first melted;the PCL lamellae disappeared at 60°C when PCL crystals melt.At that temperature,the only remaining crystals are formed by the PLLA block.According to the change of the lamellar structure and the adhesion,we found that in the PCL-b-PLLA,the PLLA lamellar layer and the PCL lamellar layer are alternately arranged,and only one PCL lamellar layer exists between two PLLA lamellae.In PEO-b-PCL-b-PLLA,one or more PEO lamellae and PCL lamellae are inserted between PLLA lamellae.It is considered that the isothermal crystallization of the PLLA block is induced first when cooling from the melt.Then,PLLA lamellae form a template,whereupon cooling the other two blocks can crystallize within the PLLA interlamellar spaces.更多还原