【作者】 杨荣巧；

【导师】 史安昌； 李宝会；

【作者基本信息】 南开大学 ， 凝聚态物理， 2012， 博士

【摘要】 嵌段共聚物可以自组装形成丰富的微观有序结构及这些微观结构的潜在应用价值，因此对嵌段共聚物体系的研究一直都是实验和理论上的一个重要课题。对两嵌段共聚物熔体，实验和理论已经证实，随着单体体积分数和单体-单体之间的相互作用强度的变化，该体系可以自组装形成一系列的平衡有序结构，即，层状相、六角排列的柱状相、双连通Gyroid相、体心立方结构的球状相。实践中，人们发现在受限环境下，受限引起体系熵的减小，同时结构受挫程度和表面对嵌段共聚物的作用会强烈的影响其自组装相行为。这些因素诱使了可能具有潜在应用价值的新颖形态的形成，而这些形态在体相下是无法形成的。大量的实验和理论研究表明，随着受限维度从一维（平行板受限）、增加到二维（柱状纳米孔受限），再到三维（球状纳米孔受限），两嵌段共聚物的自组装形态越来越复杂。受限作用对嵌段共聚物微相分离及自组装形态的影响，以及理解这些新奇结构的自组装机理也是聚合物科学研究中的重要内容。添加均聚物到嵌段共聚物体系中也赋予了其新的相行为，如使体系呈现出一些新的有序结构，或使体系呈现宏观相分离。此外，聚合物受限在纳米槽内或接枝在基板上等体系的自组装行为也受到广泛关注。本论文使用模拟退火方法，系统地研究了嵌段共聚物和均聚物共混体系在三维受限环境中、嵌段共聚物受限在圆柱形纳米槽内、以及均聚物接枝在基板上的自组装行为。预测了嵌段共聚物的自组装形态随着均聚物的链长、受限尺度以及聚合物间相互作用强度等因素演化的规律；揭示了受限环境中复杂形态的形成机制；考察了不同参数对方形刷或带状刷自组装形貌的影响。本论文第二章中研究了AB两嵌段共聚物和均聚物A或B组成的共混体系、以及两嵌段共聚物AB和均聚物C组成的共混体系受限在球状纳米孔内的自组装行为。当表面吸引A单体时，发现对称AB两嵌段共聚物和均聚物A共混体系的自组装结构受均聚物含量、均聚物链长和受限尺度影响。随着均聚物含量的变化，体系可形成多种自组装结构，包括类洋葱层、笼状、类拱顶状、螺旋状、堆叠圆盘和圆环、平层、及球状结构。预测了均聚物的链长越短,它们越容易与两嵌段共聚物相容且渗透到后者形成的微相结构的富A畴区内；均聚物的链长越长，它们越难与两嵌段共聚物相容，而导致宏观相分离发生。模拟结果与近期类似体系的相关文献的实验结果有着较好的吻合。当是中性表面时，我们的模拟结果表明：均聚物链长和均聚物含量对两嵌段共聚物的自组装形态的影响与球表面吸引A单体情况相似。当均聚物C亲A单体和而排斥B单体时，对称AB两嵌段共聚物和均聚物C共混体系受限在表面吸引A和C单体而排斥B单体的球内的自组装结构，受均聚物含量、均聚物链长、受限尺度以及A-C间吸引相互作用强度的影响。随着均聚物含量的变化，体系可形成多种自组装结构，包括类洋葱层、笼状、螺旋状、堆叠圆盘和圆环、及球状结构。当A-C单体间吸引相互作用强度较弱时，均聚物越短，共混体系的相容性就越好；且随着均聚物链长的增加，相应的结构出现在较高均聚物含量值。当A-C单体间吸引相互作用强度较强时，均聚物链长对相容性的影响消失。此外，当均聚物C和A、B单体均排斥时，我们考察了球表面对A，B，C嵌段具有不同选择性时，共混体系的四种典型相行为。通过控制均聚物的体积分数，系统的受限尺度，及共聚物的嵌段比例，可以得到具有不同内部图像的聚合物粒子。由于在每个聚合物粒子中均聚物可以分离形成一部分或有些情况下分离形成两部分，因此，均聚物可看作是一个附加控制参数，这个参数控制着共聚物-畴区的形状及对称性。此外，还预测了大量新奇的受限引导的嵌段共聚物形成的自组装结构，其中包括由两嵌段共聚物作为壳层包围着一个均聚物核或一个共聚物和均聚物合并核所组成的壳-核球形纳米粒子，以及由占据球表面不同位置的共聚物和均聚物所构成的双面球粒子。本论文第三章中采用三维粗粒化晶格气体模型和蒙特卡洛模拟退火方法，系统地研究了非对称两嵌段共聚物A9B3以及近对称两嵌段共聚物A7B5受限在圆柱形纳米槽内的自组装行为,并考察了不同参数包括聚合物初始密度、聚合物含量、蒸发速率、聚合物运动次数和初始退火温度等对两嵌段共聚物自组装形态的影响。发现聚合物运动次数和聚合物含量对两嵌段共聚物A9B3的自组装形态影响甚微。嵌段共聚物A7B5在圆柱形纳米槽内自组装形成的薄片穿孔层结构受槽的高度和受限尺度的影响。本章中我们模拟得到的自组装形态和相关文献的实验结果相吻合。本论文第四章中研究了均聚物方形刷和带状刷的自组装相行为，考察了影响方形刷和带状刷自组装形貌的因素。系统地研究了均聚物的链长、接枝宽度、接枝密度、聚合物和基板间相互作用以及聚合物和空气间相互作用等参数对方形刷自组装形貌的影响，以及随着接枝间距增加这些参数对带状刷自组装形貌的影响。方形刷自组装形貌的铺展宽度与接枝宽度的比值D/d和形貌的高度H随着接枝宽度d的变化趋势，及带状刷自组装形貌的高度和振幅随着接枝间距的变化趋势的一部分模拟结果与相关文献的实验结果做了定性的比较。更多还原

【Abstract】 Block copolymers system has been studies as an important issue experimentallyand theoretically, due to their ability to self-assemble into rich nanostructures andtheir potential applications. For the simplest diblock copolymers melts, their phasebehavior is controlled by the volume fraction of one blocks and the strength of theinteraction between the different monomers. A variety of ordered bulk phases,including lamellae, hexagonally packed cylinders, a bicontinuous gyroid structure,and a body centeredcubic array of spheres, have been observed experimentally andtheoretically. In practice, confinements induced entropy decreases, the structurefrustration and the interactions between the block copolymers and surface willstrongly affect the phase behavior of block copolymers. All these parameters cangenerate novel microstructures that may have potential novel applications and can notbe found in bulk phases. A larger number of experimental and theoretical studies haveshown that, with the increase of confinement dimensions from one-dimensionalparallel plate, to two-dimensional cylindrical nanopores, then to three-dimensionalspherical nanopores, the phase behaviors of the diblock copolymers become more andmore complex. Both the influence of confinement on the microphase separation andthe self-assembly morphologies, and the understanding of self-assembly mechanismof these novel structures are important parts of polymer science. Besides putting thecopolymers in the confinement environment, it is known the addition ofhomopolymers to block copolymer melts, blends of block copolymers andhomopolymers also exhibit complex phase behavior, including blends exhibit anumber of new ordered structure, or blends form macroscopic phase separation. Inaddition, much attention has been foucused on the self-assembly of block copolymersplaced into a nano-trough or polymers grafted on a substrate with different lateralspacings.In this thesis, we systematically investigated the self-assembly of diblockcopolymers/homopolymers blends confined in3D spherical nanopores, diblockcopolymers confined in cylindrical nano-trough, and homopolymers grafted on the substrate using simulated annealing technique. The evolutions of self-assembledstructures are predicted with the variation of various parameters, including the chainlength of the homopolymer, the degree of confinement and the interaction of differentmonomers. The self-assembly mechanisms of complex morphologies in confinedenvironment are revealed. The effects of different parameters on self-assembledmorphologies of square and linear array homopolymer brushes are investigated.In chapter two, we investigated the self-assembly phase behavior of symmetricAB diblock copolymer and homopolymer A or B blends, and AB diblock copolymerand homopolymer C confined in spherical nanopores.When the pore surface isattractive to the A-monomers, it is found that the self-assembly of AB/A blendsdepends on the content of the homopolymer, the chain length of the homopolymer,and the degree of confinement. With the variation of the content of homopolymer, theblends exhibit a variety of morphologies and morphological transitions. The observedmorphologies include onion-like structures (with both concentric lamellae andnonconcentric lamellae), cage-like structures, deformed dome-like structures, helicesor stacked toroids, a disk-like layer and spherical structures. The shorter thehomopolymers chain length is, the more likely that homopolymers are compatiblewith the diblock copolymers, penetrating into the A-rich domain region of themicro-structure formed by the latter. The longer the homopolymer chain length is, theharder for the homopolymers to be compatible with the diblock copolymer, which ledto the occurrence of macroscopic phase separation. The simulation results areconsistent with relative experimental results of similar system. When the pore surfaceis neutral to be both blocks, our simulation results show that the chain length andcontent of the homopolymer have similar influence on the diblock copolymers withthe results when the pore surface attracts A-monomers. When the homopolymers Cattractive A-monomers but repulsive B-monomers, it is found that the self-assemblyof the symmetric diblock compolymers AB/homopolymers C blends depends on thecontent of the homopolymer, the chain length of the homopolymer, the degree ofconfinement and the attractive interaction strength between A-C monomers when thepore surface attractive A and C-monomers and repulsive B-monomers. With thevariation of the content of homopolymer, the blends exhibit a variety of morphologies and morphological transitions. The observed morphologies include onion-likestructures (with both concentric lamellae and nonconcentric lamellae), cage-likestructures, helices or stacked toroids and spherical structures. When the A-C attractiveinteraction strength is relatively weak, the shorter the chain length of homopolymer,the better the compatibility of the blend, and the corresponding structures occur at aslightly smaller value for the homopolymer content. When the attractive interactionstrength between the A-C monomers is strong enough, the effects caused byhomopolymer chain length become less pronounced and eventually disappear. In thiscase, the blend has a good compatibility. Moreover, when the homopolymers Crepulsive A and B-momomers, the self-assembly phase behavior of binary blends ofa diblock copolymer (AB) and an incompatible homopolymer (C) is examined forfour typical cases, representing the different selectivity of the pore surface to the A, Band C species. The internal morphology of the spherical polymeric particles iscontrolled by the homopolymer volume fraction, the degree of confinement, and thecomposition of the copolymer. Inside each particle, the homopolymers segregate toform one or, under some conditions, two domains, thus the homopolymers may act asan additional controlling parameter of the shape and symmetry of thecopolymer-domain. A rich array of confinement-induced novel diblock copolymermorphologies is predicted. In particular, core-shell particles with the copolymers asthe shell wrapping around a homopolymer-core or a copolymer-homopolymercombined core, and Janus-like particles with the copolymers and the homopolymerson different sides are obtained.In chapter three, by using coarse-grained lattice gas model and simulatedannealing technique, we systematically investigated the self-assembly phase behaviorof asymmetric diblock copolymer A9B3and nearly symmetric diblock copolymerA7B5confined in cylinderial nano-trough. The model parameters including initialpolymer density, polymer content ratio, evaporation rate, the movement rate ofpolymer, width of mesas and annealing temperature have effect on the self-assemblybehavior of diblock copolymer. The width of mesas, the movement rate of polymerand polymer content ratio have a little effect on the self-assembly morphologies ofdiblock copolymer A9B3. Moreover, we found novel porous slice structures formed by A7B5confined in cylinder nano-trough are affects by different model parametersincluding the height of the trough and degree of confinement. All our simulationresults in this chapter are consistent with related literature experimental results.In chapter four, we systematically investigated the square or linear arrayhomopolymer brush by using a simulated annealing technique. We also studied theself-assembly morphologes of homopolymer brush are effected by any parameter. Theeffection of these parameters including the chain length of homopolymer, graftingdensity, grafting width, the interaction between homopolymer and substrate, theinteraction between homopoymer and air on the self-assembly morphologes ofhomopolymer brush are investigated. Some of our simulation results such as: thetrends of the ratio (D/d) of lateral width (D) to grafting width (d) and the height ofsquare array homopolymer brush change with the d; the trends of morphlogies heightand amplitude of the linear array homopolymer brush change with the line-to-linespacing, are qualitativly compared with relative literature experimental results.更多还原