【作者】 王帅；

【导师】 董学会；

【作者基本信息】 华南理工大学 ， 化学， 2024， 博士

【摘要】 分子构造是影响嵌段共聚物本体自组装行为的重要因素,为微观结构的调控提供了广阔的空间。然而,聚合物体系所固有的多分散性严重制约了人们对自组装过程的深入理解。具有精确化学结构和均一链长的离散型嵌段共聚物是探究复杂分子构造对嵌段共聚物相行为影响的理想平台。本论文模块化精准构建了具有不同分子构造的离散型ABC三嵌段共聚物,系统研究了分子构造与自组装行为之间的关系。主要研究内容分为以下四个部分:(一)设计并合成了基于苹果酸衍生物的正交保护单体库,模块化构建了具有均一链长和单体/嵌段序列可控的离散型嵌段共聚物,包括两嵌段共聚物、三嵌段共聚物和交替共聚物等。我们初步探究了两嵌段共聚物的本体自组装行为,不同的相行为揭示了不同嵌段间分离强度的差异。本章工作扩大了可应用于迭代增长的单体多样性,有望为精确大分子的构建提供高效的合成平台。(二)设计并合成了离散型刷-线-刷状和线-刷-刷状ABC三嵌段共聚物,保持分子量和组成不变,探究不同的嵌段构象对相行为的影响。分子的几何形状特征影响局部区域的构象不对称和链段堆积,从而形成不同的分子排列方式。其中,相比于刷-线-刷状分子,线-刷-刷状分子各嵌段间的构象不对称有助于形成高曲率界面的相结构。本章工作揭示了组装体系中构象不对称的重要作用,对于组装结构的调控具有指导意义。(三)设计并合成了离散型星形ABC三嵌段共聚物,探究分子构造对自组装的影响。相比线形分子,星形分子的嵌段连接于同一点,界面附近区域存在严重的空间位阻效应,导致组装过程的构象熵损失更大,结构更不稳定。星形分子几何形状特征更有利于形成具有较高曲率界面的相结构,导致相边界发生偏移。本章工作通过对比,揭示了星形与线形嵌段共聚物不同的分子堆积方式。(四)以纳米粒子POSS模块化合成了离散型ABC三嵌段巨型分子,探究了序列和区域构型对自组装行为的影响。由于存在立体位阻,对位和间位区域异构体的相结构稳定性低于邻位区域异构体。而当序列发生变化时,分子堆积方式存在显著差异。本章工作强调了分子几何形状在自组装中的重要作用,揭示了局部特征对纳米结构形成和演化的重要贡献。本论文通过精确调控分子构造,排除多分散性的干扰,高精度解析了分子构造在ABC三嵌段共聚物自组装所起到的关键作用。本研究工作证明了分子结构的微小差异会对自组装行为产生显著的影响,是调节结构与性能的有效参数。更多还原

【Abstract】 Molecular architecture is an important factor influencing the bulk self-assembly of block copolymers,providing a wide scope for microstructural modulation.However,the inherent polydispersity of polymer significantly restricts the in-depth understanding of the self-assembly process.Discrete block copolymers with precise chemical structures and homogeneous chain lengths are ideal platforms for exploring the effects of complex molecular architecture on the phase behaviors of block copolymers.In this thesis,discrete ABC triblock copolymers with different molecular architecture were constructed modularly and precisely,and the relationship between molecular architecture and self-assembly behaviors was systematically investigated.The main research is divided into the following four parts:(i)A library of orthogonal protected monomers based on malic acid derivatives was designed and synthesized,and discrete block copolymers with uniform chain length and a programmable monomer/block sequence were efficiently synthesized,including diblock copolymers,triblock copolymers,and alternating copolymers.We initially explored the selfassembly behavior of diblock copolymers,and different phase behaviors revealed differences in the strength of segregation between different blocks.This work expands the diversity of monomers that can be applied for iterative exponential growth and is expected to provide an efficient synthetic platform for the construction of precise macromolecules.(ii)Discrete brush-line-brush-like and line-brush-brush-like ABC triblock copolymers were designed and synthesized,keeping the molecular weight and composition unchanged,to investigate the effect of different molecular architecture on the phase behavior.The geometrical features of the molecules affect the conformational asymmetry and chain segment packing in the local region,leading to the formation of different molecular arrangements.The conformational asymmetry between the blocks of the line-brush-brush-like molecular architecture tends to form curved interfaces in the same direction,which contributes to the formation of phase structures with high curvature interfaces.This work reveals the important role of conformational asymmetry in self-assembly,which is instructive for the regulation of phase structures.(iii)Discrete star-shaped ABC triblock copolymers were designed and synthesized to investigate the effect of molecular architecture on self-assembly.Compared with linear molecules,the geometrical features of the star-shaped molecular architecture lead severe spatial potential resistance effect in the region near the interface,greater loss of conformational entropy during the assembly process,and lower stability of the phase structure.The geometrical features of star-shaped molecules are more favorable for the formation of phase structures with higher curvature interfaces,leading to the shift of phase boundaries.The work reveals the different molecular packing of star and linear block copolymers by comparison.(iv)Discrete ABC triblock giant molecules were modularly synthesized with nanoparticle POSS to explore the effect of sequence and regional configuration on the self-assembly.The phase structure stability of the para-and meta-regional isomers is lower than ortho-isomers due to the steric hindrance of unfavorable molecular geometries.Sequence changes produce different molecular packing patterns.This work highlights the important role of molecular geometry in self-assembly,revealing the significant contribution of local features to the formation and evolution of nanostructures.In this thesis,the key role played by molecular architecture in the self-assembly of ABC triblock copolymers is resolved with high accuracy by precisely modulating the molecular structure and excluding the interference of polydispersity.This research work demonstrates that small differences in molecular structure can significantly affect the self-assembly behavior and is an effective parameter to regulate the structure and properties.更多还原