Theoretical study of block copolymer self-assembly

聚合物是长的链状分子，可以自然产生(例如DNA)，也可以通过合成技术在实验室生产(例如聚苯乙烯)。我们日常生活中的橡胶和塑料都是由聚合物制成的。嵌段共聚物是通过特殊的合成技术生产的，该技术将一种聚合物物种的末端或嵌段(例如聚苯乙烯)与另一种聚合物物种(例如聚异戊二烯)化学结合。如果不是因为不同区块之间的化学键，不同区块相互排斥的趋势将导致系统分裂成每个物种的宏观区域。嵌段共聚物所能做的最好的事情是按照聚合物的大小，即几十纳米的尺度，将其嵌段分离成结构域结构。自发组织(自组装)成这些微结构的能力使这些材料在需要这种分辨率的应用中潜在地有用。例如，全世界正在进行一项正在进行的努力，以研究嵌段共聚物作为光刻结构模板的使用，以及用于生产金属纳米点和纳米线的有序阵列。这些模板有望将微电子电路缩小到10纳米级，低于传统光刻技术所能达到的水平。我研究的一个方面是了解将嵌段共聚物限制在圆柱形纳米孔中是如何影响自组装过程和创建新的微结构的。这可能会带来潜在的新应用。在处理这些材料时，对系统形成这些结构所需的时间有一个基本的了解也很重要，也就是自组装的动力学。这是我的团队的另一个研究重点。关键问题是：微观结构和动力学之间的关系是什么？形成一个特定结构的动力路径和障碍是什么？我们如何制定一个非平衡理论来回答这些问题？我的团队使用复杂的分析方法和高性能计算的组合来解决这些问题。这项工作预计将在我们对嵌段共聚物动力学的理解方面取得重大进展，并将加强加拿大在新型软材料方面的整体研究努力。

Polymers are long, chain-like molecules that can occur naturally (e.g., DNA) or can be produced in the lab via synthetic techniques (e.g., polystyrene). The rubber and plastics in our everyday lives are made of polymers. Block copolymers are produced by specialized synthetic techniques that chemically bond the end of one polymer species, or block (e.g., polystyrene) to a different polymer species (e.g., polyisoprene). The tendency for unlike blocks to repel would lead the system to separate into macroscopic domains of each species, if it weren't for the chemical bond between the blocks. The best the block copolymer can do is to separate its blocks into domain structures on a scale set by the size of the polymer, that is, tens of nanometers. The ability to spontaneously organize (self-assemble) into these microstructures make these materials potentially useful in applications requiring such resolution. For example, there is an ongoing, world-wide effort to investigate the use of block copolymers as structural templates for lithography, and for the production of ordered arrays of metallic nano-dots and nano-wires. These templates hold the promise of shrinking microelectronic circuits to the 10 nm scale, below that accessible to traditional photolithography. One aspect of my research centres on understanding how confinement of a block copolymer into a cylindrical nanopore influences the self-assembly process and creates new microstructures. This may lead to potentially novel applications. When processing these materials it is also important to have a fundamental understanding of the time it takes the system to form these structures, that is, the kinetics of self-assembly. This is another research focus of my group. Key questions are: What is the relation between microstructure and dynamics? What are the kinetic pathways for, and barriers to, the formation of a given structure? How do we formulate a non-equilibrium theory to answer these questions? My group tackles these problems using a combination of sophisticated analytical methods and high-performance computing. This work is expected to result in major advances in our understanding of the dynamics of block copolymers, and will enhance Canada's overall research effort in novel, soft-materials.