Simulation of bicontinuous phase formation in additive-filled and shape-asymmetric diblock copolymers

添加剂填充和形状不对称二嵌段共聚物中双连续相形成的模拟

• 批准号: 0756248
• 负责人: Fernando Escobedo
• 金额: $ 21.65万
• 依托单位: Cornell University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-05-01 至 2013-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0756248&HistoricalAwards=false
• 关键词: Simulation; bicontinuous; phase; formation; additive

CBET-0756248EscobedoIntellectual MeritThe goal of this project is to use molecular simulation to (1) quantify the impact of polymeric and nanoparticle additives on the onset and structure of bicontinuous phases in linear diblock copolymers (DBC), and (2) elucidate the effect of entropic disparities between blocks of DBC chains on the behavior of bicontinuous phases. The first goal is focused on understanding how additives with selective affinity for a given block will distribute and modify the structure of complex DBC bicontinuous phases (like the gyroid, double diamond, and plumbers nightmare phases where the minority component block forms two interweaving 3D networks); it is envisioned that a suitable choice of additive type, size, affinity, and concentration may suppress or stabilize a particular bicontinuous phase. A specific aim is thus to elucidate the design of optimal additives (e.g., in size and topology) that maximize the composition range of stability of a target bicontinuous phase. The existence of competing co-continuous phases (those whose minority block forms a single 3D network) will also be investigated. Our second goal is to systematically quantify the effect of disparities in block thickness and backbone flexibility on bicontinuous phase behavior. Athermal molecules having intrinsic disparities in thickness (shape) and stiffness can lead to asymmetricalpacking interactions, i.e., an effective "repulsion" between opposite ends of the particles which could give rise to a phase behavior akin to that of conventional DBCs (that have an energetic inter-block disparity). There will be an investigation as to how to design systems where entropy, as opposed to energy, would be the main driving force underlying the assembly of different bicontinuous phases. Starting from the analysis of bicontinuous phases of pure DBCs via both on-lattice Monte Carlo simulations and continuum space Monte Carlo and molecular dynamics simulations, the following tasks are carried out: (i) determining the effect of selective additives (polymers and nanoparticles) of different sizes and structure on such bicontinuous phases, particularly in the particle-concentrated regime, (ii) simulating off-lattice coarse-grained models of DBC-like molecules with varying disparities in block affinity, flexibility, and thickness (pure and with additives) to determine how such changes affect the phase behavior and how they could be exploited to stabilize different bicontinuous phases. To map out reliable phase diagrams and improve ergodic sampling, several Monte Carlo methods are used and further developed; in particular, optimized expandedensemble techniques for measuring free-energies and for chemical potential equilibration.Broader ImpactsThis investigation provides phase diagrams that will serve as "road maps" which could not only be used to correlate simulations with experimental data but also to guide future experimental efforts toward more technologically targeted systems. Given Today's unprecedented ability to synthesize copolymers of precise architecture and composition as well as hybrid organic-inorganic materials and nanoparticles, a better microscopic understanding of the structure and phase behavior of fluids containing these building blocks could provide a sounder basis for rational design of new materials for future applications, including energy-storing devices like fuel cells. The close collaboration of the PI with an experimental group at Cornell provides the synergy between simulation andexperimental efforts and that our findings will also be disseminated within the community ofexperimental polymer-chemists. Dissemination of results to industry is made through Cornell's annual Polymer Outreach Program symposium. The main educational outcome will be the training of a Ph.D. student who will also serve as a link with an experimental group at Cornell. In addition, it is expected that al least one undergraduate researcher from a different university will work on this project during a Summer via the REU program of CCMR (Cornell Center for Materials Research) and another Cornell undergraduate during two regular Semesters. Results of this investigation will be used in at least two classes: a new course on molecular simulations, and the advanced thermodynamics core course.

CBET-0756248EscobedoIntellectual Merit该项目的目标是使用分子模拟来（1）量化聚合物和纳米粒子添加剂对线性二嵌段共聚物（DBC）中双连续相的开始和结构的影响，以及（2）阐明熵的影响DBC 链块之间对双连续相行为的差异。第一个目标重点是了解对给定块具有选择性亲和力的添加剂如何分布和修改复杂 DBC 双连续相的结构（如螺旋体、双金刚石和水管工噩梦相，其中少数组分块形成两个交织的 3D 网络） ;预计添加剂类型、尺寸、亲和力和浓度的合适选择可以抑制或稳定特定的双连续相。因此，一个具体目标是阐明最佳添加剂的设计（例如，尺寸和拓扑结构），以最大化目标双连续相稳定性的组成范围。还将研究竞争共连续相（其少数块形成单个 3D 网络的相）的存在。我们的第二个目标是系统地量化块厚度和主链柔性的差异对双连续相行为的影响。在厚度（形状）和刚度方面具有内在差异的非热分子可能会导致不对称堆积相互作用，即粒子相对端之间的有效“排斥”，这可能会产生类似于传统 DBC（具有能量）的相行为。块间​​差异）。将研究如何设计系统，其中熵（而不是能量）将成为不同双连续相组装的主要驱动力。从通过晶格蒙特卡罗模拟和连续空间蒙特卡罗和分子动力学模拟分析纯 DBC 的双连续相开始，执行以下任务：（i）确定选择性添加剂（聚合物和纳米粒子）的影响这种双连续相上的不同尺寸和结构，特别是在颗粒集中状态下，（ii）模拟具有不同块亲和力差异的类 DBC 分子的离晶格粗粒模型，灵活性和厚度（纯的和含有添加剂的），以确定这些变化如何影响相行为以及如何利用它们来稳定不同的双连续相。为了绘制可靠的相图并改进遍历采样，使用并进一步发展了几种蒙特卡罗方法；特别是，用于测量自由能和化学势平衡的优化扩展系综技术。更广泛的影响这项研究提供了相图，将充当“路线图”，它不仅可以用于将模拟与实验数据相关联，还可以指导未来的实验工作转向更具技术针对性的系统。鉴于当今合成具有精确结构和成分的共聚物以及杂化有机-无机材料和纳米粒子的前所未有的能力，对含有这些构件的流体的结构和相行为的更好的微观理解可以为新材料的合理设计提供更坚实的基础适用于未来的应用，包括燃料电池等储能设备。 PI 与康奈尔大学实验小组的密切合作提供了模拟和实验工作之间的协同作用，我们的研究结果也将在实验高分子化学家社区内传播。通过康奈尔大学的年度聚合物推广计划研讨会向业界传播结果。主要教育成果将是培养博士学位。学生还将担任康奈尔大学实验小组的联络人。此外，预计至少一名来自不同大学的本科生研究人员将在一个夏季通过 CCMR（康奈尔材料研究中心）的 REU 项目和另一名康奈尔大学本科生在两个常规学期期间从事该项目。这项研究的结果将至少用于两个课程：分子模拟新课程和高级热力学核心课程。