Brush Particle-Based Building Blocks for High Refractive Index Composites

非技术摘要发光、吸收或弯曲光线的光学设备需要机械保护，因为划痕或裂缝可能会导致不需要的光散射。这种涂层必须具有一系列不同的性能，包括机械弹性和高折射率；前者是保护底层设备所必需的，而后者确保最大的光学性能，因为通过保护层，光被弯曲到设备。但是，大多数材质只能针对这些目标条件之一进行优化。在材料研究部固态和材料化学项目的支持下，罗布·麦克法兰教授和他的研究小组开发了新的策略来合成由机械坚固的聚合物基质中嵌入的高折射率纳米颗粒组成的复合材料。这些材料可以很容易地在低温下形成合适的宏观形状，然后通过热交联形成机械稳定的固体。研究人员研究了如何以及为什么使用这种合成方法可以在基质中加入更大比例的高折射率成分，从而产生具有理想机械和光学性能的材料。这些材料的简单合成方法可能会在未来制造更复杂的器件，这些器件可以用来定制材料反射，以诱导结构着色或抗反射性能。这种材料具有粘合剂、涂层和传感器等优点，可以耦合到光学设备上。此外，该项目为来自代表性不足群体的社区大学生提供了参与STEM研究的机会，使他们能够获得当前化学研究技术的经验和对潜在职业机会的洞察。该项目能够提供真实的实践体验，帮助这些学生寻求高等教育机会或STEM职业生涯。技术概述在材料研究部固态和材料化学计划的支持下，利用含有大量高折射率纳米颗粒的可交联性聚合物接枝纳米颗粒(PGNPs)来合成聚合物/纳米颗粒复合材料。对这些材料的基本结构-性能关系进行了系统的研究，以解释这些材料的光学和力学性能如何受到大量填料含量的影响。由于无机含量的控制，目标材料具有可调的折射率(高达85wt.%)，但也具有优于单独的裸聚合物的机械性能。具体地说，研究人员研究了以下几个方面：i)开发材料-通用的方案来合成和交联具有不同无机纳米颗粒和聚合物组成的PGNPs，ii)充分表征所得到的结构的机械和光学性质，以及iii)开发通过有序的纳米颗粒组织或不同复合组成的多层堆栈来诱导光子带隙结构的方法。进行的基础合成科学和材料表征工作使一类新的光学材料成为可能，并为将聚合物刷接枝到无机颗粒和在纳米级表面诱导共价键的形成提供了更好的设计参数。这项工作既推进了固态材料开发的基础化学，又为光学设备提供了高度有用的复合材料。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Non-Technical SummaryOptical devices that emit, absorb, or bend light require mechanical protection, as scratches or cracks can cause undesirable light scattering. Such coatings must have a range of different properties, including both mechanical resilience and high refractive indices; the former is necessary to protect the underlying device, while the latter ensures maximum optical performance, because through the protection layer the light gets bent towards the device. However, most materials can only be optimized for one of these target criteria. With this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, Prof. Rob Macfarlane and his research group develop new strategies to synthesize composite materials consisting of high refractive index nanoparticles embedded within a mechanically robust polymer matrix. These materials can be easily formed into appropriate macroscopic shapes at low temperatures, then thermally crosslinked into mechanically stable solids. The researchers study how and why significantly larger fractions of the high refractive index components can be incorporated in the matrix with this synthesis method, which then results in materials that have ideal mechanical and optical performance. The simple synthesis methods for these materials potentially allow for the fabrication of more complex devices in the future that can be used to tailor material reflection to either induce structural coloration or anti-reflective properties. Such materials have benefit as adhesives, coatings, and sensors coupled to optical devices. In addition, the project provides opportunities for community college students from underrepresented groups to participate in STEM research, allowing them to gain both experience in current chemistry research techniques and insights into potential career opportunities. This program enables real-world, hands-on experiences to aid these students in pursuing higher education opportunities or STEM careers. Technical SummaryWith this project, supported by the Solid State and Materials Chemistry program in the Division of Materials Research, polymer/nanoparticle composites are synthesized using crosslinkable polymer-grafted nanoparticles (PGNPs) containing large volume fractions of high refractive index nanoparticles. Systematic investigations of fundamental structure-property relationships are conducted to explain how the optical and mechanical properties of these materials are affected by the large amount of filler content. The target materials possess tunable refractive indices due to the controlled amount of inorganic content (up to 85 wt.%), but also possess superior mechanical properties that surpass the bare polymer alone. Specifically, the researchers study the following aspects I) Developing materials-versatile protocols to synthesize and crosslink PGNPs with different inorganic nanoparticle and polymer compositions, II) Fully characterizing the mechanical and optical properties of the resulting structures, and III) Developing methods to induce photonic band gap architectures through ordered nanoparticle organization or multi-layer stacks of different composite compositions. The basic synthetic science and materials characterization efforts conducted enable a new class of optical materials, and also provide better design parameters for both grafting polymer brushes to inorganic particles and inducing covalent bond formation on nanoscale surfaces. This work advances both fundamental chemistry in solid state materials development and provides highly useful composites for optical devices.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.