The objective of this research project is to better understand the structure-property relationship in polymer nanocomposites (PNCs). The results from this project can then be used to guide future PNC design. PNCs have attracted substantial attention since the first reports in 1980s. Nanofillers with at least one dimension below 100 nm have been included in polymeric matrices at relatively low volume additions (< 5%), leading to profound property enhancements of the polymer. To better understand the structure-property relationship in PNCs, it is critical to obtain controlled particle aggregates in a PNC system with defined size and size distribution. In this research, the PI aims to use novel Janus nanoparticles (JNPs) coated with polymer brushes as the model particle system to form PNCs. Using JNPs instead of symmetrically functionalized nanoparticles, well defined nanoparticle ensembles in the polymer matrix can be achieved; hence JNP nanocomposites provide a unique and unprecedented model system to decouple the interface and structural effects. The correlation between particle ensemble structure and mechanical properties of PNCs will therefore be unambiguously established. This research is the first to systematically study the aggregation of JNPs in polymeric matrixes. Furthermore, many other properties of PNCs such as electrical, optical properties are also largely dependent on nanoparticle aggregation. Therefore, this research will also benefit using PNCs in other advanced applications.
PNC is a fast growing field which has dramatic impacts on our daily life. PNC can lead to stronger, lighter, less expensive materials for various applications ranging from aircraft to sporting goods. This research, if successful, will dramatically impact the nanoparticle and PNC research field because it could help design and synthesize PNCs in a more controlled and efficient way. PNCs with enhanced performance can therefore be fabricated. The educational component of the project includes: (1) mentoring graduate, undergraduate students and post-doc researchers; (2) updating/developing graduate courses; and (3) involving high school students and teachers, particularly under-represented populations, in the research activities.
In the proposed research, we have systematically investigated synthesis and self assembly of novel Janus nanoparticles (JNPs). Janus particles, named after the Roman god Janus with two faces towards opposite directions, represent a category of objects possessing a noncentrosymmetric structure, often with a single core that is surrounded by compartmentalized corona. Because of their unique structures and extraordinary properties, Janus particles have attracted increasing attention. As a unique type of hybrid materials, Janus particles are promising in the fields such as photonics, sensors, drug delivery and surfactant. Because of the anisotropy, these particles can be amphiphilic and resembles the properties of soap molecules: with both hydrophobic and hydrophilic end. We developed a novel means to synthesize these particles using polymer single crystals. We further showed that these assemblies possessed novel properties and could find applications in catalysis, surface enhance Raman spectroscopy and artificial nanomotors. Because the particle surfaces are formed by polymer chains, their conformation, as well as the corresponding assembles, can be responsive to external stimuli such as pH, temerature and/or solvents. Our method is generally applicable to different nanoparticle systems as long as the properly designed system meets the following requirement: specific interaction between the first adsorbed nanoparticle and polymer single crystals, and specific interaction between the second adsorbed nanoparticle and the first adsorbed nanoparticle. Our work tackles a challenging problem in the nanotechnology field. We envisage that the project will lead to a library of unprecedented nanoparticle structures for both fundamental scientific study and technological applications.
