Search

The petrol-based polymer has been widely applied in current daily life. The end-of-life of polymeric products has drawn environmental concerns. One of the solutions to such issues is to use bio-renewable materials to replace or reduce the use of petrol-based materials. Lignocellulosic materials are one of the potential candidates. Along with the features of 3D printing and the unique properties of biomass, 3D-printed biomass-based materials could be promising in preparing sustainable alternatives. In this dissertation, lignin and other biomass were applied to various 3D printing techniques for sustainable composites. Stereolithography (SLA) was first used, and the kraft softwood lignin was incorporated into the commercial clear resin. The printed composites showed a reinforcing effect after fully curing. Inspired by such a reinforcement, wood flour, where lignin is isolated, was also applied as a biomass filler. The 3D-printed wood flour composites showed a unique stress-whitening phenomenon, which displayed a potential for stress indicators. To further improve the loading amount of lignin in 3D printing, fused depositional modeling (FDM) was also involved. To improve the interfacial interaction between lignin and the polymer matrix, organosolv hardwood lignin was demethylated with improved phenolic hydroxyl groups. Enriched phenolic hydroxyl structures improved the interfacial interaction, thereby promoting tensile performance. A similar demethylation was executed on the softwood lignin. Due to the inherent difference in the functional groups, the obtained enriched polyphenol structures showed different but positive influences on tensile properties. In addition, the enhanced phenolic structures also showed great anti-aging performance, which brings more functions to the resultant composites, making lignin/polymer composites a promising functional and renewable material for the sustainable materials world.

In the first project, we describe the synthesis of an ambient stable high spin organic diradical 4 based on the Blatter moiety. The high-spin (S = 1) organic diradical 4, which consists of two Blatter radical moieties in a conjugated structure, exhibits a nearly exclusive population (88%) on triplet ground state at room temperature as a consequence of a large single-triplet energy gap (ΔEST = 0.5 kcal/mol). The target diradical molecule is synthesized over five steps with structural confirmation by single-crystal X-ray diffraction. The thermogravimetric analysis (TGA) shows the onset of decomposition at ~264 oC, indicating the diradical molecule has good thermal stability. The high spin organic molecules are not only purely organic magnets but also promising building blocks for emerging technologies. The diradical 4 crystal demonstrates good electrical conductivity. Also, the diradical can be evaporated under an ultra-high vacuum to form thin films, which are stable in ambient conditions for at least 18 h. In the second project, we describe the synthesis of a high-spin (S = 3/2) triBlatter triradical analogous to the diradical in the first project. The triradical was characterized by EPR, TGA, and UV-Vis near IR. Attempts to determine the ΔEDQ by EPR variable temperature measurement were performed. In the third project, we design and synthesize an organic radical MRI contrast agent. The structure of contrast agent is composed of a physiologically persistent nitroxide and a mannose sugar moiety. Taking advantage of the metabolic glycan labeling method, after the contrast agent was injected into mice, the nitroxides were expressed on the cell surface through metabolism, consequently changing the relativity of surrounding water molecules. Quantitative analysis of the in vivo NMR experiments and ex vivo EPR study were conducted. Advisor: Andrzej Rajca

Neuronal tracing methods are essential tools to understand the fundamental architecture of the neural circuits and their connection to the overall functional behavior of the brain. Various viral vectors have been developed to achieve cell-type specific and directional specific labeling of the neuronal connections. The incorporation of the viral tracers with optogenetics techniques can further provide precise control over the viral propagation. Herein, a novel approach to guide the infectious pattern of the Rabies Virus (RV) retrograde tracer with light is described. The key concept is to use Baculovirus (BV) as a helper virus to deliver all the functional components prior to the rabies infection. These functional components include the optogenetic tool parts, a fluorescent CRE reporter to mark RV infected cells, and other genes necessary for RV spread. GoldenGate DNA assembly method was used to efficiently construct three large BV expression cassettes in bacteria plasmids that can be transposed into the baculovirus genome in a single TN7 transposon recombination step. The actual imaging of BV and RV infected cells and stimulation of optogenetics tools for the spread of RV can be achieved with CMOS sensor and OLED display panels. By integrating these commercially available electronics with proper microcontrollers, a synchronized communication protocol for optogenetic stimulation, image capturing, and file transferring was established in a lensless imaging setup. The OLED and CMOS sensor’s large field of view and low cost allows this tracing method to scale many orders of magnitude greater than using microscopy-based methods.

The Rh-catalyzed, substrate directed catalytic asymmetric hydroboration of γ,δ-unsaturated amides provides a direct route to enantioenriched acyclic secondary γ-borylated carbonyl derivatives with high regio- and enantioselectivity. The catalytic condition optimization and substrate scope study is discussed, including the effects in catalytical asymmetric hydroboration on pre-installed chiral γ,δ-unsaturated amides. A mechanistic study from kinetic approach by graphical manipulation (reaction progress kinetic analysis for substrate orders and normalized time analysis for catalyst order.) was discussed in this thesis Advisor: Professor James M. Takacs