Printing of
3-dimensional nanostructures with high-resolution by two-photon polymerization
has gained significant attention recently. Isopropyl thioxanthone (ITX) has
been studied and used as a photoinitiator because of its unique property in
initiating and depleting polymerization, but to further improve the resolution
of 3D structures, new photoinitiating materials are necessary to decrease the
power requirements especially in industrial world. In this dissertation, different
new types of thioxanthone-based photoinitiators were synthesized and our new
initiators possessed a clear enhancement in terms of excitation over ITX. To clearly
reveal the writing mechanism behind it, the behavior of the initiators was
evaluated by several methods such as low temperature phosphorescence
spectroscopy and density functional theory (DFT) calculations. The first type
of new molecules with alkyne bridge will be discussed in chapter 2 and the
further developed initiators with electron donating and withdrawing groups will
be discussed in chapter 3. By modifying the structure of ITX, we have revealed
and proposed an important pathway to guide future development of
photoinitiators in direct laser writing.