|dc.description.abstract||In recent years, metastable-state photoacids (mPAH) have been utilized to control
various chemical processes using visible light and have found many applications in
materials, energy, and biomedical areas. An introduction of metastable state
photoacid is given in Chapter 1.
In chapter 2, to clearly understand the relationship between the structures
and the physicochemical properties of mPAHs, a series of mPAHs were designed
and synthesized. The reversibility, stability, reverse reaction rate, and photoreaction
of the mPAHs were studied in detail using UV/VIS spectroscopy. The results
demonstrated that the electron-withdrawing groups on the electron-accepting
moiety enhance the overall photoreaction and stability of closed-ring form, while
the electron-donating group increase reversibility and decrease photoreaction.
In Chapter 3, a facile synthesis of merocyanine photoacid polymers without
using any protecting group is described. The polymers showed good photoactivity, high photoacidity, and were soluble in various solvents. Reversible patterning has
been demonstrated using a thin film of the polymer doped with methyl orange.
In Chapter 4, a novel mPAH with strong C-H acidity was described. The
pKa of its photoacidic state was experimentally determined and compared to a
commonly used mPAH. The photoacid showed low dark acidity and large pKa
change when irradiated by visible-light. The pKa for the photoinduced C-H acidity
is 4.8 units lower than that for the O-H acidity in the dark. These features together
with its easy preparation make it promise for the development of photoresponsive
materials based on proton transfer. Proton transfer between the photoacid and
proton acceptors with different pKas in solutions and polymer films was studied.
The photoacid showed superior properties in polymer films comparing to a
commonly used mPAH. Photochromic films with various color changes were
demonstrated as an example of potential application.
In the work described in Chapter 5, a series of mPAHs were designed and
synthesized, where chlorine was introduced to increase in the solubility and
photoacidity of indazol mPAH. Other works for increasing the activating
wavelength of the photosensitive molecules, photo release, and proton acceptors are
also described in this chapter.||en_US