الفهرس 
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Abstract
Photochromism is a reversible transformation
between two geometrical isomers with an observable change
in the absorption spectrum upon exposure to
electromagnetic radiation. Organic photochromic
compounds have received considerable attention in the
recent decades because of their wide applications in
information storage, electronic display systems, sensors,
photochromic glasses and optical switching devices.
Spiropyrans belong to the famous families of photochromic
materials. This thesis deals with studying the photochromic
properties of SP (1’,3’-Dihydro-8-methoxy-1’,3’,3’-trimethyl-
6-nitrospiro[2H-1-benzopyran-2,2’-(2H)-indole]). In the
photocoloration reaction of the SP by UV irradiation the
closed spiro form will transform to the open MC form by CO
bond cleavage . The back reaction occurs spontaneously.
Both reactions were studied in different media such as some
polar solvents, non-polar solvents, polymer matrix. The
different kinetic parameters such as the rate constant of both
the photocoloration and the dark reactions and the half life
time of MC are measured in the different environments.
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The thesis includes 3 chapters:
Chapter one: This chapter contains a general
introduction on photochromism, some families of
photochromic materials, and different applications of
photochromism.
Chapter two: This chapter includes the materials,
instrumentation, general procedures, methods of data
analysis, and representation using origin version 9.
Chapter three: This chapter contains the obtained results and
discussion.
This chapter deals with studying the photochromic
phenomena of the SP 1’,3’-Dihydro-8-methoxy-1’,3’,3’-
trimethyl-6-nitrospiro[2H-1-benzopyran-2,2’-(2H)-indole]
where its absorption spectrum in ethanol has two bands in
UV region at 278 nm and 359 nm and one peak in the
visible region at 563 nm.
The effect of polarity of the organic solvents on the
photochromism and the absorption spectrum of the
spiropyran was studied. It was found that in polar solvents
such as ethanol the intensity of the merocyanine band
increases and in non-polar solvents such as cyclohexane the
merocyanine band disappears. SP exhibits negative
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solvatochromism because it was found that by increasing
the solvent polarity the MC peak is blue shifted.
The addition of lanthanide metal ions(Sm3+,Tb3+,Gd3+) to
the ligand solution leads to an increase in the intensity of the
merocyanine band with a blue shift by around 100 nm . This is
an indication for the complex formation.
The incorporation of the SP into polymeric matrix
makes it easy for the photochromic SP to be applicable. The
SP-PMMA film can be used as sensor for the solvent
polarity.
The effect of UV irradiation time on the absorption
spectrum of the SP in polar solvents, non-polar solvents, in
mixed solvents’ system of non-polar and polar solvents and
PMMA film was studied. By increasing the UV irradiation
time the spiro form transformed to the MC form . Also the
dark reaction was studied in these media where the MC
returns back to the closed form again.
The effect of UV irradiation time on the absorption
spectrum of the SP after the addition of lanthanide metal
ions in non-polar solvent and the back reaction were
studied.
The effect of increasing the polarity of the solvent,
rigidity of the medium, the polymerization, and the
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complexation on the kinetics of the color developing
reaction and the back reaction were studied. The highest
half life time for the MC was in the case of the PMMA film.
The addition of the lanthanide metal ions highly stabilize the
MC form. A polar solvent promotes the formation of the
open MC form.
A complete switching cycle with this photochromic
compound can be completed on a second timescale in case
of non-polar solvents and on a minute timescale in rigid
PMMA matrix .