FIELD OF INVENTION:
This invention relates to a novel m-nitroaniline doped PES and optically active
guest-host polymer.
Further the invention also relates to a process of preparing novel m-nitroaniline
doped PES and the optically active polymer.
BACKGROUND OF THE INVENTION:
Optical communication systems are increasingly displacing electronic methods
because of their speed, bandwidth and reliability. However, at present they suffer
from the difficulty that all optical switching and routing are not possible on a
microcircuit-sized scale. This problem arises from the rather low values of the
electro-optic coefficients of currently favored materia1s. For several years now,
attention has been focused on organic materials as a solution to this problem.
The search for superlative organic materials begins, therefore, with the search for
molecules with large non-linear responses. Today, literally hundreds of organa
polymeric materials have found widespread use in the manufacture of
microwave, electronic and photonic systems. This is also due in part to their
structures that can be tailored to provide a wide range of physical properties, and
also due to the ease of processing and fabrication of polymers.
For the design of organic materials suited for use in optoelectronic devices, nonlinear
optical (NLO) chromophores incorporated in amorphous polymers based
on the Guest-Host systems are subject to intense research activities. Such
materials have numerous advantages as compared to the crystalline materials.
Large area devices having desired organa-polymeric molecular structures in a
thin film form can be produced for various optoelctronic and photonic
applications.
-2-
The ideal organic material that could have potential application in NLO devices
should possess combination of physiochemical characteristic properties as
follows:
1. Non-Centro symmetric Molecular design
2. Optical transparency
3. Ease of Fabrication
4. Non toxicity and good environmental stability
5. Ability to process into crystals and thin films
6. Architectural flexibility for molecular design and morphology
7. High mechanical strength and thermal stability
8. Large non linear figure of merit for frequency conversion
9. High Laser damage threshold
10. Fast optical response time
11. Wide phase matchable angle
Recent growing efforts in molecular engineering suggests that' organic NLO
materials possess comparable better NLO properties than inorganic materials,
hence, their tremendous practical potential have been anticipated. The aim of the
study of organic NLO chromophore-doped polymers is to replace their inorganic
counterparts.
Nonlinear-optics is an important field of photonics whose technology includes
acquisition, storage, process, and transmission of photons in signal generation
and processing. Organic nonlinear optical (NLO) materials provide strong
potential advantages for the second harmonic generation (SHG) and electrooptic
(E-0) applications. Particularly, poled polymeric systems have attracted
-3-
remarkable interest in recent years as promising candidates for application in EO
and photonic devices. The second-order NLO polymeric devices require that
the poled order be quite stable on time of the order of years and therefore studies
on polar order relaxation became more and more important for pradical
application.
Nonlinear optical materials are those with an index of refraction that can be
altered in the presence of laser light. Nonlinear optics provides a fascinating
window through which to view the interaction between atomic /molecular systems
and coherent radiation as well as offering a wealth of technological applications
in optical data storage, optical communications, and wavelength conversion.
Photorefradive materials are distinguished from other nonlinear optical materials
by their ability to generate large index of refraction changes in response to
relatively low power, visible laser light.
Nonlinear optical properties are a sensitive probe of the electronic and solid-state
structure of organic compounds and as a consequence find various applications
in many areas of optoelectronics including optical communications, laser
scanning and control functions, and integrated optics technology. Because of
their strongly delocalized electronic systems, polymeric and non-polymeric
aromatic compounds show highly nonlinear optical effects. Nowadays, polymer
chemists are able to tailor specific materials properties for various applications.
Some organic substances with electronic systems exhibit the largest known
nonlinear coefficients, often considerably larger than those of the more
conventional inorganic dielectric and semiconductors, and thus show promise for
thin-film fabrication, allowing the enormous function and cost advantages of
integrated electronic circuitry. The electronic origins of nonlinear optical effects in
organic electronic systems are reviewed, with special emphasis being given to
second-order nonlinear optical effects.
-4-
Polymers with guest-host system have been investigated to increase the content
of NLO chromophores in second order nonlinear optics. Though very low poling
temperature has been applied, the observed UV absorption difference before and
after poling was large due to low glass transition temperature of the polymer and
high content of chromophores introduced by guest molecules. The reaction
between polymer matrix and chromophore was confimed by FT-IR and NMR
spectroscopy.
It has been reported that combinations have many advantages over other
systems, especially in terms of high thermal stability and less degree of
relaxation of oriented chromophores in second order nonlinear optics (NLO). In
order to prevent the randomization of the poled NLO chromophores that limit the
lifetime of poled polymer devices the usually NLO chromophores are
incorporated into matrices by crosslink reaction. The resultant incorporated
chromophores then display distinct advantages over physically incorporated
guest-host polymer systems. Such an increase can be attained via the formation
of interchain chemical bonds, resulting in the partial immobilization of organic
chromophores in the resultant cross linked polymer matrices. Here, the desired
overall effectiveness (i.e. decrease in the mobility of organic chromophores in a
polymer matrix) strongly depends on both the number and nature of available
cross-linkable sites.
Enhanced NLO properties were attained by increasing the mobility using
polymers of low glass transition temperature and by a suitably adjusting the
content of chromophores to prevent phase separation. Organic polymers
combine the NLO properties of conjugated electron systems with the feasibility of
molecular engineering i.e. creating new systems with appropriate structural,
optical and molecular properties to meet the wide requirements of
-5-
optoelectronics device applications. Optical nonlinearity is primarily molecular in
nature.
OBJECTS OF THE INVENTION:
An object of this invention is to propose novel m-nitroaniline doped PES and
optically active guest-host polymer. Further the invention also relates to a
process of preparing novel m-nitroaniline doped PES and the optically active
polymer;
Another object of this invention is to propose a novel m-nitroaniline doped PES
and optically active guest-host polymer having large, non-resonant linearities,
broadband coefficients;
Still further object of this invention is to propose a novel m-nitroaniline doped
PES having low dielectric constants;
Still another object of this invention is to propose a novel m-nitroaniline PES
having relatively constant refractive index for wavelength from infrared to
microwave region and thus ensures proper modulator operation over the range;
Further object of this invention is to propose a novel m-nitroaniline doped PES
Ultra-fast response times;
Still further object of this invention is to propose a novel m-nitroaniline doped
PES Low optical loss;
Yet another object of this invention is to propose a novel m-nitroaniline doped
PES high levels of integration into optical packages;
-6-
Further object of this invention is to propose a novel m-nitroaniline doped PES
having resistance to shear, shock and electricity;
Still further object of this invention is to propose a novel m-nitroaniline doped
PES having chemical stability and dimensional stability;
Still further object of this invention is to propose a novel m-nitroaniline doped
PES with low cost materials leading to cheap method.
Another further object of this invention is to propose a process for addition of
chromophore composition upto 20% with respect to host PES.
A still another further object of this invention is to propose frequency conversion
of laser light from red to green light after passing through transparent film.
DESCRIPTION OF THE INVENTION:
According to this invention there is provided A novel m-nitroaniline doped
polyether Sulfone (PES) and optically active guest-host polymer is susceptible to
generate non-linear optically (NLO) active properties that doubles the frequency
of light incident upon such materials.
In accordance with this invention there is also provided of A process for the
preparation for m-nitroaniline doped polyether sulfone (PES) and optically active
guest host polymer comprising;
dissolving polyether sulfone (PES) alongwith 1-20 wt % m-NA in organic solvent
under stirring to obtain clear solution;
-7-
subjecting the solution to the step of solution casting evaporating the solvent
under ambient conditions till the film hardens;
placing the film in vacuum oven to remove all the residual solvent.
An important feature in the development of Guest-Host systems, is the control of
primary NLO susceptibities or coefficients of the NLO chromophore and the
secondary properties of organic polymers such as solubility, processability,
optical clarity, absorption, thermal stability, etc. with the proper molecular
engineering. A photorefractive polymer composite is constructed by doping a
photo conducting polymer matrix with a nonlinear optical molecule (or
"chromophore"). Fabrication of a typical composite begins with the synthesis of
the chromophore using standard azo coupling and SN2 reactions. The
chromophore is then blended with a commercially available photoconducting
polymer.
Polyethersulphone (PES) in optoelectronics
Physical, chemical and optical properties ofPES
Chemical Resistance
Acids-Concentrated
Acids-dilute
Alcohols
Alkalis
Aromatic Hydrocarbons
Greases and Oils
Halogens
Ketones
Fair
Good
Good
Good
Fair
Good
Good
Poor
Electrical Properties
Dielectric constant @1MHz
Dielectric strength (kV.mm-1
)
Dissipation factor @ 1 MHz
Volume resistivity (Ohm.cm)
Mechanical Propeties
-8-
Abrasive resistance-ASTM D1044 (mg/1000 cycles)
Elongation at break(%)
Hardness-Rockwell
lzod impact strength (J.m-1
)
Poisson's ratio
Tensile modulus (Gpa)
Tensile strength (Mpa)
Physical Propeties
Density (g.cm-3
)
Flammability
Limiting oxygen index (%)
Radiation ~esistance -Alpha
Refractive index
Resistance to Ultra-violet
Water absorption-equilibrium(%)
Water absorption-over 24 hours(%)
Thermal Properties
Coefficient of thermal expansion (x1 0~ K-1
)
Heat-deflection temperature-0.45Mpa (°C)
Heat-deflection temperature- 1.8Mpa (°C)
Lower working temperature (°C)
Thermal conductivity (W.m-1.K-1
)
Upper working temperature (°C)
Properties Polyethersulphone Film
3.7
16
0.003
1017
6
40-80
M88
85
0.4
2.4-2.6
70-95
1.37
V-0@
0.4mm
34-41
Good
1.65
Fair
2.2
0.4-1
55
>260
203
-110
0.13-0.18@
23
180-220
J
1 ;l
-9-
Property Value
Dielectric Constant @ 1 MHz
Dielectric Strength @251Jm thick kV.mm-1
3.7
232
Dissipation Factor @1 MHz 0.012
Elongation at Break
Flammability
Heat-sealing Temperature
Initial Tear Strength
%
Permeability to Carbon Dioxide @25°C
Permeability to Oxygen @25°C
Permeability to Water @25°C
Specific Heat
PES as the potential host
20-150
VTM-0@
251Jm
259-287
g.IJm-1 7.5-16.9
x1013 cm3.cm.cm-2.s-1.Pa-1 1.8
x10-13 cm3.cm.cm-2.s-1.Pa-1 0.4
x1 013 cm3.cm.cm-2.s-1.Pa-1 75
kJ.kg-1 .K-1 1.1
Polyethersulphone (PES) has been known as a versatile commercial high
performance polymer (Commercial Product of Gharda Chemical Co.Ltd.,
Mumbai) that features with relatively high thermal stability up to 180°C has an
ability to retain many mechanical and electrical properties upto 210°C, good
moldability, transparency, rigidity, fire resistance, low dielectric constant and low
water absorption. Almost all the processing methods like extrusion, casting,
bending and joining etc. are possible. These features have attracted this polymer
to be a favorable host.
-10-
STRUCTURE OF PES:
0
II 0 s
II 0
n
Fig.1.1 ·
BOND ANGLES:
0
- c 11 c-
""s/
M 105'0
Fig.1.2 Fig.1.3
PES can be synthesized and developed by both elctrophilic and nucleophilic
substitutions.
The Guest: meta-Nitroaniline
Meta-Nitroaniline (m-NA) is a substituted amine, with a weak basicity than
aniline. The various graphical representatio·ns of m NA are shown as follows:
-11-
+~0
N,_
0
Fig.1.4 Lewis structure of m-NA
0"-.+~0
N
Fig.1. 7 .Resonant forms of m-NA
As far as the chemical nature of nitroaniline is concerned, the basicity is due to
the strong-R effect, additionally the nitro group also has -1 effect due to the
positive charge on the N-atom. This -1 effect tends to draw the lone pair with
consequent decrease in the basicity.
-12-
The realized nonlinearity of meta-Nitroaniline and the optical as well as material
advantages of PES, a Guest-Host system based m-NA and PES is taken as the
project work. The present invention relates to develop m-Nitroaniline doped PES
as a novel and optically active Guest-Host system for optoelectronics
applications with the following unique features:
• Utilization of thermally stable PES as Host material.
• Preparation of freestanding doped m-NA/PES films for SHG investigation.
• Formulation and establishment of novel and unique combination of highly
active NLO moiety (m-NA) with PES through proper materials engineering.
• Preliminary attempt to combine/modify/ minimize and to manifest the trade
off between the m-NA and PES and to evaluate its optoelectronics
feasibilities.
• Optimizing the SHG intensities generated from the polar m-NAIPES
system for possible optoelectronics device applications.
Polymeric materials for Non Linear Optics (NLO) have been identified for
emerging advanced materials for photonic technologies. These materials consist
of molecular fragments displaying NLO activity or colored organic chromophores
(Guests) dissolved in or covalently attached to a polymeric (host) material. NLO
is concerned with the interaction of electromagnetic fields generally in the optical
frequency range. NLO guest-host polymers have the ease of fabrication into such
device structures. One of the most interestingly and technologically promising
phenomenon is the light modulation of the index of refraction of the material
through the photo refractive effect. NLO active chromophores were incorporated
into an amorphous polymer by doping. Here the non-linear molecule is not
attached to the polymer chain and hence can rotate freely close to the glass
transition temperature. The attractive feature of the guest-host systems is its
-13-
ease of preparation. They offer several advantages in that they can be used for a
wide variety of centro-symmetric NLO chromophores for Second Harmonic
Generation (SHG) activity, ease of processing into thin films by coating, dipping
and lithography, ease of fabrication, inexpensive production of NLO materials,
wide range of operating frequencies and low dielectric constant.
Structurally designed polymers have been identified as a useful optoelectronics
material for optical device applications as they exhibit flexibility in processing and
fabrication ease of designing various futuristic NLO devices. Conjugated donoracceptor
organic systems offer large nonlinear effects and it is widely used in
potentially high speed electro-optical devices. Designed Guest-Host systems are
replacing their inorganic counterparts due to the intrinsic tailor ability that can be
achieved through materials engineering. These devices are typically made of
depositing thin films of polymer on substrates such as metallized glass slides,
silicon, or semiconductor wafers. SHG is a second-order non-linear effect where
the frequency of the Nd:YAG laser beam is doubled (i.e. the wavelength is
halved from 1064 to 532 nm) and this output frequency can be utilized for various
optoelectronics applications. The conversion of frequency occurs due to
materials ability to change its refractive index and thus altering the frequency of
light passing through it. The interest in NLO materials based on organic polymers
is due to the demonstrated possibilities of large non-resonant susceptibilities,
ultra fast response time, low dielectric constant and high optical damage
threshold. This is evident from the development of wave-guide and other optical
devices from polymeric materials such as polystyrene. Recently NLO effects
such as SHG have been observed by Negi et al. in simple organic polymers
when doping NLO active chromophores like m-NA, 2-methyl-4-nitroaniline (2-
MNA) in Polystyrene and PMMA. Recently, design of organic materials for use in
optoelectronic devices, non-linear optical (NLO) chromophores incorporated in
amorphous polymers based on the Guest-Host systems are subject to intense
research activities. These preliminary investigations confirm the feasibilities of
-14-
this system to emerge as a new frequency doubling material in the area of
optoelectronics (R.K. Goyal, P.V. Adhyapak, S.R. Damkale, M. Islam, R.C. Aiyer,
and Y.S. Negi, (2004) Int. J. Plastic Techn., 8, 249., Y.S. Negi,; R.K. Goyal,; M.S.
Sureshkumar,; R.C. Aiyer,; (2004) lntemational patent (to Department of
Information Technology, New Delhi, India), Oct 10, (Filed).,Y.S. Negi,; R.K.
Goyal,; M.S. Sureshkumar,; M. Islam,; R.C. Aiyer; Proc. National conference on
Microwaves and optoelectronics, held in June 29-30, (2004) Dr. Babasaheb
Ambedkar Marathwada University, Aurangabad, India, 397,(c) Anamaya
Publisher, Anshan Publishing Co. Pvt. Ltd., UK (In Press)).
GENERAL METHOD OF PREPARATION AND CHARACTERIZATION: PES
was dissolved in chlorinated hydrocarbons or high boiling organic solvents to
make viscous film forming solution. m-NAIPES was also prepared by using
chlorinated hydrocarbons or high boiling organic solvents to make viscous film
forming solution. PES incorporated with 1 to 20 wt% m-NA was prepared by
dissolving both in suitable organic solvent and stirred well for a 1-2 h. After
getting clear solution, films were prepared by solution casting method onto a
glass plate. The solvent is allowed to evaporate under ambient conditions until
the film hardens. The film is then removed and placed in vacuum oven for 2 h at
75°C to remove all the residual solvent. After drying, the films are characterized
by SHG, UV-Vis, FT-IR, XRD, SEM and thermogravimetric analysis. For SHG
measurement the films are poled before measuring second harmonic generation.
For SHG measurement the films were done using Nd:YAG laser. An output of 25
mJ is obtained for an input of 6 mJ. The film showed Amax at 386.5 to 410 nm.
SHG intensity values infer that pure PES film does not show a SHG due to
centro-symmetricity. FT-IR spectroscopy of PES shows bands for ether (-C-0-
C-), -CH2 bending, -S=O bond; m-NA shows absorption band for -N02 stretching,
asymmetric stretching of -NH2, symmetric stretching of NH2, N-H bending, N-H
stretching, whereas the doped sample contain bands corresponding to both m-
15-
NA and PES and thus confinning doping. Shifting of the major peaks observed
depending on the %age of dopant. This centro-symmetricity is destroyed in the
poled doped films by the incorporation of PES with the m-NA. The SHG intensity
of the doped films increases as the percentage of dopant is increased in the PES
matrix. Also, for a given composition, SHG intensity increases with increase in
input energy. m-NA doped PES system appears yellow in color and the color
deepens as the percentage of the dopant is increased. PES control and doped
PES bulk films characterized by SEM showed insignificant difference of the film
surfaces. No aggregation observed even upto 20% doping which promises a
wider range of enhancement of various properties and their application. XRD
analysis confinns the amorphous nature of the PES system for both the doped
and undoped films. There is no phase aggregations observed even upto 20%
doping. % crystallinity of the doped polymer sample is higher than that of the
undoped samples. Thermal analysis using thermogravimetric analysis, we
observed that for PES film the onset of weight loss takes place at 500°C and
·maximum weight Joss at temperature 625°C, whereas for doped films the onset of
weight loss occurs at 475°C and maximum loss at 620°C. Thus we can say that
thermal stability of doped films decreases with increasing concentration of m-NA.
EXAMPLE
Example 1:
Film of PES incorporated with Owt% m-NA is prepared by dissolving both in
suitable organic solvent and stirred well for a 1-2 h. After getting clear solution,
films are prepared by solution casting method onto a glass plate. The solvent is
allowed to evaporate under ambient conditions until the film hardens. The film is
then removed and placed in vacuum oven for 2h at 75°C to remove all the
-16-
residual solvent. The film is denoted by So. After drying, the films are
characterized by SHG, UV-Vis and FT-IR. For SHG measurement the films were
poled. Pure PES film did not exhibit SHG phenomenon. PES itself is a white
amorphous powder, whose undoped film is colorless and transparent.
Example 2:
Film of PES incorporated with 1 wt% m-NA is prepared by dissolving both in high
boiling organic solvent and stirred well for a 1-2 h. After getting clear solution,
films are prepared by solution casting method onto a glass plate. The solvent is
allowed to evaporate under ambient conditions until the film hardens. The film is
then removed and placed in vacuum oven for 2h at 75°C to remove all the
residual solvent. The film is denoted by S-1. After drying, the films are
characterized by SHG, UV-Vis and FT-IR. UV-Vis Spectrophotometer of PES
showed 100% transmission of the light above 200 nm but in the case of m-NA
doped PES the shift is towards higher wavelength in the range of 310 to 500nm,
which is due to the high energy absorption by m-NA guest molecules. The
absorption peak was found in the range of 385-416 nm and shifts towards higher
wavelength as the % of dopant increases. For SHG measurement the films are
poled above glass transition temperature. The SHG results, at an applied voltage
of 30 V increases an input voltage of 6 mJ to 25 mJ. The film exhibited Amax of
386.5 nm, which is too far from the laser beam wavelength of 1064 nm
(Fundamental Wavelength) used for determining the SHG signal and output of 25
mJ is obtained for an input of 6 mJ.
Example 3:
As described in example 1, film of PES incorporated with 2 wt% m-NA is
prepared and characterized. The SHG results, at an applied voltage of 30 V
-17-
increases an input voltage of 6 mJ to 25 mJ. The film exhibited Amax of 387 nm,
which is too far from the laser beam wavelength of 1 064nm (Fundamental
Wavelength) used for determining the SHG signal. The SHG intensity of film
increases from 6 to 30 mJ.
Example4:
As described in example 1, film of PES incorporated with 4wt% m-NA is prepared
and characterized. The SHG results, at an applied voltage of 30 V increases an
input voltage of 6 mJ to 25 mJ. The film exhibited Amax of 386 nm, which is too far
from the laser beam wavelength of 1 064nm (Fundamental Wavelength) used for
determining the SHG signal. The SHG intensity of film increases from 6 to 40 mJ.
Example 5:
As described in example 1, film of PES incorporated with 6wt% m-NA is prepared
and characterized. The SHG results, at an applied voltage of 30 V increases an
input voltage of 6 mJ to 25 mJ. The film exhibited Amax of 385 nm, which is too far
from the laser beam wavelength of 1 064nm (Fundamental Wavelength) used for
determining the SHG signal. The SHG intensity of film increases from 6 to 50 mJ.
Example 6:
As described in example 1, film of PES incorporated with 1 Owt% m-NA is
prepared and characterized. The SHG results, at an applied voltage of 30 V
increases an input voltage of 6 mJ to 25 mJ. The film exhibited Amax of 396 nm,
which is too far from the laser beam wavelength of 1 064nm (Fundamental
-18-
Wavelength) used for determining the SHG signal. The SHG intensity of film
increases from 6 to 55 mJ.

WE CLAIM:
1. A novel m-nitroaniline doped polyether Sulfone (PES) and optically active
guest-host polymer is susceptible to generate non-linear optically (NLO)
active properties that doubles the frequency of light incident upon such
materials.
2. The m-nitroaniline doped polyether sulfone as claimed in claim 1
comprises 1 to 20 wt % of m-nitroaniline (m-NA) in the PES matrix.
3. The m-nitroaniline doped polyether sulfone and the polymer as claimed in
claim 1, wherein said polymer can increase the input energy of 6 mJ to 25
mJ.
4. A process for the preparation for m-nitroaniline doped polyether sulfone
(PES) and optically active guest host polymer comprising;
dissolving polyether sulfone (PES) alongwith 1-20 wt % m-NA in organic
solvent under stirring to obtain clear solution;
subjecting the solution to the step of solution casting evaporating the
solvent under ambient conditions till the film hardens;
placing the film in vacuum oven to remove all the residual solvent.
-20-
5. The process as claimed in claim 1, wherein the said mixture of PES, m-NA
and organic solvent il) stirred for 1 to 2 hrs.
6. The process as claimed in claim 1, wherein the said step of casting is
preferred on a glass plate to form the film.
7. The process as claimed in claim 1 wherein the said film is placed in
vacuum for 2 hrs at 75°C.
8. The novel m-nitroaniline doped polyether sulfone (PES) and optically
active guest-host polymer as claimed in claims 1 to 3 form material for
organic moleculars stitches, frequency converters and storage devices.