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All these activities indicate the great attraction of the scientific community towards organic nonlinear optical materials as the key to future photonics. Last year the 3M Company announced a new blue light laser. It is interesting to note that Bell decided to end NLO research. But Japanese scientists have been very active in the field since 1982 and expect a great future for this emerging technology.

The panelists were asked the following questions:

(1) What is the main target? (2) How long will it take?

(3) What are the main difficulties to overcome?

1. D.J. Williams, "Organic polymeric

laboratory was involved in using clus- REFERENCES
ters in molecular beam epitaxy to make
layer-by-layer deposition of films. In
these films single molecules are aligned
up to a certain thickness. For example,
phthalocyanine molecules are aligned
up to five layers. After that they are not
aligned.

Major technical barriers stated by
the participants include low stability of
materials in the presence of light and
other environments, less than satisfac-
tory transparency and stability in fre-
quency doubling devices, connecting
optical fibers, preparation of defect free
large single crystals and their cutting
and polishing, and material availability
in general. Prof. Gunter stated that
lithium niobate was quite stable and
very good for waveguides in devices,
but the blue laser was on the horizon
and may present tough competition. In
the theoretical area, the present theories
of ß, X(2), and X(3) are quite useful for
guidance. But better models were
needed.

Burland stated that the frequency
doubler was the most important appli-
cation. It should be accomplished within
2 to 3 years. The blue light laser was
the major competition. Electro-optical
materials for switching and modulat-
ing must also be developed within the
next 2 to 3 years. In the next 2 to 3 years
2-3 GHz switches would be needed.
Khanarian said that poled polymer films CONCLUSIONS
had long range potential for low cost
integrated circuits. Making large sheets
of poled polymer films for displays has
a lot of potential. Shuto stated that
there were a large number of researchers
at NTT who were involved with NLO
investigations, including SHG mate-
rials, optical phase conjugation, and
optical computing. All had high hopes
for organic NLO materials. Yoshimura
said that his company had three
researchers working on optical switch-
ing. Miyata said that most companies
were concentrating their research on
second order nonlinear organic mate-
rials. The major difficulty of epitaxy
had to be solved. Sasabe said that his

For commercialization of some of
the potential devices, more time and
marketing have to be taken into account.

The main consensus was that research in the area of NLO organic materials is important as these materials have considerable potential for future photonic requirements. Major areas for additional emphasis include synthesis and preparation of single crystals and thin films of novel organic materials (using economically feasible processes); improvement of their stability, hyperpolarizability, and nonlinear optical efficiency; minimization of optical absorption for increasing the frequency doubling efficiency, and better theoretical models.

and non-polymeric materials with large optical nonlinearities," Agnew. Chem. Int. Ed. Engl. 23, 690 (1984).

2. K.D. Singer et al., “Second order nonlinear optical processes in orientationally ordered materials," J. Opt. Soc. Am. B4, 968 (1987).

3. J.L. Oudar et al., "Hyperpolarizabilities of nitroanilines and their relationship to the excited state dipole moment,” J. Chem. Phys. 66, 264 (1977).

4. J. Zyss, Nonlinear Optics 1, 1 (1991).

5. I. Ledoux et al., Chem. Phys. Lett. 172, 440 (1990).

6. C. Ye et al., Macromolecules 20, 2322 (1987).

7. D.M. Burland et al., "The design, synthesis and evaluation of chromophores for second harmonic generation in a polymer waveguide" (to be published).

Iqbal Ahmad is the director of the Army Research Office (ARO) Far East. He has a Ph.D. degree in physical chemistry from Imperial College, London, and is a Fellow of the Royal Society of Chemistry, London. Prior to his present position, Dr. Ahmad was a program manager in the area of materials science at ARO, Research Triangle Park, North Carolina.

U.S.-INDIA WORKSHOP ON FRONTIERS
OF RESEARCH IN POLYMERS
AND ADVANCED MATERIALS

Recent advances in polymer research as presented at the workshop are discussed.

BACKGROUND

An International Conference on the Frontiers of Polymer Research was held in Delhi in January 1991. The Army Research Office Far East (AROFE) was one of the sponsors. Because of the instability in the Gulf region, a number of important contributors to the conference could not attend. In spite of this there was considerable enthusiasm and interest in the advances in polymer research discussed at the conference. At the conclusion of the conference it was the general consensus that contributors who could not come to the conference be provided an opportunity to report their work at a workshop. So Dr. J.K. Nigam, Director of the Shriram Institute, Delhi, and Prof. P.N. Prasad, Director of the Photonic Laboratory, State University of New York, Buffalo, organized the U.S.-India Workshop on Frontiers of Research in Polymers and Advanced Materials at Goa on 6-9 January 1991. It was cosponsored by the Army Research Office Far East (AROFE) and the Shriram Institute. In all about 30 persons participated. The Proceedings will be published. In the following, only highlights of the workshop are briefly described.

DISCUSSION OF THE WORKSHOP

After the welcoming remarks by Dr. Nigam and introduction by Prof.

by Iqbal Ahmad

Prasad of the scope of the workshop, Dr. S.Z. Qasim, a member of the Planning Commission of R&D in India, formally inaugurated the workshop. Qasim is Director of the Indian Institute of Oceanography, Goa, and personally led the Indian research team to Antarctica last year. Mr. Dutt of the American Embassy in Delhi then described briefly the Indo-U.S. collaborative program. He stated that currently there were almost 200 ongoing projects in India, in which the Office of Naval Research (ONR), Naval Research Laboratory (NRL), National Science Foundation (NSF), Air Force Office of Scientific Research (AFOSR), and Department of Energy (DOE) collaborate with Indian scientists. These projects are supported by the Indian rupee fund to the tune of 200M rupees (about $8M). At this workshop a team from the Air Force consisting of Dr. Charles Lee (AFOSR), Dr. Ed Helminiak [(Wright Research and Development Center (WRDC)], and COL C. Dymek [European Office of Aerospace Research and Development (EOARD)] came to explore how AFOSR could tap the scientific resources of India with the help of Indian funds.

The workshop consisted of 10 sessions covering structural polymers, conducting polymers, polymers for integrated circuits (ICs), nonlinear optical polymer molecules, polymers

for aerospace applications, and polymer waste disposal.

Dr. C.K.N. Patel of AT&T Laboratories, in his keynote speech, gave an overview of polymers for photonics and electronics. He stated that the revenues from silicon-based electronics exceeded the oil revenues of the world and that silicon would continue to dominate the IC market for a long time. He projected that by 1995 the feature size of microelectronic ICs will be smaller than 0.3 micron, and the 64-MB DRAM will be commercialized by the end of the century. He explained the concept of "factory in bottle," which is essentially a new concept in which all operations on the substrate from the start to the finished state of the IC will be conducted without taking the substrate out of the controlled atmosphere at any time. He described the future potential of silicon-based polymers, particularly the polysylenes, which have a sheetlike structure and can be used to provide films of controlled refractive index and insulation properties.

The session on structural polymers was chaired by Dr. Helminiak, who is Chief of the Organic Polymers Branch at WRDC. In this session Dr. Bruno Fanconi of the National Institute of Standards and Technology (NIST), speaking on the issues and opportunities in high performance structural polymers, highlighted the critical barriers in the area of intelligent processing. He stated that the critical barriers

were the processing time, cost, and the durability of high performance polymers. He reviewed some of the ongoing work at NIST. This included modeling of the reaction injection molding of large composite components, which could be 30 to 40 feet long when used in advanced aircraft that are being designed for flying at 2.5 mach at a height of 30,000 feet. According to Fanconi, the challenges in these technologies include modeling of infiltration of heterogeneous preforms, three-dimensional (3D) flow, nonisothermal chemical reactions, and nonlinear rheology. Process monitoring is another area of importance. Aromatic heterocyclic polymers were the subject of the talk by Bob Evers of WRDC. He described studies of the application of high performance polymers in advanced aircraft such as the AV88, which is a modified version of the British Harrier. He said that while F-15 and F-18 aircraft contained 2% and 10% nonmetallic materials, AV88 had 27% organic polymers and their composites and predicted that future advanced fighter aircraft may have as much as 40% nonmetallic materials. He briefly discussed the polybenzothiozole (PBT) developed under Air Force contract and now picked up for further development by DuPont. Another new polymer that is under development at WRDC is benzocyclobutene, which shows thermal stability up to 500 to 600 °F. Blends of benzocyclobutenes and bismaleimide also show considerable thermal stability. One of the newest and most promising polymers that is drawing considerable attention is 6F-PBOS, which is a polybenzooxazole. Recently new synthesis processes of this polymer both by the Japanese and IBM have been reported. Evers also presented some experimental data on molecular composites, such as nylon plus 60% PBT. This composite has superior elasticity and strength, but low elongation. Commenting on the thermoplastic polymers, he said

that the problem areas were high cost and low use temperature.

Prof. Alan MacDiarmid, the coinventor of the first conducting polymer series, polyanilines, gave an excellent overview of the state of the art. He said that the research activity on conducting polymers was increasing very rapidly. For example, in 1991 the number of patents granted was as high as 281 as compared with 106 in 1986. Also during the last 12 months, Allied Signals has started manufacturing blends of polyanilines, which make them available to researchers in larger quantities. This should accelerate the progress of this potentially very fertile field. MacDiarmid described his latest results on the synthesis of high molecular weight polyaniline. However, the data shown did not indicate any dramatic improvement in the electrical conductivity with the increase in molecular weight. Prof. Epstein of Ohio State University, who holds a dual position as Professor of Chemistry and Professor of Physics and is at the same time Director of the Materials Research Center, gave a stimulating paper on the electrical conductance and magnetic susceptibility of polymers and discussed the synthesis

c

and properties of deca-methyland properties of deca-methylferrocene, which he codiscovered with one of his graduate students. The compound had a T of 4.8 K. New compounds such as V(CH),TCNE synthesized by his group have shown a T of 35 K, which is very encouraging advancement in the field of magnetic advancement in the field of magnetic polymers. Prof. James Mark of the University of Cincinnati presented results of his study on high performance films from semiflexible polymers, and Dr. Nigam reviewed the synthesis and market trends of inorganic fibers used in the polymer industry either as fillers or reinforcements.

In the session chaired by Dr. Dymek (EOARD), two interesting papers came from the Indian laboratories. Dr. Mittal from the Bhaba Atomic Research Center, Bombay, described a new

radiation-induced polymerization technique in which redox reactions can be induced in sensitive biosystems by exposing them to a gamma ray source, without the danger of introducing any contamination from the products of reaction. Mittal described a number of applications in which this technique was used. One of the most interesting was the development of a fast and cheap technique for detecting bilirubin needed to test for hepatitis. According to Mittal, it was almost like a litmus paper test and did not cost more than 50 pisa (2 pennies per test kit). The test kits have been distributed in a large number of Indian villages. Dr. Lal, Deputy Director of the National Physical Laboratory, Delhi, reviewed the various advanced analytical techniques available at his laboratories for the characterization of materials.

Photonics was the focus of the session chaired by Dr. Gallagher Daggit of the United Kingdom. Prof. Prasad gave a review paper on "Molecular Materials and Structural Property Relationship for Photonics." He stated that photonics is essentially light wave technology, used for processing and storing of information. This includes optical transmission, optical sensors, lasers, and photoactive components. The advantages of using photonics instead of electronics for data processing and storage include faster speed, larger volume of information processed, and insensitivity to electromagnetic interference. For optical switching required for optical processing of information, one needs to use nonlinear optical effects that allow the manipulation of light propagation by the application of the electric field or laser pulse. In addition, nonlinear optical effects give rise to frequency conversion such as frequency doubling for high density optical data storage and image analysis. Prasad discussed some of the work of his laboratories on PBT and polyphenylene vinyl (PPV). The latter polymer film on stretching develops molecular

orientation, which influences the third
order nonlinear coefficient. Prasad's
group has developed a sol gel process
for preparing silica polymer composite,
which has a combination of superior
low loss transmission character of glass
and high third order nonlinear coeffi-
cient of the polymer. The sol gel tech-
nique used is described in his paper
reported in the Materials Research
Society (MRS) Symposium Proceed-
ings Volume 175. While MacDiarmid
and others discussed polymers in which
the electrical conductivity depends on
the presence of delocalized pi elec-
trons, Dr. Höchstrasse of the Univer-
sity of Pennsylvania described the
mechanism of conduction of poly-di-
hexyl-silane in which the conductivity
is due to the delocalized sigma bonds
and the presence of rigid segments.
Prof. Larry Dalton of the University of
Southern California, Los Angeles, gave
an excellent paper on the photo-induced
micropatterning in organic polymers.
The major message of his talk was that
through photo-induced cross linking
certain polymers, such as azobenzenes,
show as good or better nonlinear opti-
cal behavior than the inorganic non-
linear optical materials such as lithium
niobate. This is an exciting result for CONCLUSIONS
researchers engaged in developing
nonlinear optical organic polymers.

reported by him was that of Dr.
Venkatachalam, who has synthesized a
3D pthalocyanine polymer. This poly-
mer is expected to have unique proper-
ties, which are being investigated. Dr.
Singh of the National Aeronautical
Laboratories, Bangalore, described the
facilities of the institute for the fabrica-
tion and testing of organic polymer
composites needed for aircraft struc-
tures. Finally, in the concluding talk,
Dr. Dhabolkar of the Shriram Institute
gave an interesting exposé of the sub-
ject of polymer waste disposal. He stated
that unlike developed nations, there
was no major polymer waste in India.
In fact, keeping in mind the low living
standards of India, some of the waste
products such as old tires, which are
disposed of by incineration in devel-
oped countries, can be used in India in
many ways. For example, they are used
in village carts and then as shoes for the
villagers. He pleaded that developed
nations must keep in mind the needs of
less developed nations when they embark
on large waste disposal programs. In
the case of polymer waste disposal, their
approach may not be applicable to third
world countries.

Dr. Krishnamurthy of the Vikrim Sarabhai Space Center, Trivandarum, described some of the laboratory facilities at his center and stated that most of the polymers and composites used in the two-stage launch rocket for placing Indian satellites in space were manufactured by the center, either in their own laboratories or on contract with the Indian industry. He stated that his laboratory had excellent capabilities in organic synthesis. Although they were not doing too much in conducting polymers, as in the context of the Indian environment, these materials are not in demand; however, some work done in basic synthetic chemistry was relevant. One of the outstanding efforts

In the concluding panel discussion, which was chaired by Dr. Charles Lee of AFOSR, the major topic discussed was the opportunities for U.S.-India collaborative research, in which the rupee fund could be used effectively. Lee stated that AFOSR would like to participate in the collaborative programs with Indian scientists, as ONR and NSF are doing. Such projects should be mutually beneficial. He encouraged the Indian scientists to contact AFOSR, indicating their expertise and ideas for collaboration. AFOSR would get them in touch with the right persons in their research laboratories. They could then jointly develop a research proposal, which would be evaluated for technical merit and relevance to the needs of

India and the AFOSR programs. Such proposals will be limited to only basic research areas, which would minimize problems related with intellectual property rights. In developing such proposals, if there is a need for an Indian scientist to visit an Air Force laboratory, it could be arranged through the EOARD Window on Science program. I represented the position of ARO and promised to explore with ARO participation in a similar manner in areas of research that are relevant to the research and development (R&D) programs of the Army. Dr. Lee also offered to coordinate with ARO as the joint program evolved and refer proposals (Indo-AFOSR) to ARO for information, cosponsorship, or ARO show of interest.

Dr. MacDiarmid offered suggestions in which Indian scientists can initiate new projects. The suggestions included synthesis of derivatives of known advanced conducting polymers and study of mechanisms and properties. Dr. Prasad suggested chemical synthesis of nonoptical organic materials and the study of their property structure relationship. Some of the characterization may need sophisticated equipment, which may not be available in India. The collaborator in the United States would work in that area.

On the whole, the attendees of the workshop, particularly the Indian scientists, were very enthusiastic about the collaborative program. From the triservice point of view, it is a window of opportunity, as with little effort and almost no dollar investment highly qualified scientists in India can be made available to work on selected Department of Defense R&D programs. Indian scientists are very good at theoretical studies because of the very high standards of education in mathematics. They are also very well versed in chemical synthesis, computer software, and theoretical physics. These resources can be effectively utilized to the mutual benefit of the two countries.

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