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All these activities indicate the great laboratory was involved in using clus- REFERENCES attraction of the scientific community ters in molecular beam epitaxy to make towards organic nonlinear optical layer-by-layer deposition of films. In 1. D.J. Williams, “Organic polymeric materials as the key to future photon- these films single molecules are aligned and non-polymeric materials with large ics. Last year the 3M Company up to a certain thickness. For example, optical nonlinearities,” Agnew. Chem. announced a new blue light laser. It is phthalocyanine molecules are aligned Int. Ed. Engl. 23, 690 (1984). interesting to note that Bell decided to up to five layers. After that they are not end NLO research. But Japanese scien- aligned.
2. K.D. Singer et al., "Second order tists have been very active in the field Major technical barriers stated by nonlinear optical processes in orientasince 1982 and expect a great future the participants include low stability of tionally ordered materials,"). Opt. Soc. for this emerging technology.
materials in the presence of light and Am. B4, 968 (1987). The panelists were asked the fol- other environments, less than satisfaclowing questions:
tory transparency and stability in fre- 3. J.L. Oudar et al., “Hyperpolariza
quency doubling devices, connecting bilities of nitroanilines and their rela(1) What is the main target?
optical fibers, preparation of defect free tionship to the excited state dipole
large single crystals and their cutting moment,”J. Chem. Phys. 66, 264 (1977). (2) How long will it take?
and polishing, and material availability
in general. Prof. Gunter stated that 4. J. Zyss, Nonlinear Optics 1,1 (1991). (3) What are the main difficulties to lithium niobate was quite stable and overcome?
very good for waveguides in devices, 5. I. Ledoux et al., Chem. Phys. Lett.
but the blue laser was on the horizon 172, 440 (1990). Burland stated that the frequency and may present tough competition. In doubler was the most important appli- the theoretical area, the present theories 6. C. Ye et al., Macromolecules 20, cation. It should be accomplished within of B, X(2), and X(3) are quite useful for 2322 (1987). 2 to 3 years. The blue light laser was guidance. But better models were the major competition. Electro-optical needed.
7. D.M. Burland et al., "The design, materials for switching and modulat- For commercialization of some of synthesis and evaluation of chromoing must also be developed within the the potential devices, more time and phores for second harmonic generanext 2 to 3 years. In the next 2 to 3 years marketing have to be taken into account. tion in a polymer waveguide" (to be 2-3 GHz switches would be needed.
published). Khanarian said that poled polymer films CONCLUSIONS had long range potential for low cost
Iqbal Ahmad is the director of the integrated circuits. Making large sheets The main consensus was that research Army Research Office (ARO) Far of poled polymer films for displays has in the area of NLO organic materials is East. He has a Ph.D. degree in physical a lot of potential. Shuto stated that important as these materials have chemistry from Imperial College, there were a large number of researchers considerable potential for future London, and is a Fellow of the Royal at NTT who were involved with NLO photonic requirements. Major areas Sociсty of Chemistry, London. Prior investigations, including SHG mate- for additional emphasis include syn- to his present position, Dr. Ahmad rials, optical phase conjugation, and thesis and preparation of single crys- was a program manager in the arca of optical computing. All had high hopes tals and thin films of novel organic materials science at ARO, Research for organic NLO materials. Yoshimura materials (using economically feasible Triangle Park, North Carolina. said that his company had three processes); improvement of their staresearchers working on optical switch- bility, hyperpolarizability, and nonlinear ing. Miyata said that most companies optical efficiency; minimization of were concentrating their research on optical absorption for increasing the second order nonlinear organic mate- frequency doubling efficiency, and better rials. The major difficulty of epitaxy theoretical models. had to be solved. Sasabe said that his
U.S.-INDIA WORKSHOP ON FRONTIERS
OF RESEARCH IN POLYMERS
Recent advances in polymer research as presented at the workshop are discussed.
by Iqbal Ahmad
Prasad of the scope of the workshopfor aerospace applications, and polymer
Dr. S.Z. Qasim, a member of the waste disposal. An International Conference on the Planning Commission of R&D in India, Dr. C.K.N. Patel of AT&T LaboraFrontiers of Polymer Research was held formally inaugurated the workshop. tories, in his keynote speech, gave an in Delhi in January 1991. The Army Qasim is Director of the Indian Institute overview of polymers for photonics Research Office Far East (AROFE) of Oceanography, Goa, and personally and electronics. He stated that the revwas one of the sponsors. Because of the led the Indian research team to enues from silicon-based electronics instability in the Gulf region, a number Antarctica last year. Mr. Dutt of the exceeded the oil revenues of the world of important contributors to the con- American Embassy in Delhi then and that silicon would continue to ference could not attend. In spite of described briefly the Indo-U.S. dominate the IC market for a long time. this there was considerable enthusi- collaborative program. He stated that He projected that by 1995 the feature asm and interest in the advances in currently there were almost 200 ongoing size of microelectronic ICs will be smaller polymer research discussed at the con- projects in India, in which the Office of than 0.3 micron, and the 64-MB DRAM ference. At the conclusion of the con- Naval Research (ONR), Naval Research will be commercialized by the end of ference it was the general consensus Laboratory (NRL), National Science the century. He explained the concept that contributors who could not come Foundation (NSF), Air Force Office of of “factory in bottle,” which is essento the conference be provided an oppor Scientific Research (AFOSR), and tially a new concept in which all opertunity to report their work at a work- Department of Energy (DOE) ations on the substrate from the start shop. So Dr. J.K. Nigam, Director of collaborate with Indian scientists. These to the finished state of the IC will be the Shriram Institute, Delhi, and Prof. projects are supported by the Indian conducted without taking the substrate P.N. Prasad, Director of the Photonic rupee fund to the tune of 200M rupees out of the controlled atmosphere at Laboratory, State University of New (about $8M). At this workshop a team any time. He described the future potenYork, Buffalo, organized the U.S.-India from the Air Force consisting of Dr. tial of silicon-based polymers, particuWorkshop on Frontiers of Research in Charles Lee (AFOSR), Dr. larly the polysylenes, which have a Polymers and Advanced Materials at Ed Helminiak [(Wright Research and sheetlike structure and can be used to Goa on 6-9 January 1991. It was cospon- Development Center (WRDC)], and provide films of controlled refractive sored by the Army Research Office Far COL C. Dymek (European Office of index and insulation properties. East (AROFE) and the Shriram Insti- Aerospace Research and Development The session on structural polymers tute. In all about 30 persons partici- (EOARD)] came to explore how was chaired by Dr. Helminiak, who is pated. The Proceedings will be pub- AFOSR could tap the scientific Chief of the Organic Polymers Branch lished. In the following, only highlights resources of India with the help of Indian at WRDC. In this session Dr. Bruno of the workshop are briefly described. funds.
Fanconi of the National Institute of
The workshop consisted of 10 ses- Standards and Technology (NIST), DISCUSSION OF
sions covering structural polymers, speaking on the issues and opportuniTHE WORKSHOP
conducting polymers, polymers for ties in high performance structural
integrated circuits (ICs), nonlinear polymers, highlighted the critical barAfter the welcoming remarks by optical polymer molecules, polymers riers in the area of intelligent processDr. Nigam and introduction by Prof.
ing. He stated that the critical barriers were the processing time, cost, and the that the problem areas were high cost radiation-induced polymerization techdurability of high performance poly- and low use temperature.
nique in which redox reactions can be mers. He reviewed some of the ongoing Prof. Alan MacDiarmid, the coin- induced in sensitive biosystems by work at NIST. This included modeling ventor of the first conducting polymer exposing them to a gamma ray source, of the reaction injection molding of series, polyanilines, gave an excellent without the danger of introducing any large composite components, which overview of the state of the art. He said contamination from the products of could be 30 to 40 feet long when used in that the research activity on conduct- reaction. Mittal described a number of advanced aircraft that are being designed ing polymers was increasing very rapidly applications in which this technique for flying at 2.5 mach at a height of For example, in 1991 the number of was used. One of the most interesting 30,000 feet. According to Fanconi, the patents granted was as high as 281 as was the development of a fast and cheap challenges in these technologies include compared with 106 in 1986. Also dur- technique for detecting bilirubin needed modeling of infiltration of heteroge- ing the last 12 months, Allied Signals to test for hepatitis. According to Mittal, neous preforms, three-dimensional (3D) has started manufacturing blends of it was almost like a litmus paper test flow, nonisothermal chemical reactions, polyanilines, which make them avail- and did not cost more than 50 pisa and nonlinear rheology. Process mon- able to researchers in larger quantities. (2 pennies per test kit). The test kits itoring is another area of importance. This should accelerate the progress of
This should accelerate the progress of have been distributed in a large numAromatic heterocyclic polymers were this potentially very fertile field. ber of Indian villages. Dr. Lal, Deputy the subject of the talk by Bob Evers of MacDiarmid described his latest results Director of the National Physical LaboWRDC. He described studies of the on the synthesis of high molecular weight ratory, Delhi, reviewed the various application of high performance poly- polyaniline. However, the data shown advanced analytical techniques availmers in advanced aircraft such as the did not indicate any dramatic improve. able at his laboratories for the characAV88, which is a modified version of ment in the electrical conductivity with terization of materials. the British Harrier. He said that while the increase in molecular weight. Prof. Photonics was the focus of the sesF-15 and F-18 aircraft contained 2% Epstein of Ohio State University, who sion chaired by Dr. Gallagher Daggitof and 10% nonmetallic materials, AV88 holds a dual position as Professor of the United Kingdom. Prof. Prasad gave had 27% organic polymers and their Chemistry and Professor of Physics and a review paper on “Molecular Matecomposites and predicted that future is at the same time Director of the rials and Structural Property Relationadvanced fighter aircraft may have as Materials Research Center, gave a stim- ship for Photonics." He stated that much as 40% nonmetallic materials. ulating paper on the electrical conduc- photonics is essentially light wave techHe briefly discussed the polybenzo- tance and magnetic susceptibility of nology, used for processing and storing thiozole (PBT) developed under Air polymers and discussed the synthesis of information. This includes optical Force contract and now picked up for and properties of deca-methyl- transmission, optical sensors, lasers, further development by DuPont. ferrocene, which he codiscovered with and photoactive components. The Another new polymer that is under one of his graduate students. The advantages of using photonics instead development at WRDC is benzocyclo- compound had a T of 4.8 K. New of electronics for data processing and butene, which shows thermal stability compounds such as v(CH) TCNE storage include faster speed, larger up to 500 to 600 °F. Blends of benzo- synthesized by his group have shown a volume of information processed, and cyclobutenes and bismaleimide also T of 35 K, which is very encouraging insensitivity to electromagnetic intershow considerable thermal stability. One advancement in the field of magnetic ference. For optical switching required of the newest and most promising poly- polymers. Prof. James Mark of the for optical processing of information, mers that is drawing considerable atten- University of Cincinnati presented one needs to use nonlinear optical effects tion is 6F-PBOs, which is a polybenzo- results of his study on high performance that allow the manipulation of light oxazole. Recently new synthesis pro- films from semiflexible polymers, and propagation by the application of the cesses of this polymer both by the Dr. Nigam reviewed the synthesis and electric field or laser pulse. In addition, Japanese and IBM have been reported. market trends of inorganic fibers used nonlinear optical effects give rise to Evers also presented some experimen- in the polymer industry either as fillers frequency conversion such as frequency tal data on molecular composites, such or reinforcements.
doubling for high density optical data as nylon plus 60% PBT. This compos- In the session chaired by Dr. Dymek storage and image analysis. Prasad ite has superior elasticity and strength, (EOARD), two interesting papers came discussed some of the work of his but low elongation. Commenting on from the Indian laboratories. Dr. Mittal laboratories on PBT and polyphenylene the thermoplastic polymers, he said from the Bhaba Atomic Research vinyl (PPV). The latter polymer film
Center, Bombay, described a new on stretching develops molecular orientation, which influences the third reported by him was that of Dr. India and the AFOSR programs. Such order nonlinear coefficient. Prasad's Venkatachalam, who has synthesized a
Venkatachalam, who has synthesized a proposals will be limited to only basic group has developed a sol gel process 3D pthalocyanine polymer. This poly- research areas, which would minimize for preparing silica polymer composite, mer is expected to have unique proper- problems related with intellectual which has a combination of superior ties, which are being investigated. Dr. property rights. In developing such low loss transmission character of glass Singh of the National Aeronautical proposals, if there is a need for an and high third order nonlinear coeffi- Laboratories, Bangalore, described the Indian scientist to visit an Air Force cient of the polymer. The sol gel tech- facilities of the institute for the fabrica- laboratory, it could be arranged through nique used is described in his paper tion and testing of organic polymer the EOARD Window on Science proreported in the Materials Research composites needed for aircraft struc
composites needed for aircraft struc- gram. I represented the position of ARO Society (MRS) Symposium Proceed- tures. Finally, in the concluding talk, and promised to explore with ARO ings Volume 175. While MacDiarmid Dr. Dhabolkar of the Shriram Institute participation in a similar manner in and others discussed polymers in which gave an interesting exposé of the sub- areas of research that are relevant to the electrical conductivity depends on ject of polymer waste disposal. He stated the research and development (R&D) the presence of delocalized pi elec- that unlike developed nations, there programs of the Army. Dr. Lee also trons, Dr. Höchstrasse of the Univer- was no major polymer waste in India. offered to coordinate with ARO as the sity of Pennsylvania described the In fact, keeping in mind the low living joint program evolved and refer promechanism of conduction of poly-di- standards of India, some of the waste posals (Indo-AFOSR) to ARO for hexyl-silane in which the conductivity products such as old tires, which are information, cosponsorship, or ARO is due to the delocalized sigma bonds disposed of by incineration in devel- show of interest. and the presence of rigid segments. oped countries, can be used in India in Dr. MacDiarmid offered suggestions Prof. Larry Dalton of the University of many ways. For example, they are used in which Indian scientists can initiate Southern California, Los Angeles, gave in village carts and then as shoes for the new projects. The suggestions included an excellent paper on the photo-induced villagers. He pleaded that developed synthesis of derivatives of known micropatterning in organic polymers. nations must keep in mind the needs of advanced conducting polymers and study The major message of his talk was that less developed nations when they embark of mechanisms and properties. Dr. through photo-induced cross linking on large waste disposal programs. In Prasad suggested chemical synthesis of certain polymers, such as azobenzenes, the case of polymer waste disposal, their nonoptical organic materials and the show as good or better nonlinear optic approach may not be applicable to third study of their property structure relacal behavior than the inorganic non- world countries.
tionship. Some of the characterization linear optical materials such as lithium
may need sophisticated equipment, niobate. This is an exciting result for CONCLUSIONS
which may not be available in India. researchers engaged in developing
The collaborator in the United States nonlinear optical organic polymers. In the concluding panel discussion, would work in that area.
Dr. Krishnamurthy of the Vikrim which was chaired by Dr. Charles Lee On the whole, the attendees of the Sarabhai Space Center, Trivandarum, of AFOSR, the major topic discussed workshop, particularly the Indian scidescribed some of the laboratory facil- was the opportunities for U.S.-India entists, were very enthusiastic about ities at his center and stated that most collaborative research, in which the the collaborative program. From the of the polymers and composites used in rupee fund could be used effectively. triservice point of view, it is a window the two-stage launch rocket for placing Lee stated that AFOSR would like to of opportunity, as with little effort and Indian satellites in space were manu- participate in the collaborative pro- almost no dollar investment highly factured by the center, either in their grams with Indian scientists, as ONR qualified scientists in India can be made own laboratories or on contract with and NSF are doing. Such projects should available to work on selected Departthe Indian industry. He stated that his be mutually beneficial. He encouraged ment of Defense R&D programs. Indian laboratory had excellent capabilities in the Indian scientists to contact AFOSR, scientists are very good at theoretical organic synthesis. Although they were indicating their expertise and ideas for studies because of the very high stannot doing too much in conducting collaboration. AFOSR would get them dards of education in mathematics. They polymers, as in the context of the Indian in touch with the right persons in their are also very well versed in chemical environment, these materials are not research laboratories. They could then synthesis, computer software, and thein demand; however, some work done jointly develop a research proposal, oretical physics. These resources can in basic synthetic chemistry was rele- which would be evaluated for technical be effectively utilized to the mutual vant. One of the outstanding efforts merit and relevance to the needs of benefit of the two countries.