Synthesis and Study of New Polyamides with Side Oxadiazole Rings M. Bruma, 1 E. Hamciuc, 1 B. Schulz, 2 T. Kopnick, 3 Y. Kaminorz, 4 J. Robison 5 1 Institute of Macromolecular Chemistry, Aleea Ghica Voda 41A, Iasi, Romania 2 University of Potsdam, FZDOBS, Potsdam 14469, Germany 3 Institute of Thin Film Technology and Microsensors, Teltow, Germany 4 University of Potsdam, Institute of Physics, Potsdam 14415, Germany 5 Tyco Electronics Corporation, Menlo Park, California 94025 Received 19 April 2001; revised 5 April 2002; accepted Published online 19 November 2002 in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/app.11367 ABSTRACT: A series of six new aromatic polyamides with side oxadiazole rings has been synthesized by polycon- densation reaction of aromatic diamines containing pendent substituted oxadiazole groups with a silicon-containing di- acid chloride [namely, bis(p-chlorocarbonyl-phenylene)di- phenylsilane] or with a fluorine-containing diacid chloride [namely, hexafluoroisopropylidene-bis(p-benzoyl chloride)]. All polymers were easily soluble in amidic solvents, such as N-methylpyrrolidinone and dimethylformamide, and gave thin transparent films by casting such solutions. Very thin coatings were deposited onto silicon wafers and exhibited smooth, pinhole-free surfaces in atomic force microscopy investigations. The polymers showed high thermal stability, with decomposition temperature 400°C. Some of them did exhibit a glass transition, in the range 152–276°C, with a reasonable interval between glass transition and decompo- sition. Four of these polymers showed blue photolumines- cence, in the range 460 – 480 nm, which makes them prom- ising candidates for future use as high-performance materi- als in the construction of light-emitting devices. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 714 –721, 2003 Key words: thin films; luminescence; polyamides INTRODUCTION It is known that aromatic poly(1,3,4-oxadiazole)s ex- hibit high thermal resistance in an oxidative atmo- sphere, good hydrolytic stability, low dielectric con- stant, and tough mechanical properties. 1, 2 More re- cently, specific properties determined by the electronic structure of oxadiazole ring, especially its electron- withdrawing character, reinvigorated intensive research aimed at using such polymers as advanced materials in microelectronics, optoelectronics, and other indus- tries. Poly(arylene-oxadiazole)s can easily undergo chemical or electrochemical redox reactions, and the resulting conducting materials may be used in electro- chemical sensors or electroluminescent devices for full color displays, optical data processing, etc. 3–5 There is currently much research directed towards the discov- ery of new, blue-light-emitting polymers, with char- acteristics of high efficiency and high reliability. For such a purpose, polyoxadiazoles are of great interest because they can facilitate the injection and transport of electrons because of the electron-withdrawing char- acter of the 1,3,4-oxadiazole rings. 6, 7 But, aromatic polyoxadiazoles are rigid, rod-like molecules, are in- soluble in organic solvents, and do not have a glass transition (T g ), which makes their processing quite difficult. To make such polymers processable, various approaches have been undertaken to improve the sol- ubility and lower the T g ; for examples, by introducing flexible side groups on the aromatic rings 8 or bulky moieties, such as “cardo” groups, 9 in the main chain. Another way would be the incorporation of oxadia- zole rings as pendent groups on a polymer chain. 10, 11 In this latter case, to maintain the high thermal stabil- ity, the main chain itself has to be thermostable in nature. Therefore, we considered it of interest to make polymers in which the oxadiazole rings are attached as side groups to an aromatic polyamide backbone. But, highly thermostable fully aromatic polyamides are also known as insoluble materials and very diffi- cult to be processed. One method to improve solubil- ity and lower the T g of aromatic polyamides and of other aromatic polymers is the introduction of flexibi- lizing groups, such as diphenylsilane units, in the main chain. 12–14 Moreover, electrochemical studies have shown that when incorporated between two para-phenylene rings in the main chain, silicon atoms give a – conjugation and support the transport of electrons. 15 Also, the hexafluoroisopropylidene (6F) groups can serve as flexibilizing bridges for an aro- matic polymer backbone, and consequently a large class of 6F-containing polymers has been recently de- Correspondence to: M. Bruma (mbruma@icmpp.tuiasi.ro). Journal of Applied Polymer Science, Vol. 87, 714 –721 (2003) © 2002 Wiley Periodicals, Inc.