Polyimides chemistry

Grunze M, Unertl W N, Ganara]an S and French J 1988 Chemistry of adhesion at the polyimide-metal interface Mater. Res. Soc. Symp. Proc. 108 189... 

Polyimides (PI) were among the eadiest candidates in the field of thermally stable polymers. In addition to high temperature property retention, these materials also exhibit chemical resistance and relative ease of synthesis and use. This has led to numerous innovations in the chemistry of synthesis and cure mechanisms, stmcture variations, and ultimately products and appHcations. Polyimides (qv) are available as films, fibers, enamels or varnishes, adhesives, matrix resins for composites, and mol ding powders. They are used in numerous commercial and military aircraft as stmctural composites, eg, over a ton of polyimide film is presently used on the NASA shuttle orbiter. Work continues on these materials, including the more recent electronic apphcations. 

Resins for advanced composites can be classified according to their chemistry typical resins are polyaryletherketones, polysulfides, polysulfones, and a very broad class of polyimides containing one or more additional functional groups (Table 2) (see also Engineering plastics). 

In addition they may contain ether, amide, carbonyl, sulfone, or other functional groups. References 28 and 29 provide excellent reviews of polyimide chemistry. 

The polyimide shown is a tme thermosetting resin, but the general reaction procedure, coupling the dianhydride with the diamine, is extremely important throughout polyimide chemistry. The intermediate polyamic acid polymers form the basis for many of the polyimide resins used in advanced composites. 

D. Wilson, H. D. Stenzenberger, and P. M. Hergenrother, Polyimides—Chemistry and Applications, Blackie and Sons Ltd., Glasgow, 1990. 

Photosensitive functions are in many cases also heat sensitive, so the preparation of photosensitive polyimides needs smooth conditions for the condensations and imidization reactions. Some chemical reactants, which can be used for polyamide preparation, have been patented for the synthesis of polyimides and polyimide precursors. For example, chemical imidization takes place at room temperature by using phosphonic derivative of a thiabenzothiazoline.102 A mixture of N -hydroxybenzotriazole and dicyclohexylcarbodiimide allows the room temperature condensation of diacid di(photosensitive) ester with a diamine.103 Dimethyl-2-chloro-imidazolinium chloride (Fig. 5.25) has been patented for the cyclization of a maleamic acid in toluene at 90°C.104 The chemistry of imidazolide has been recently investigated for the synthesis of polyimide precursor.105 As shown in Fig. 5.26, a secondary amine reacts with a dianhydride giving meta- and para-diamide diacid. The carbonyldiimidazole... 

Figure 5.26 Synthesis of rodlike polyimide using imidazolide chemistry.

Chemistry (Continued) polyimide, 287-300 polyurethane, 222-236, 546 transition metal coupling, 483-490 Chiral conjugated polymers, 479-480 Chlorinated solvents, 91 Chlorofluorocarbons (CFCs), 201, 205 Chloroformate endgroups, 87 Chloromethylation, 354 Church, A. Cameron, 431 Circular dichroism, 490 Classical catalysts, 433 Clean Air Act of 1990, 201, 205 Clearcoat, 240... 

Imide aryl ether ketone segmented block copolymers, 360 Imide chemistry, 292-295 Imide cyclization, 301 Imide exchange, polyimide syntheses by, 268... 

Recent work has focused on a variety of thermoplastic elastomers and modified thermoplastic polyimides based on the aminopropyl end functionality present in suitably equilibrated polydimethylsiloxanes. Characteristic of these are the urea linked materials described in references 22-25. The chemistry is summarized in Scheme 7. A characteristic stress-strain curve and dynamic mechanical behavior for the urea linked systems in provided in Figures 3 and 4. It was of interest to note that the ultimate properties of the soluble, processible, urea linked copolymers were equivalent to some of the best silica reinforced, chemically crosslinked, silicone rubber... 

Manufacture of Printed Wiring Boards. Printed wiring boards, or printed circuit boards, are usually thin flat panels than contain one or multiple layers of thin copper patterns that interconnect the various electronic components (e.g. integrated circuit chips, connectors, resistors) that are attached to the boards. These panels are present in almost every consumer electronic product and automobile sold today. The various photopolymer products used to manufacture the printed wiring boards include film resists, electroless plating resists (23), liquid resists, electrodeposited resists (24), solder masks (25), laser exposed photoresists (26), flexible photoimageable permanent coatings (27) and polyimide interlayer insulator films (28). Another new use of photopolymer chemistry is the selective formation of conductive patterns in polymers (29). 

Fullerene modified polyimide derived from 3,30,4,40-benzophenonetetracarboxylic acid and 3,30-diaminobenzophenone for casted items and its use in tribology, Russian Journal Applied Chemistry, vol. 76, pp. 1156-1163, 2003. 

I, H. Tseng, Y. F. Liao, J. C. Chiang, M. H. Tsai, Transparent polyimide/graphene oxide nanocomposite with improved moisture barrier property., Materials Chemistry and Physics, vol. 136, pp. 247-253, 2012. 

The thermal polymerization of reactive polyimide oligomers is a critical part of a number of currently important polymers. Both the system in which we are interested, PMR-15, and others like it (LARC-13, HR-600), are useful high temperature resins. They also share the feature that, while the basic structure and chemistry of their imide portions is well defined, the mode of reaction and ultimately the structures that result from their thermally activated end-groups is not clear. Since an understanding of this thermal cure would be an important step towards the improvement of both the cure process and the properties of such systems, we have approached our study of PMR-15 with a focus only on this higher temperature thermal curing process. To this end, we have used small molecule model compounds with pre-formed imide moieties and have concentrated on the chemistry of the norbornenyl end-cap (1). 

Solid state NMR has been used to study polymers of various classes over the past several years. In particular, the technique has been used to study curing reactions in epoxies (12). polyimides (1), and acetylenic terminated sulfones (13). The ability to observe the evolution of the carbons of the reacting species has been clearly shown to provide valuable information which has been difficult or impossible to obtain with other techniques. The use of 13C solid state NMR techniques is essential for the understanding of curing reactions in high temperature polymers in order to be able to correlate the reaction chemistry with the structural and resulting physical properties. 

Miyatake, K., Asano, N. and Watanabe, M. 2003. Synthesis and properties of novel sulfonated polyimides containing 1,5-naphthylene moieties. Journal of Polymer Science Part A Polymer Chemistry 41 3901-3907. 

Zhou, W, Watari, T., Kita, H. and Okamoto, K. 2002. Gas permeation properties of flexible pyrolytic membranes from sulfonated polyimides. Chemistry Letters 5 534-535. 

Einsla, B. R., Hong, Y. T., Kim, Y. S., Wang, F., Gunduz, N. and McGrath, J. E. 2004. Sulfonated naphthalene dianhydride based polyimide copolymers for proton-exchange-membrane fuel cells. 1. Monomer and copolymer synthesis. Journal of Polymer Science Part A Polymer Chemistry 42 862-874. 

Brian Einsla was born in Wilkes-Barre, PA, in 1978. He earned his Bachelor of Science degree in 2000 in Chemistry at Virginia Polytechnic Institute and State University. He is currently a fourth-year Ph.D. candidate in the Macromolecular Science and Engineering program at VPI SU. His research interests have centered around sulfonated heterocyclic copolymers for fuel cell applications, including polyimides, polybenzoxazoles, and polybenzimidazoles. 

Hedrick JL, Labadie JW, Russel TP (1989) In Feger C, Khajastech MM, McGrath JE (eds) Polyimides Materials, chemistry and characterization. Elsevier Science Publishers, Amsterdam, p 61... 

The solution behavior of poly(amic acids) was until recently, probably the least understood aspect of the soluble polyimide precursor. However, the advent of sophisticated laser light scattering and size exclusion chromatography instrumentation has allowed elucidation of the solution behavior of poly(amic adds). In the early days of polyimide chemistry, when most molecular weight characterization was based on viscosity determinations, a decrease in viscosity was associated with molecular weight degradation [15, 28, 29]. Upon combination of the two monomers an increase in the viscosity to the stoichiometric equivalence point is observed, followed by a decrease in the solution viscosity as a... 

The preparation of imides from reaction of isocyanates with anhydrides dates back to the early days of organic chemistry [96]. With the advent of polyimide chemistry in the early 1960s, this chemistry was soon explored for the synthesis of polyimides. However, in contrast to the preparation of polyimides via thejr poly(amic acid) intermediate, the reaction of aromatic dianhydrides with aromatic diisocyanates is much less understood. The reaction of aromatic dianhydrides with aliphatic or aromatic diisocyanates is believed to form a cyclic seven-membered intermediate which then splits out C02 to form the polyimide [97], see Scheme 27. The addition of water, which has been reported to accelerate the anydride/isocyanate reaction, can result in several transformations of either the anhydride or the isocyanate reagent, see Scheme 28... 

The preparation of N-alkyl imides by exchange reaction of an imide with an alkyl amine was documented [104] well before the application of this chemistry to the preparation of polyimides [105], see Scheme 30. Although no experimental details are provided, the initial reaction of pyromellitimide with p,p-methylene dianiline in NMP takes place at reflux temperatures to apparently yield a poly(amic amide). Subsequent heating of this intermediate at elevated temperatures ( 300 °C) provides the desired polyimide with evolution of ammonia. The final polyimide is quoted to be thermally and chemically stable, however, no mechanical properties are given. 

Complementary to the synthetic aspects of polyimide chemistry, a wealth of information addressing structure-property relationships of a wide spectrum of polyimides can be found in the literature. Information of this nature can be readily obtained from the literature along with potential application related data [11,131-136]. 

Model polyamicdialkylamides were prepared by the reaction of the secondary amines (XX) and (XXI) with the polyisoimide (XVII) in DMAC at room temperature. Unfortunately, the resultant polyamicdialkylamides only exhibited limited softening behavior for processing into bulk specimens. The inability to provide molded specimens prevented the validation of the In Situ Molecular Composite concept. Research is currently being carried out at a number of academic and industrial institutions on new thermoset chemistry, polyamices-ters, and extended chain polyimides. 

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