Poly- imides properties

ACS Division of Polymer Chemistry Workshop on The Chemistry and Properties of Poly imides, Proc., (ed.) Hergenrother, P. M. Reno, Nevada, June 1985 and also July 1987... 

Mitsui Chemicals is launching a new grade of carbon nanotube reinforced thermoplastic poly-imide, Aurum CNT, with supplementary specific properties such as dust reduction and antistatic behaviour. Targeted applications are, for example, processing jigs for semiconductor or hard disk manufacturing, and parts for hard disk drives. 

Fluorinated poly(imide-ether-amide)s are readily soluble in organic solvents like dimethylformamide (DMF), N-methylpyrrolidone (NMP), pyridine or tetrahydrofu-ran (THF) and give flexible films by casting of such solutions. These polymers exhibit decomposition temperatures above 360°C, and glass transition temperatures in the 221-246° C range. The polymer films have a low dielectric constant and tough mechanical properties. 

Of all the hydrocarbon-based PEMs, this group most likely has the largest variety of different systems. This is probably due to the wealth of prior knowledge of the nonsulfonated analogues that have been developed over the last several decades as well as the general expectation of higher thermal stability, better mechanical properties, and increased oxidative stability over polystyrene-based systems. Within the context of this section, polyarylenes are systems in which an aryl or heteroaryl ring is part of the main chain of the polymer. This section will, therefore, include polymers such as sulfonated poly (ether ether ketone) and sulfonated poly(imides) but will not include systems such as sulfonated polystyrene, which will be covered in Section 3.3.I.3. 

Postsulfonation of polymers to form PEMs can lead to undesirable side reactions and may be hard to control on a repeatable basis. Synthesis of sulfonated macromolecules for use in PEMs by the direct reaction of sulfonated comonomers has gained attention as a rigorous method of controlling the chemical structure, acid content, and even molecular weight of these materials. While more challenging synthetically than postsulfonation, the control of the chemical nature of the polymer afforded by direct copolymerization of sulfonated monomers and the repeatability of the reactions allows researchers to gain a more systematic understanding of these materials properties. Sulfonated poly(arylene ether)s, sulfonated poly-(imide)s, and sulfonated poly(styrene) derivatives have been the most prevalent of the directly copolymerized materials. 

Sulfonated poly(arylene ether)s have shown promise for durability in fuel cell systems, while poly-(styrene)- and poly(imide)-based systems serve as model systems for studying structure-relationship properties in PEMs because their questionable oxidative or hydrolytic stability limits their potential application in real fuel cell systems. Sulfonated high performance polymer backbones, such as poly(phe-nylquinoxaline), poly(phthalazinone ether ketone)s, polybenzimidazole, and other aromatic or heteroaromatic systems, have many of the advantages of poly-(imides) and poly(arylene ether sulfone)s and may offer another route to advanced PEMs. These high performance backbones would increase the hydrated Tg of PEMs while not being as hydrolytically sensitive as poly(imides). The synthetic schemes for these more exotic macromolecules are not as well-known, but the interest in novel PEMs will surely spur developments in this area. 

Throughout this chapter the chemical concepts employed to synthesize and cure addition poly(imides) have been discussed and their use as matrix resins for fiber composites has frequently been mentioned. The most important property of the imide backbone structure is the inherent thermal stability. The target of achieving the temperature performance of linear poly(imide) has not been reached, because of the aliphatic nature of the reactive endgroups, and because of the low molecular weight of the imide backbone required for processing. Future developments of addition polyimides will, as in the past, focus on the requirement of high thermal and thermal oxidative stability of the crosslinked... 

A great deal of literature attention has been devoted to polymers in this section as thermally stable polymers (B-80MI11101). While some very elegant syntheses have been conducted, the resulting polymers have been, for the most part, quite intractable materials not conducive to extensive screening for a variety of applications. Thus, aside from their bulk thermal performance, little else besides the conditions of synthesis is known about most of the polymers shown. Three notable exceptions about which considerable characterization and product information are available are poly(imides), poly(benzimidazoles) and poly(quinoxalines), and a short discussion is included concerning properties and applications of these polymers. 

The latter property is somewhat of a mixed blessing, however. Poly(imides) are only soluble, for the most part, in extreme solvents such as concentrated sulfuric acid, fuming nitric acid and m-cresol. This lack of solubility in common solvents and their high melt temperatures render poly(imides) virtually intractable. For this reason, processing of the poly(imides) directly is often avoided by utilizing the polyfamic acid) precursor (Scheme 54). The more processable poly(amic acid) can be cast from solution, for example, and the poly(imide) may be generated in the desired configuration by thermolysis at 300 °C. 

US 5,028,681 (American) 1991 Novel poly(imide siloxane) block copolymers and process for their preparation General Electric EN Peters Injection moldable block copolymers with high IV and excellent chemical/physical properties. Blends useful for impact modification Novel siloxane-imide block copolymers and a process for their preparation are covered. The method involves reacting a hydroxy-terminated polyimide oligomer with a siloxane oligomer with dimethylamino, acetyl or chlorine end-groups... 

Bisimide 301, derived from compound 288, was used to ptepare an alternating (as opposed to block) poly(estet-imide) by teaction with bisphenol A. Such polymets have better solubility properties than pure poly(imide)s <2000PSA1090>. 

Thompson, D.S., Thompson, D.W., and Southward, R.E. (2002) Oxo-metal-polyimide nanocomposites. 2 enhancement of thermal mechanical and chemical properties in soluble hexafluoroisopropyUdene-based poly-imides via the in situ formation of oxo-lanthanide(III)-polyimide nanocomposites. Chemistry of Materials, 14,... 

The synthesis and properties of poly(imide-siloxane) polymers and copolymers based on 5,5 bis(lyly3,3-tetramethyl-l,3-disiloxane-diyl)norbornane dicarboxylic anhydride are described. High-molec-ular-weight thermoplastics and elastoplastics were prepared readily in solution from aromatic diamines, organic dianhydrides, and this unique anhydride-terminated siloxane. The thermal and mechanical properties of a variety of copolymer compositions are described. Average siloxane block length and overall siloxane content had the greatest effect on these properties. 

In recent years, RO membrane research has proceeded in two diredrions. First, there has been a continuing search for new polymeric membrane materials. Some of the materials with interesting properties that could be cited include other cellulose esters polybenzimidazolea polybenzimidazolone (PBIL), poly-imides and new aromatic polyamides... 

Poly(imide)s as a class of polymer exhibit a range of properties, such as high Tg, excellent thermal stability, high chemical resistance, low dielectric constant and ease of fabrication, which have lead to important uses in the semiconductor and advance composite industries. In addition, the high aromatic content of many of these polymers and consequent high stability to ionizing radiation, leads to usage of poly(imide) films and composites in the nuclear and aerospace industries. 

Many poly(imide)s are insoluble in their processed form, either because of interchain charge-transfer interactions, or because of the presence of crosslinks in cured poly(imide) resins. The range of analytical techniques available to characterize processed poly(imide)s is therefore limited. NMR spectroscopy, and in particular solid-state NMR [1-3], has an important role to play in the determination of structure, conformation, morphology and molecular motion in poly(imide) materials. The aim of this chapter is first, to briefly summarize the various classes of poly(imide)s, second, to review the current literature on NMR of these materials and finally, to hopefully indicate where NMR spectroscopy will make further additions to the knowledge of the properties of poly(imide)s. 

There is much interest in the formation of blends of poly(imide)s with other polymers, so as to improve properties such as toughness and processability [14-19, 58, 59]. The subject of measurement of interactions and miscibility of blends by NMR spectroscopy has been discussed by Takagoshi and Asano in Chapter 10 of this book, and will not be referred to in detail here. The use of NMR to study miscibility in blends containing poly(imide)s is somewhat restricted because most poly(imide)s contain a high proportion of aromatic groups, and consequently form blends with other highly aromatic polymers. The CPMAS spectra, which as discussed above are broad and... 

In the previous chapters we have described the ablation properties of polymers designed for ablation and of reference polymers, i.e., mainly poly-imide. 

---