Poly , imidization

Capillary Tubes Figure 12.42 shows a cross section of a typical capillary tube. Most capillary tubes are made from fused silica coated with a 20-35-)J,m layer of poly-imide to give it mechanical strength. The inner diameter is typically 25-75 )J,m, which is smaller than that for a capillary GC column, with an outer diameter of 200-375 )J,m. 

Poly(imides) — see 3-Pyrroline-2,5-diones Poly(imidines) — see 3-Pyrrolin-2-ones Polyiodides... 

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... 

FIG. 3 Evolution with time, f, of contact angle, of NMP, with NMP containing 17.5 wt% of poly-imide and NMP containing 28 wt% of polyimide. 

McGrath, /. E, Dunson, A L., Hedrick,l L.i Synthesis and Characterization of Segmented Poly-imide-Polyorganosiloxane Copolymers. Vol. 140, pp. 61-106. 

The films were then thermally cycled at tOO, 200 and 300°C for an hour at each temperature in a forced air convection oven to complete the cyclization. The solution imidization procedure has been further described by Summers, et. al. (42,43). A representative structure for the poly(imide siloxane) copolymers is depicted in Figure 5. 

V.N. Reinhold and S.A. Carr, Desorption chemical ionization with poly-imide coated wires, Anal. Chem., 54 (1982) 499-503. 

This observation is further dramatized by some rather limited isothermal measurements on selected films (TABLE III). This data is typical of the metal ion filled BTDA + p,p -DABP poly-imides which we have examined. No changes in chemical functionality in the polyimide-metal film were apparent as judged by infrared spectral comparisons of polyimide alone and polyimide plus metal regardless of the metal employed. 

Soundproofing and thermal insulation of missiles, planes and helicopters cryogenic protection on satellites, piping insulation, protection for embarked equipment in poly-imide foams. 

PV limits are in a good range, similar to those of PES and a little inferior to those of poly-imide, especially at high temperature These results relate to a few grades only and cannot be generalized. 

Figure 4.120. Poly imides examples of linear dimensional variation (%) versus time (days)...

After cleaning by abrasion and with solvents, the polyimides can be stuck with a poly-imide, epoxy or acrylic resin adhesive whose thermal resistance is compatible with the operating conditions. Preliminary tests are essential. 

They are generally used in the form of prepregs 70% fibres/30% matrix of epoxy, poly-imide or phenolic resin. 

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. 

Shobha et al. employed a novel sulfonated diamine containing a phosphine oxide moiety in the synthesis of a five—membered ring sulfonated poly-imide. The synthesis is shown in Figure 24. 

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. 

The selective dense layer of hydrophilic membranes is made from different polymers with a high affinity for water. These polymers contain ions, oxygen functions like hydroxyl, ester, ether or carboxylic moieties, or nitrogen as imino or imi-do groups. Preferred hydropilic polymers are polyvinylalcohol (PVA) [32], poly-imides, cellulose acetate (CA) or natural polymers like chitosan [33] or alginates. Organophilic membranes usually consist of crosslinked silicones, mostly polydimethyl siloxane (PDMS) or polymethyl octyl siloxane (POMS). 

Besides in the liquid phase, some polyreactions are also performed in the solid state, for example, the polymerization of acrylamide or trioxane (see Example 3-24). The so-called post condensation, for example, in the case of polyesters (see Example 4-3), also proceeds in the solid phase. Finally, ring closure reactions on polymers with reactive heterocyclic rings in the main chain (e.g., poly-imides, see Example 4-20) are also performed in the solid state. 

Thus, N-pyrimidine phthalimide reacted with hexylamine at room temperature to form an amide-amide. The initial amide-amide formation proceeded more rapidly in chloroform as compared to dimethylsulfoxide (DM SO). However, the ring closure reaction to the imide was favored by the more polar, aprotic DMSO solvent, yielding the imide in nearly quantitative yield after 3 hours at 75 °C. The authors were able to utilize this synthetic approach to prepare well-defined segmented poly(imide-siloxane) block copolymers. It appears that transimidi-zation reactions are a viable approach to preparing polyimides, given that the final polyimide has a Tg sufficiently low to allow extended excursions above the Tg to facilitate reaction without thermal decomposition. Additionally, soluble polyimides can be readily prepared by this approach. Ultimately, high Tg, insoluble polyimides are still only accessable via traditional soluble precursor routes. 

Fig. 15. Dynamic mechanical thermal behavior of poly(imide-co-phenyl ether phenyl quinoxaline)...

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