Polyetherimide structure

In 1982 General Electric introduced Ultem, a polyetherimide with the following structure ... 

Polyetherimides show no crystallinity as evidenced from calorimetry measurements. The heteroarylene like phenylquinoxaline [27], oxadiazole [30], and benzoxa-zole [56] activated polyethers show TgS from DSC thermograms, with no evidence of crystallization, indicating amorphous or glassy morphology. Furthermore, wide angle x-ray scattering measurements show no evidence of crystalline or liquid crystalline type morphologies, consistent with an amorphous structure. F polyether... 

Table 3.23 Performance examples of structural foam and dense polyetherimide...

The initial announcement for the commercial preparation of polyetherimides (PEIs) was made by General Electric in 1982 under the trade name Ultem. The final reaction involves the imidization of a diacid anhydride through reaction with a diamine, here w-phenylenedia-mine (structure 4.62). The ether portion of the polymer backbone results from the presence of ether linkages within the diacid anhydride. 

Polyetherimides (PEI) are polyimides containing sufficient ether as well as other flexibi-lizing structural units to impart melt processability by conventional techniques, such as injection molding and extrusion. The commercially available PEI (trade name Ultem) is the polymer synthesized by nucleophilic aromatic substitution between 1,3-bis(4-nitrophthalimido) benzene and the disodium salt of bisphenol A (Eq. 2-209) [Clagett, 1986]. This is the same reaction as that used to synthesize polyethersulfones and polyetherketones (Eq. 2-206) except that nitrite ion is displaced instead of halide. Polymerization is carried out at 80-130°C in a polar solvent (NMP, DMAC). It is also possible to synthesize the same polymer by using the diamine-dianhydride reaction. Everything being equal (cost and availability of pure reactants), the nucleophilic substitution reaction is probably the preferred route due to the more moderate reaction conditions. 

Using conventional spin-coating technology, phase-matching has been demonstrated with a 2 layer core structure made of DANS doped polycarbonate and polyetherimide over 7 mm of propagation [90]. 

Many computational studies of the permeation of small gas molecules through polymers have appeared, which were designed to analyze, on an atomic scale, diffusion mechanisms or to calculate the diffusion coefficient and the solubility parameters. Most of these studies have dealt with flexible polymer chains of relatively simple structure such as polyethylene, polypropylene, and poly-(isobutylene) [49,50,51,52,53], There are, however, a few reports on polymers consisting of stiff chains. For example, Mooney and MacElroy [54] studied the diffusion of small molecules in semicrystalline aromatic polymers and Cuthbert et al. [55] have calculated the Henry s law constant for a number of small molecules in polystyrene and studied the effect of box size on the calculated Henry s law constants. Most of these reports are limited to the calculation of solubility coefficients at a single temperature and in the zero-pressure limit. However, there are few reports on the calculation of solubilities at higher pressures, for example the reports by de Pablo et al. [56] on the calculation of solubilities of alkanes in polyethylene, by Abu-Shargh [53] on the calculation of solubility of propene in polypropylene, and by Lim et al. [47] on the sorption of methane and carbon dioxide in amorphous polyetherimide. In the former two cases, the authors have used Gibbs ensemble Monte Carlo method [41,57] to do the calculations, and in the latter case, the authors have used an equation-of-state method to describe the gas phase. 

Thermoplastic polyetherimide Ultem can be formulated with high temperature foaming agents such as 5-phenyldihydro-l,3,4-oxadiazinone to produce structural form products [99] by injection molding. PEI could be readily imbibed with various volatile organic compounds such as chlorinated hydrocarbons [100] and acetone [101]. 

Concurrent with these developments, the microwave vessel also evolved significantly. The vessels in microwave systems are relatively transparent to microwave radiation and inert to the reagents used. The materials in contact with the sample are usually of fluoropolymer, quartz or glass composition. Closed, pressurized vessels are frequently multi-layered, with a structural outer casing of a microwave-transparent polymer such as polyetherimide. This polymer is commonly used for its tensile strength, rigidity and ability to contain accumulated pressure. 

Polyetherimide has a chemical structure based on repeating aromatic imide and ether units. High performance strength characterisitics at elevated temperatures are provided by rigid imide units, while the ether linkages confer the chain flexibility necessary for good melt processing and flow. 

Some examples of wholly aromatic polyetherimides were synthesised by workers at Liverpool University [42] and shown to be liquid crystalline [43]. The structures are given in Table 8. 

To further investigate the question of polymer structure-permeability relationships, this study reports oxygen permeability measurements on a group of structurally varied bisphenol based polymers. In addition to representing commercially important classes of engineering thermoplastics, polycarbonates, polyarylates and polyetherimides can be easily prepared from a common set of... 

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