Amide groups polyamides/imides

In addition to the commercial aromatic polyamides described above many others have been prepared but these have not achieved commercial viability. There are, however, a number of other commercial polymers that contain amide groups such as the polyamide-imides. The latter materials are discussed in Section 18.14. 

In this paper we use dielectric measurements to calculate the polarizability of absorbed water in a series of aromatic polyimides and polyamide-imides. In the relatively non-polar polyimides, the absorbed water has a dipole moment close to that of free water (/i - 1.88 Debyes). This value drops to less than 0.4/x for polyamide-imides. The decrease may be attributed to hydrogen-bonded water in the very polar polyamide-imides. In addition, the "group" dipole moment for amide is calculated and found to be greater than the dipole moment of free water. 

The dipole moment of a selected functional group in the polymer can also be calculated using the Clausius-Mossotti equation. According to Van Krevelan, (15) the "effective polarizability" of a functional group in the polymer is calculated from the measured dielectric constant, the polymer density and the number of moles of that group in the polymer repeat unit. Using the data for the six polyamide-imides listed in Table I, the effective polarizability of the amide group can be determined from... 

For polyimides to be useful polymers, they must be processable, which means that they have to be meltable. Melt processability of polyimides can be improved by combining the basic imide structure with more flexible aromatic groups. This can be achieved by the use of diamines that can introduce flexible linkages like aromatic ethers and amides into the backbone. Polyamide-imides (5) are obtained by condensing trimellitio anhydrides and aromatic diamines, while polyetherimides (6) are produced by nitro displacement reaction involving bisphenol A, 4,4 -methylenedianiline, and 3-nitrophthalic anhydride. 

The thermoplastic variety of polyimides with enhanced melt processabihty is obtained by combining the basic imide stmcture with more flexible aromatic groups such as aromatic ethers or amides. Polyamide-imides are produced by condensing trimellitic anhydrides with aromatic diamines, while polyetherimides are made by the reaction between bisphenol A, 4,4 -methylene dianiline, and 3-nitrophthalic anhydride. 

Aramide fibers, according to a definition issued by the US Federal Trade Commission, consist of long-chained synthetic polyamides in which at least 85 % of the amide groups are bound directly to two aromatic rings. DIN specifies that such aramides can also contain imide groups. The worldwide production volume of aramide fibers is 40,000 t/a. 

A polyamide-imide (PAI) features alternating imide and amide substructure sequences, an example being a pyromellitimide and amide, with a general structure as indicated below, where A1 is an alkyl group. The IR spectrum of a polyamide-imide is similar to that of a polyimide, except that amide grouping provides an additional carbonyl stretching vibration at around 1670 cm ... 

The deep insight in the structure of the chains is often accompanied by little attention to their association in the solid state on the other hand, some authors are only concerned by the material without paying great attention to the macromolecule itself. However, some articles associate these two aspects, as did Purukawa et al. [117], who prepared polysiloxane-6-polyamide by solution polycondensation (xylene/NMP) of 3,3, 4,4 -diphenylsulfonetetracarboxylic dianhydride, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, and Qf,w-diammo-poly-siloxane (the synthesis belongs to the techniques listed in Section 2.3). The chains were analyzed by H, and Si NMR, as well as by infrared spectroscopy, whereas the spin-lattice relaxation time was measured by solid-state NMR. A kinetic study of the imidization was carried out in NMP solution it showed that the value of the activation energy is partly determined by the solvation of the amide groups and polyamic acids. 

Polyimides are a group of extremely strong polymers that are also highly heat and chemical resistant. These polymers contain the imide functionality. We have seen Uiat the amide functionality [—C(0)NH—] is present in synthetic polyamides like nylon-6,6 as well as in natural polyamides like proteins. The imide functional group is created when nitrogen is at-... 

Various approaches have been undertaken for reactive compatibilization of poly-amide/ABS alloys. Maleic anhydride can be grafted to the ABS. Styrene maleic anhydride (SMA) copolymers have been employed as compatibilizers for polyamide/ABS blends. SMA and SAN copolymers are miscible when the AN and maleic anhydride (MA) contents are equal. The impact strength of these blends has been found to be sensitive to the amount and composition of the SMA copolymer. Addition of SMA to SAN/polyamide blends was found to enhance the tensile and impact properties of these blends. Imidized acrylic polymers have been used as compatibilizers for nylon-6/ABS blends. Glycidyl methacrylate and methyl methacrylate (GMA/MMA) copolymers are used as compatibilizing agents. The epoxide functionality in GMA is capable of reaction with polyamide end groups. GMA/MMA copolymers can be shown to be miscible with SAN over the range of AN content of ABS. Styrene/GMA copolymers have been reported to be used as compatibilizers for polymer pairs such as... 

This technique has been applied to the quantitative determination of alkyl and aryl groups in polysiloxanes [123] and of imides in aromatic polyamides and poly(amide imides) [124]. 

METHOD 49 - DETERMINATION OF AMINO GROUPS IN AROMATIC POLYAMIDES, POLYIMIDES AND POLY(AMIDES-IMIDES). POTASSIUM HYDROXIDE FUSION-GAS CHROMATOGRAPHY. ... 

This alkali fusion gas chromatographic method determines down to 0.02% of amino groups in aromatic polyamides, polyimides and poly(amides-imides). 

Imide groups formed in polyamide 6 (polyhexanamide) hydrolyse faster than in polyamide 11 (polyundecanamide) and polyamide 12 (polydodecanamide). The role of water in the photo-oxidation of aliphatic amides is limited to a reaction with the imide groups [1321]. 

Quite recently,the anionic homopolymerization of a few substituted p-lactams and the copolymerization of some of the above pairs have been smdied in order to prepare polyamide 3-derived polypeptides displaying biological properties. The solution polymerization or copolymerization, initiated by li amide disubstituted with trrmethylsilyl groups and activated with 4-tert-butylbenzoyl chloride, does not have living character. From that study, some insights emerged into the reactivity of the above p-lactams in terms of their acidities, as well as electrophUidty of the imide end groups. 

Amino end groups of polyamides react with cyclic anhydrides to form the corresponding amide-acids, after which the reaction can continue forming stable imides, as depicted in Scheme 7. 

Determination of Amide and Imide Groups in Polyamides, Poiyimides, and Poiyamides/lmides... 

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