Polyamides, substituted

Amidation. Heating of the diammonium salt or reaction of the dimethyl ester with concentrated ammonium hydroxide gives adipamide [628-94-4] mp 228°C, which is relatively insoluble in cold water. Substituted amides are readily formed when amines are used. The most industrially significant reaction of adipic acid is its reaction with diamines, specifically 1,6-hexanediamine. A water-soluble polymeric salt is formed initially upon mixing solutions of the two materials then hea ting with removal of water produces the polyamide, nylon-6,6. This reaction has been studied extensively, and the hterature contains hundreds of references to it and to polyamide product properties (31). 

PyraZolines. l,3-Diphenyl-2-pyia2olines (7) (Table 2) aie obtainable from appiopiiately substituted phenyUiydiazines by the Knoii reaction with either P-chloro- or P-dimethylaminopropiophenones (30,31). They are employed for brightening synthetic fibers such as polyamides, cellulose acetates, and polyacrylonitriles. 

The hterature notes many other polyamide hoUow fibers, none of which have achieved significant commercial success. Included in this category are such polymers (some of which are cross-linked) as piperazinamides, hydrazine, substituted acrylamide, and modified and grafted nylons. 

Carboxyhc acids react with aryl isocyanates, at elevated temperatures to yield anhydrides. The anhydrides subsequently evolve carbon dioxide to yield amines at elevated temperatures (70—72). The aromatic amines are further converted into amides by reaction with excess anhydride. Ortho diacids, such as phthahc acid [88-99-3J, react with aryl isocyanates to yield the corresponding A/-aryl phthalimides (73). Reactions with carboxyhc acids are irreversible and commercially used to prepare polyamides and polyimides, two classes of high performance polymers for high temperature appHcations where chemical resistance is important. Base catalysis is recommended to reduce the formation of substituted urea by-products (74). 

Substituted amides (not of the alkanolamide variety) are sold to diverse low volume markets. They have some utility ki polymers such as polyethylene, ethylene-vinyl acetate copolymers, acryUc polymers, PVC, polyamides, and polyesters. They have been found effective as pharmaceutical processkig aids, defoamers (qv), antimicrobials, pesticides, kisect repellents, dispersion stabilizers, and corrosion inhibitors. 

Occasionally, water-soluble plastics are required. Poly(vinyl alcohol) is commonly the first to be considered but some cellulose ethers, polyethylene oxides, poly(vinyl pyrrolidone) and A-substituted polyamides are among many possible alternatives. 

Plastics, in the modem meaning, are synthetic materials capable of being molded. The Greek word plastikos means to form. Natural products, while plastic, are usually excluded. Resins may be natural or synthetic. The distinction between plastics and resins is arbitrary - many synthetic materials are both. Historically, the term resin was applied to synthetic substitutes for the natural product plastic was applied to compositions involving molding in their fabrication. Cuslomarily, the fiber industry is considered to be distinct from the plastics industry, although it uses the same ra v materials - polyamides (nylon), cellulose, and cellulose acetate. 

Hie reaction of a diamine with a diester under anhydrous conditions is reasonably rapid. However, a side reaction at high temperatures (>200°C) is N-substitution. Unfortunately, this N-substitution is particularly strong with methyl esters,28 37 65 and therefore, methyl esters such as dimediyl terephthalate or dimedryl isoph-thalate cannot be used for thermal polyamidations. Other esters, such as ethyl, butyl, and phenyl ester, do not seem to have this problem. 

Aliphatic hyperbranched polyesters, 56 Aliphatic isocyanate adducts, 202 Aliphatic isocyanates, 210, 225 Aliphatic polyamides, 138 Aliphatic polyesteramides, 56 Aliphatic polyesters, 18, 20, 29, 32, 87 degradable, 85 hyperbranched, 114-116 melting points of, 33, 36 structure and properties of, 40-44 syntheses of, 95-101 thermal degradation of, 38 unsubstituted and methyl-substituted, 36-38... 

Fig. 3.4 Polyamide-DNA binding motifs with equilibrium association constants K,). Hairpin amino-substitution at the a-position of the y-turn residue leads to enhanced binding affinity (10-fold) without loss of specificity, and with higher orientational selectivity and offers potential for further substitution. Cycle Cyclic polyamides show higher affinity than analogous hairpin molecules with the same number of cationic groups and eliminate all possibility of extended 1 1 binding. H-pin and U-pin compared to their non-linked analogs, H-pins and U-pins exhibit higher binding affinity. The black and open circles represent Im and Py rings, respectively diamonds repre-...

Recall that for a 2 1 polyamide DNA complex a subsef of pairing mles Im//9 or Py//9 pairs can substitute, in certain cases, for Im/Py or Py/Py pairs, respectively [36]. The incorporation of y9-alanine allows a broader set of sequences to be targeted with high affinity. However, the extra flexibility of polyamides containing internal y9-alanines allows both 2 1 and 1 1 hgand DNA stoichiometries in the mi-... 

Nielsen P.E., Egholm M., Berg R.H., Buchardt O. Sequence-selective recognition of DNA by strand displacement with a thymine-substituted polyamide. Science 1991, 254 1497-1500. 

Cherny D.Y., Belotserkovskii B.P., Frank-Kamenetskii M.D., Egholm M., Buchardt O., Berg R. H., Nielsen, P.E. DNA unwinding upon strand-displacement binding of a thymine-substituted polyamide to double-stranded DNA. Proc. Natl Acad. Sci. USA 1993 90 1667-1670... 

The PA-300 membrane was commercially developed by Riley and coworkers (15), and is similar to the NS-101 membrane in structure and fabrication method. The principal difference is the substitution of a polyetheramlne, the adduct of polyepichlorohydrin with 1,2-ethanediamine, in place of polyethylenlmine. Use of the polyetheramlne was significant improvement in that considerably higher membrane fluxes were possible at salt rejections equivalent to the NS-lOO membrane system. The actual barrier layer in the PA-300 membrane is a polyamide formed by Interfaclal reaction of Isophthaloyl chloride with the polyetheramlne. 

The tensile strength (how much pressure can be applied on the ends of a fiber before it breaks) of polymers is very dependent on the molecular weight and, although nylon 6,6 was made ten years earlier, the technical production problem of obtaining good molecular weight had to be overeome before it was used as a substitute for silk. Another example of a common polyamide is nylon 6,10, used as bristles in brushes. 

A-Carboxy-a-amino acid anhydrides, also referred to as 4-substituted oxazolidine-2,5-diones, Leuchs s anhydrides, or N-carboxyanhydrides (NCA), are polymerized by bases and transition metal complexes. Polymerization proceeds with simultaneous decarboxylation to produce a polyamide... 

The polyamide is a substituted nylon 2, that is, it is derived from an a-amino acid—the same type used in living organisms to produce polypeptides. NCA polymerizations have been used to synthesize polypeptides, both homopolymers and copolymers, that may be useful in biotechnology applications such as artificial tissues, drug delivery, and biosensors. 

PVC, polyamides, unsaturated crosslinked polyesters, ABS, and wood . Di- and tri-benzotriazole photostabilizers, such as (874) and (875) are synthesized from 2-nitro-benzenediazonium salts and an excess of 1,3-dihydroxybenzene or 1,3,5-trihydroxybenzene <85Mi 40i-0l>. The dibenzotriazole derivatives (874b and 875b) can be used as polymerizable acrylic UV absorbers <84PB237>. A few or/Ao-urethane and -trimethylsilane substituted 2-phenylbenzotriazoles (876 and 877) show similar photostabilization activity . Weather resistance of low-density polyethylene is improved by the addition of a benzotriazole-type photostabilizer <90M140i-04>. 

In order to develop a material with these properties, the well-documented thermal characteristics of the aromatic polyamides were combined with the sensitivity of a photolabile protecting group. In 1973, Amit and Patchornik reported that N-substituted-ortho-nitroanilides are light-sensitive and undergo a photoinduced rearrangement to produce the corresponding carboxylic acid in excellent yield. (4)... 

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