Polyamides of Enhanced Solubility

Glass-fibre-filled grades of these toughened polymers are also available but these do not show the same improvement in toughness over normal glass-fibre-filled nylons. 

Since large tonnage production is desirable in order to minimise the cost of a polyamide and since the consumption of nylons as plastics materials remains rather small, it is important that any new materials introduced should also have a large outlet as a fibre. There are a number of polyamides in addition to those already mentioned that could well be very useful plastics materials but which would be uneconomical for all but a few applications if they were dependent on a limited outlet in the sphere of plastics. Both nylon 7 and nylon 9 are such examples but their availability as plastics is likely to occur only if they become established fibre-forming polymers. This in turn will depend on the economics of the telomerisation process and the ability to find outlets for the telomers produced other than those required for making the polyamides. 

Polyamides such as nylon 6, nylon 66, nylon 610, nylon 11 and nylon 12 exhibit properties which are largely due to their high molecular order and the high degree of interchain attraction which is a result of their ability to undergo hydrogen bonding. 

however, possible to produce polymers of radically different properties by the following modifications of the molecular structure. 

The techniques of A-alkylation may be effected by the use of A-alkylated or A2V -dialkylated diamines, or by the use of an w-A-alkylaminocarboxylic acid of type RjNHRCOOH. The polymers thus have repeating units of the general form. 

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Yet another type of polyamide nucleic acids analogs with a poly-L-lysine backbone (Fig. 20c, w = 4, z = 3) was described by Takemoto et al. (37). The ribose units in this analog mainly served the purpose of enhancing solubility of the polymers in water by the free hydroxy groups. For their preparation, 2 3 -0-isopropylidene-5 -0-glutaric acid succinimido nucleosides were coupled to prepolymerized L-lysine, a procedure not allowing sequence-specific introduction of nucleobases. 

Jin and Kim reported the synthesis of polyamides coordinated to chromium tricarbonyl moieties (11) by condensation of (ii -phenylenediamine)Cr(CO)3 (12) with various diacid chlorides (13) (Scheme 2)7 It was noted that this polymer exhibited enhanced solubility due to incorporation of pendent chromium tricarbonyl moieties along its backbone. The viscosities of these polymers were determined in concentrated sulfuric acid or A(2/-dimethylacetamide containing 5% LiCl. The inherent viscosities of these metallated polymers ranged from 0.72 to 1.53 dL/g, and were found to be higher flian those of their organic analogs. 

The solubility of these dyes is significantly enhanced by introduction of alkenyl [35], hydroxypropyl [36], or polyetheralkyl [37] moieties into the trialkylammonium group. The trialkylammonium group may also be a component of a heterocyclic ring [38], When the trialkylammonium residue contains an alkyl chain of more than 11 carbon atoms, the dyes become soluble in aliphatic and alicyclic hydrocarbons and can be used for the production of printing inks [39], With aromatic diamines as the diazo components, such as 4,4 -diaminodiphenyl sulfone, basic disazo dyes are obtained which are suitable for dyeing acid-modified polyamide materials [40],... 

Microwave-assisted polycondensation reactions in ILs have also allowed the enhanced synthesis of polyamides and polyurethanes the comparison between microwave synthesis conditions in ILs with conventional heating methods and conventional organic solvents has also been addressed [92, 93]. Pretreatment methods combining microwave irradiation and ILs for cellulose dissolution and modification have been also proposed [94, 95]. Microwave irradiation can enhance the solubility of cellulose in ILs and decrease the degree of polymerization of regenerated cellulose after IL dissolution, which can be beneficial for improving cellulose hydrolysis [95]. 

Depending on the modifications of poly-(p-phenylene terephthalamide) and analogous aromatic polyamides, it is possible to vary the solubility from concentrated sulfuric acid, to nonpolar aprotic solvents with inorganic salts, or to nonpolar aprotic solvents and to common organic colvents. In particular the incorporation of noncoplanar 2,2 -disubstitution has proven to remarkable enhance the solubility and lower the crystallinity. Gaudiana et al. [35] demonstrated that para-linked aromatic polyamides containing noncoplanar 2,2 -bis(trifluorome-thyl)biphenylene units are highly soluble in... 

The improvement in the solubility of the polyimides showed a similar tendency to that of the corresponding polyamides. For example, 2,5-di-f-butyl substituent in polymer backbone was too symmetrical for the solubility to be superior to that of /-butyl-substituted polymers From the solubility behaviors of the polyimides, therefore, it could be concluded that the incorporation of bulky pendant groups along the polymer chain gave the most effective enhancement in the solubility of polymers. (Fig. 2.8)... 

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