Pyrrolidones, from polyamides

Anionic polymerization of 67 by the activated monomer mechanism should occur with the selective cleavage of the CO—NH bond of the monomer to give a polyamide composed of kinetically controlled cis units (68c). However, the cis units isomerize to the thermodynamically more stable trans units (68t) through the proton abstraction from the methine group adjacent to the carbonyl group. This was ascertained by the isomerization experiment in which a polymer consisting of 92% cis unit and 8% trans unit was converted to one containing 40% cis unit and 60% trans unit when heated in dimethyl sulfoxide at 80 °C for 6 hours in the presence of 15 mol% potassium pyrrolidonate. 

Experimental films were prepared from polyamic acid or polyamide-imide solutions in 1-methyl-2-pyrrolidone (NMP) solvent by casting on soda-lime glass plates and curing in a forced air oven for one hour each at 80°C, 200°C, and 300°C. The resulting films were 25-50 microns thick. 

The results obtained here confirm their findings, and extend them by showing that even a small percent of N-methylation is sufficient to change the hydrodynamic properties of the para-linked aromatic polyamide molecule. The agreement between the molecular weights measured for polymer 7 (50% N-methyl substitutive) in 96% sulfuric acid and the N-methyl pyrrolidone with 5% LiCl and 1% water implies that this polymer forms a molecularly disperse solution in the latter solvent. This observation differs significantly from the report by Tsvetkov et al. (6) and Koton and Nozova (5) that the fully methylated polymer only formed molecularly disperse solutions in sulfuric acid. 

The fiber may be spun from a solution of the polymer in dimethylformamide containing lithium chloride. In 1973, Du Pont commenced production of another aromatic polyamide fiber, a poly(p-phenylene terephthalamide) marketed as Kevlar. It is produced by the reaction of p-phenylenediamine with terephthaloyl chloride in a mixture of hexametylphosphoramide and N-methyl pyrrolidone (2 1) at -10 C. 

Methyl-2-pyrrolidinone (NMP) n, (CH3) NCH2CH2CH2C = O. A solvent with a low order of inhalation toxicity, good thermal and chemical stability, and a high flash point. It is capable of dissolving resistant resins such as polyamide-imides, epoxies, urethanes, nylon, and PVC. It is a solvent of choice for spinning PVC fibers from solution. Previously known an N-methyl-2-pyrrolidone. 

In a similar way, the synthesis of aromatic polyamides from aromatic diamines m-phenylenediamine, p-phenylenediamine, bis(4-aminophenyl)methane, and bis(4-aminophenyl)ether and dicarboxylic acids such as isophthalic and tereph-thalic acid was performed in a household microwave oven [72]. The polycondensation was carried out in an JV-methyl-2-pyrrolidone (NMP) solution in the presence of triphenyl phosphite (TPP), pyridine, and lithium chloride as condensing agents to produce a series of polyamides with moderate inherent viscosities of 0.21-0.92 dL/g within 30-50 s. However, no marked differences in molecular weight distribution and inherent viscosities between the polyamides produced by conventional (60 s, 220 °C) and microwave methods were found [72]. 

Block copolymer systems have aroused interest with reviews of the synthesis of nylon elastomers, thermoplastic polyether-polyamide elastomers, and thermoplastic cross-linked polyamides of 3,3 -bis(hydroxymelhyl) glutaric add. Block copolymers were also reported from poly(/n-phenylene isophthalamidc) and poly(ethylene oxide) or poly(dimethylsiloxane). The polycondensation of oco -dicarboxylic-poly(amide 11) and x -dihydroxy-polyoxyethylene has also been studied and rate constants and activation energies evaluated for the process. The polycondensation of axo -diacid and e9o> -diester-poly(amide 11) oligomers with cuco -dihydroxy-polyether oligomers has similarly been reported. Lactam Rli -opening Polymerization Routes.—The effects of ring size, substitution and the presence of heteroatoms on the polymerizability of lactams has been the subject of reviews. - In the field of lactam polymerization, two systems have evoked major interest, namely caprolactam and 2-pyrrolidone. Studies on caprolactam have reported the effect of water on the mechanism of polymerization and polymerization rate, where it was found that the process was... 

On the basis of the results obtained so far using the three methods mentioned above, a relevant conclusion can be drawn the accurate temperature control (S 170 ° C) permits to mn polymerizations of CL in quasi-isothermal conditions and very efficiently contribute to the minimization of side reactions, the other relevant factor in this respect being the use of very fast activator/initiator pairs. Only the simultaneous effect of both factors, that is, temperature control and very fast catalytic systems, allows to reach both optimum process conditions and excellent polymer properties. The use of slow activators, such as N-acetyl-CL, on the contrary, strongly limits possible advantages of the method. Moreover, it should be taken into account that in general, solution polymerizations (methods 1 and 3) ate characterized by lower reaction rates as compared to suspension processes (method 2). On the other hand, these latter methods have to face more difficult and expensive purification procedures of the polyamide from the reaction mixture. The only other lactam-based polyamide synthesized in powder form in laboratory by a suspension process is poly(2-pyrrolidone). A description of its synthesis is given in Section 4.14.11.1. 

Imai (1996a) developed a new facile method for the rapid synthesis of aliphatic polyamides and polyimides from polycondensation of ra-antino acids and nylon salts. The polymerization reactions were carried out in domestic nticrowave oven in the presence of a small amount of a polar organic medium. Suitable organic media for the polyamide synthesis are tetramethylenesulfone (TMS) amide-type solvents such as N-cyclohexyl-2-pyrrolidone (CHP), 1, 3-dimethyl-2-imidazoUdone (DMI), phenolic solvents like m-cresol and o-chlorophenol, etc. and for the polyimide synthesis amide-type solvents such as N-methyl-2-pyrrolidone (NMP), CHP and DMI. In polyamide synthesis, the polycondensation was almost complete within 5 min, producing a series of polyamides with inherent viscosities aroimd 0.5 dL/g, and the polyimides having the viscosity values above 0.5 dL/g were obtained within 2 min. 

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