Nylon onium salts

SYNTHESIS OF ULTRAHIGH MOLECULAR WEIGHT NYLON 4 WITH ONIUM SALT AND CROWN ETHER-CONTAINING CATALYSTS... 

Scheme 1. Nylon 4 Synthesis with Onium Salts Catalyst Preparation...

The effect of onium salt anion on nylon 4 polymerization is shown in Table V. 

However, not every onium salt increases conversion and molecular weight in nylon 4 polymerization. It was found that a large number of onium salts act as inhibitors for the polymerization reaction. These results are summarized in Table VII. 

Since onium salts increase the rate and conversion in nylon 4 polymerization, one may think that they act as initiators for the reaction. However, the rate increase is not achieved at the expense of polymer molecular weight, indicating that onium salts do not function as initiators. Further evidence that onium salts are not initiators was obtained by determining the apparent number of chains, n, in selected nylon 4 polymerizations. These results are summarized in Table VIII. 

The data show that n is approximately the same for polymerizations carried out with py-K/C02 in the presence and absence of an onium salt. If TMAC were an initiator, a large increase in n would be expected. The fact that N-acetylpyrrolidone, a typical initiator, gives a much larger n is consistent with this analysis. It should be pointed out that for TMAC and N-acetylpyrrolidone pol3aneriza-tions the differ ce between the apparent number of chains would be even greater if Mn were used to calculate n because of the narrower molecular weight distribution of the onium salt prepared nylon 4. 

As it was shown, crown ethers increase significantly the rate and molecular weight in nylon 4 polymerization. In analogy to the onium salt polymerizations discussed above, it is postulated that these effects are caused by changes in the propagation rate of the polymerization. Thus, cation complexation by the crown ether breaks up the relatively tight py-K/C02 ion pair and produces a "free, more reactive pyrrolidone anion. This will propagate... 

SYNTHESIS OF ULTRAHIGH MOLECULAR WEIGHT NYLON 4 WITH ONIUM SALT AND CROWN ETHER-CONTAINING CATALYSTS. R. Bacskai, Chevron Research Company, 576 Standard Avenue, Richmond, California 94802. 

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