Anionic polymerization of 2‐pyrrolidone in the presence of cryptate

Abstract

Two principal advantages can be expected from the use of macroheterobicyclic compounds in the anionic polymerization: first, solubilization of the alkaline catalysts which are otherwise difficult to dissolve in organic solvents of weak dielectric constants, and second, enhancement of their catalytic activity'! The anionic polymerization of 2-pyrrolidone normally proceeds in the absence of solvent and the catalyst is at least macroscopically soluble in the monomer. Therefore, the first advantage above does not count in this case, but it is interesting to know to what extent the second point influences the reaction.We studied the anionic polymerization of 2-pyrrolidone catalyzed by the potassium salt of this lactam, potassium 2-pyrrolidon-l-ide, in the presence or the absence of the macroheterobicyclic compound: 4,7,13,16,21,24-hexaoxa-1,1O-diazabicyclo[8.8.8]hexacosane, (l), ("Kryptofix[22 2]", Merck Products, Darmstadt, Germany):

Structural studies of odd-nylon crystals grown from solution

“…Shifting of the sheets by exactly one quarter of the a axis generates an arrangement such that twinning domains, if they exist, become undistinguishable when projected along the c axis of the structure. It should be noted that a similar type of twinning concerning odd nylons had already been observed in the case of even nylons 4 [17] and 6 [18] in a-structure. This is appreciated as additional evidence of the structural resemblance between these two families of nylons.…”

“…The nylon 5 sample used in this work was prepared by anionic ring opening polymerization of piperidinone in the presence of quaternary ammonium salt catalyst as described in detail elsewhere [6]. Samples of nylons 9 and 13 were a kind gift received from Dr Pryde (Department of Agriculture, Peoria, IL, USA).…”

Suspension polymerization of 2‐pyrrolidone in the presence of CO2 and organic promoters

“…However, as declared by Figure 8, the crown ether only accelerated the Figure 8(a) is contrary to that reported in bulk polymerization where crown ethers proved simultaneously promoted the conversion and [η]. 20,21 The deviation may be attributed to the different compositions in bulk and suspension reaction systems. It is speculated that the decrease in [η] observed herein was related to SDS which is absent from bulk polymerization.…”

“…step, as shown in Scheme 4, which led to higher yield and [η]. 21 The decrease in yield and [η] at higher TMAC concentrations was probably caused by the termination of high concentrations of chlorine ion. 22…”

“…19 By utilizing either macroheterobicyclic compounds or quaternary ammonium salts to enhance catalytic activity, Robert et al synthesized PBL with both high MW and high yield. [20][21][22][23] Although these works contribute in improving the yield and MW of PBL, the solidification and agglomeration of the products have not yet been overcome. To remove the solidified products from the reactor, a large amount of solvent, such as formic acid (FA), is required to dissolve the hardened cluster over a long period of time and then precipitate PBL in a large amount of nonsolvent.…”