Cationic Polymerization of Cyclic Amines

Abstract

It is now generally accepted that the propagation reaction in the cationic ring-opening polymerization of cyclic amines is a nucleophilic attack of the monomer nitrogen on a strained cyclic ammoni um salt which is the active species of the growing macromolecule. The driving force of the polymerization is the relief of strain associated with the ring-opening of the active chain end. The resultant polymer molecules, however, also contain nucleophilic amino functions and therefore the polymer competes with monomer to react with the active species. This results in the formation of a (linear or cyclic) non-strained and therefore non-reactive ammoni um salt.With secondary cyclic amines (R=H), the proton on the terminated ammoni um salt as well as the proton on the active species can be transferred to other amino groups present in the mixture including monomer. Dimers and other low oligomers are therefore the initial products, and the final products are branched polymers containing a distribution of primary, secondary and tertiary amino functions (1, 2).With cyclic tertiary amines (R = alkyl), the formation of a non-strained ammoni um salt is a real termination reaction. If the rate of this termination reaction is not negligably small compared with the rate of the propagation, in other words if the ratio kp/kt is not very high, the polymerization will stop before 1

Cationic ring-opening polymerization of N-phenylazetidine

“…The lower value of DH t m compared to DH p in the polymerization of NPA may be ascribed to the higher reactivity of an acyclic anilino-amino group (e. g. pKa = 4.39 for N,N-dimethylaniline) [22] relative to cyclic NPA (pK a = 4.08), [22] in contrast the polymerization of NMA, where the reactivity of cyclic NMA (pK a = 10.4) [23] is estimated to be very close to an acyclic alkylamino group (e. g., pK a = 10.29 for diethylmethylamine). [23] The entropic contribution, on the other hand, is remarkable in the polymerization of NPA, by comparing with the polymerization process of NMA. Thus, the DS m p values for both polymerization systems of NPA and of NMA are close to each other, and the corresponding DS m t values are notably more negative.…”

“…An N-phenylazetidinium salt is considered to possess a higher ring-opening reactivity than the relevant N-alkylazetidinium salt, since aniline derivatives are known to be better leaving groups than alkylamino groups in an S N 2 reaction, while N-phenylazetidine is assumed to be less nucleophilic than Nalkylazetidines by comparing their pK a values, i. e. 4.08 for N-phenylazetidine (NPA) [22] and 10.4 for N-methylazetidine (NMA). [23] In this connection, we have recently observed that an N-phenylpyrrolidinium salt group, thus a five-membered cyclic ammonium salt group, displays a notably higher ring-opening reactivity than an N-methylpyrrolidinium salt group. [24][25][26] Hence, we have herewith investigated the cationic polymerization of NPA, hoping to achieve rapid and quantitative polymerization under ambient conditions.…”

Aziridines and azetidines: building blocks for polyamines by anionic and cationic ring-opening polymerization

“…N-Substituted aziridines can also be obtained if secondary amines are used as starting material. [95][96][97]…”

Ring-Opening Polymerization—An Introductory Review

“…Typical examples are the reactions of trialkyl oxonium ions with cyclic acetals [38], ethers [52], or sulfides [53] as well as with amines [54].…”