Multihydroxyl Branched Polyethers. 2. Mechanistic Aspects of Cationic Polymerization of 3-Ethyl-3-(hydroxymethyl)oxetane

Abstract

This paper, second in a series, reports the cationic polymerization of 3-ethyl-3-(hydroxymethyl)oxetane leading to branched polyethers containing exclusively methylol groups attached to the quaternary carbon atoms (primary hydroxyl groups). GPC chromatograms and MALDI TOF spectra of the isolated polymers demonstrated that intramolecular chain transfer to polymer occurred, providing a cyclic fragment of the macromolecule. This limited the chain growth and thus the molecular weight of resulting polymers. The phosphorus cation-trapping method showed that both secondary and tertiary oxonium ions were present in the polymerization mixture, indicating that both active chain end (ACE) and activated monomer (AM) mechanisms contributed to the chain growth. As a consequence of the coexistence of two propagation mechanisms and significant chain transfer, both molar mass and degree of branching depended only slightly on the polymerization conditions.

Ring opening polymerization of 3-semifluoro- and 3-bromomethyloxetanes to poly(2,2-substituted-1,3-propylene oxide) telechelics for soft blocks in polyurethanes

“…Poly(2,2-substituted-1,3-propylene oxide)s with controllable molecular weights were prepared using BF 3 -etherate and 1,4-butanediol as a cocatalyst [31]. Ring-opening of hydroxymethyloxetanes catalyzed using BF 3 complexes has been studied by Bednarek [32,33]. Oxetane telechelics with semifluorinated side chains were synthesized using cationic ring opening polymerization in several ways [16,17,34].…”

Poly(ethylene glycol)-armed hyperbranched polyoxetanes for anticancer drug delivery

“…18 A three-necked round bottom flask was placed on a heating mantle at 100 °C under a nitrogen purge for 30 min. Subsequently, a temperature of 45 °C was maintained during the reaction.…”

Hyperbranched aliphatic polyether polyols

“…47 Both molar mass and DB depend only to a low extent on the polymerization conditions, because significant chain transfer and the coexistence of two propagation mechanisms limit the growth of the polymer. 82 In MALDI-TOF MS spectra only cyclic polymer structures are found. A possible explanation are intramolecular chain transfer reactions of hydroxyl groups.…”

“…This observation is explained by strong hydrogen bonding between multiple hydroxyl groups of the polymer. 82 By carrying out the polymerization in ionic liquids, Biedron et al tried to reduce the interfering influence of the hydroxyl groups. 83 However, despite higher yields, the molecular weight of the polymers could not be increased.…”