NMR‐Untersuchungen an Polyacetalen, 3. Sequenzanalyse bei 1,3,5‐Trioxan/1,3‐Dioxolan‐Copolymeren durch ¹³C‐NMR‐Spektroskopie

Abstract

1H‐NMR‐Spektren von 1,3,5‐Trioxan/1,3‐Dioxolan‐Copolymeren zeigen für die Methylenoxidbausteine Triadensequenzen an, während für die Äthylenoxidbausteine praktisch keine Sequenzabhängigkeit beobachtet wird. In 13C‐NMR‐Spektren werden sowohl für die Methylenoxid‐ als auch für die Äthylenoxidbausteine Pentadensequenzen gefunden. Niedrige Konzentrationen an Verschiebungsreagenz (Eu(fod)3) in den NMR‐Proben ermöglichen die Identifizierung aller Pentadensequenzen, höhere Konzentrationen an Eu(fod)3 bewirken für beide Grundbausteine eine Aufspaltung der Signale in Heptadensequenzen.

Synthesis of copolymer from 1,3,5‐trioxane and 1,3‐dioxolane catalyzed by Maghnite‐H+

“…Various investigators have presented two methods for determining the comonomer content: gas chromatography 29,30 and NMR spectroscopy. [31][32][33] The ring-opening copolymerization of TOX can be initiated by Lewis acid such as BF 3 O(Et) 2 , TiCl 4,34 and CH 3 COClO 4 . 35 Penczek and coworkers 36 studied the solution copolymerization of TOX and a small amount of DOX initiated by BF 3 O(n-Bu) 2 and found that the unstable fraction content of the copolymer increased with increasing conversion, indicative of a higher reactivity of DOX than that of TOX toward the copolymerization.…”

1H‐NMR investigation of the thermooxidation degradation of poly(oxymethylene) copolymers

“…The properties of POM copolymers depend on the comonomer composition and also on the sequence distribution of the constituent comonomers, which can range from alternating to random to blocky. Various investigators have presented two methods for determining the comonomer content: gas chromatography3, 4 and NMR spectroscopy 5–7. Concerning the comonomer content, both methods are satisfactory, except when very exact values are required.…”

Ionic Polymerization

“…NMR and stability studies, that the comonomers are randomly distributed along the chains [237,238]. This is attributed to the fact that intermolecular chain transfer (transacetalization), contrary to THF polymerization, proceeds on a time scale similar to propagation, and the same holds for the intramolecular chain transfer leading to cyclic polymer [239,240].…”