NMR-Untersuchungen an Polyacetalen, 4. Sequenzanalyses von Homo- und Copolymeren des 1,3,5-Trioxepans

Abstract

1,3,5‐Trioxepan (1) ist kationisch leicht polymerisierbar. Aus den 1H‐NMR‐Spektren (Triadensequenzen) und den 13C‐NMR‐Spektren unter Zusatz von Eu(FOD)3 (Pentaden‐und Heptadensequenzen) wird deutlich, daß die Mikrostruktur von Polytrioxepan identisch ist mit 1,3,5‐Trioxan (2)/1,3‐Dioxolan (3)‐Copolymeren. Ein Mechanismus für die Polymerisation von 1 wird diskutiert. Bei der Copolymerisation mit 3 wird 1 bevorzugt in das Copolymere eingebaut.

Modifying Li+ and Anion Diffusivities in Polyacetal Electrolytes: A Pulsed-Field-Gradient NMR Study of Ion Self-Diffusion

“…The 1 H NMR spectrum of P­(EO-2MO) shows that the polymer retains a 1:2 ratio of EO/MO units but reveals three distinct acetal resonances in a 1:2:1 ratio. Subsequent 13 C and heteronuclear single-quantum correlation (HSQC) NMR experiments identify the acetal resonances as (1) EO- MO -EO, (2) EO- MO -MO or MO- MO -EO, and (3) MO- MO -MO sequences in the polymer backbone, similar to previous reports . Differential scanning calorimetry (DSC) demonstrates that all neat polymer compositions have similar T g values (−62 to −66 °C); however, melting temperatures ( T m = 20–58 °C) and semicrystalline behavior vary significantly with polymer composition (Figures S2–S6).…”

“…Therefore, we tuned monomer concentration and equivalents of MeOTf or TMSOTf to obtain comparable molecular weights ( M n = 13.6–24.9 kDa) for poly­(1,3,6,9-tetraoxacycloundecane) (P­(3EO-MO)), poly­(1,3,6-trioxocane) (P­(2EO-MO)), poly­(1,3-dioxolane) (P­(EO-MO)), and poly­(1,3,5-trioxepane) (P­(EO-2MO)) (Table S1). Poly­(1,3,6,9,12-pentaoxacyclotetradecane) (P­(4EO-MO)) reached a molar mass of only 5.2 kDa, likely because low ring strain in 14-membered 4EO-MO prevents high conversion. ,, The polymers were obtained in moderate yields (56–70%), and all data match previous reports of P­(4EO-MO), ,, P­(3EO-MO), ,,− P­(2EO-MO), ,,, P­(EO-MO), and P­(EO-2MO) …”

“…50,51,56 The polymers were obtained in moderate yields (56−70%), and all data match previous reports of P(4EO-MO), 50,51,56 P(3EO-MO), 50,51,56−58 P(2EO-MO), 39,40,59,60 P(EO-MO), 54 and P(EO-2MO). 61 Typically, polyacetals exhibit poor thermal stability, presumably because residual acidic species catalyze ring-closing depolymerization at elevated temperatures. 33 To improve thermal stability, we employed an alkoxide quenching agent, sodium 2-trimethylsilylethoxide (NaOEtTMS), which is readily soluble in hexanes and ether and is easily removed during polymer precipitation (Scheme 1).…”

“…Subsequent 13 C and heteronuclear single-quantum correlation (HSQC) NMR experiments identify the acetal resonances as (1) EO-MO-EO, (2) EO-MO-MO or MO-MO-EO, and (3) MO-MO-MO sequences in the polymer backbone, similar to previous reports. 61 Differential scanning calorimetry (DSC) demonstrates that all neat polymer compositions have similar T g values (−62 to −66 °C); however, melting temperatures (T m = 20−58 °C) and semicrystalline behavior vary significantly with polymer composition (Figures S2−S6). Notably, P(3EO-MO) is amorphous (Figure S3), whereas P(4EO-MO) exhibits unique crystallization behavior during the second heating step (Figure S2).…”