Thermal oxidative and photo‐oxidative degradation of polytetrahydrofuran studied using ¹H NMR, ¹³C NMR and GPC

Abstract

The products and mechanism of the thermal oxidative degradation at 180 °C and the photo‐oxidative degradation at 40 °C of polytetrahydrofuran have been investigated using 1H NMR, 13C NMR and GPC. The NMR analysis was assisted by the use of DEPT 13C spectra, two‐dimensional NMR spectroscopy (COSY, HMQC and HMBC) and chemical shift simulation software. The NMR spectra of both thermally and photolytically degraded samples were similar showing that the degradation mechanisms were similar. GPC indicated that both chain scission, leading to lower molar mass products, and chain extension, leading to higher molar mass products, occurred initially. NMR analysis of the initial soluble degraded polymers showed that chain scission resulted in formate, aldehyde, propyl ether, butyl ether and propanoyl chain ends, and in‐chain ester groups were also formed. For longer periods of degradation, crosslinked gels were formed but these were not amenable to detailed structural characterisation by high‐resolution NMR to determine the crosslink mechanism. Copyright © 2004 Society of Chemical Industry

Assignment of 1H NMR spectrum and investigation of oxidative degradation of poly(ethylenimine) using 1H and 13C 1‐D and 2‐D NMR

“…The formation of formamides is analogous to the formation of formates in the oxidative degradation of PEO11–13 and PTHF14 and a similar mechanism may be proposed (Scheme ) involving chain scission of an initially formed hydroperoxide. The quaternary carbonyl peaks presumably arise from in‐chain amides formed (Scheme ) in an analogous manner to in‐chain esters in the degradation of PEO13 and PTHF,14 i.e. by dehydration of the hydroperoxide according to the following reaction: …”

“…This paper reports a study of the oxidative thermal and UV degradation of PEI using 1 H and 13 C NMR, including both one‐dimensional (1‐D) and two‐dimensional (2‐D) techniques. Such techniques have been fruitfully applied to the oxidative degradation of poly(ethylene oxide) (PEO),11–13 poly(propylene oxide),11 and polytetrahydrofuran (PTHF) 14. The objectives of this work were (i) to characterise the mechanism of thermal and UV degradation and (ii) to provide a ready source of reference data by means of which other workers may characterise the structure of PEI prepared and/or used in other studies in which degradation may occur.…”

Nanostructured Rhenium–Carbon Composites as Hydrogen-Evolving Catalysts Effective over the Entire pH Range

“…To synthesize Re/C nanocomposites (Scheme ), Re 2 O 7 powder (99.995%, Alfa Aesar) was first dissolved in THF, and the 0.4 M solution was kept at ambient conditions for 24 h. This transparent solution gradually changed into a dark, viscous “gel” (for macroscopic image, see Figure S1), whose formation can be attributed to ring opening polymerization (ROP) of the THF molecules initiated by concentrated Re 2 O 7 acting as a Lewis-acid. , As illustrated by the TEM images in Figure S2, the initially dispersed Re 2 O 7 nanocrystals gradually aggregated by polymerizing THF and ultimately formed networks of NPCs a few-hundred-nm in size. Cross-linking of Re 2 O 7 by the possibly “opened” THF molecules is evidenced (i) by 1 H–NMR proton signals from the polymerized THF at 3.44 and 1.64 ppm (vs 3.77 and 1.88 ppm in THF monomers; see Figure S3a) and (ii) in FT-IR, by the appearance of a strong C–O stretch at 1108 cm –1 , which likely comes from aliphatic ether (vs 1068 cm –1 ring stretch of THF monomer; see Figure S3b).…”

Design of a Boron-Containing PTHF-Based Solid Polymer Electrolyte for Sodium-Ion Conduction with High Na+ Mobility and Salt Dissociation

“…The signals a′ (30.0 ppm) and a″ (26.6 ppm) correspond to the carbons bonded with protons a, with a′ being the closest to the hydroxyl. Signals c′ and d′ correspond to the carbons associated with protons c and d, respectively 26. The peak at 112.7 ppm has been assigned to the central tertiary carbon in the C-PTHF, confirming the structure of interest 27.…”