Degradation of polytetramethylene oxide. I. Thermally‐induced

Abstract

The thermal degradation of polytetramel hylene oxide has been examined in detail. The polymer contained weak links which led to facile chain scission on heating (50 to 150'C.). The activation energy of this degradation process in xylene solution is 13.3 kcal. Imol. The. available evidence indicates that the weak links are hydroperoxide groups formed in the presence of air. These groups could be destroyed by heating in vacuum, the resultant degree of degradation of the polynier depending on the number of hydroperoxide groups present.Measurements of the intrinsic viscosity of polytetramethylene oxide, freed from weak links, showed that the polymer underwent random chain scission a t elevated temperatures according to the equation:The exponent, a, of the KUHN-HOUWINK equation was thus determined to be 0.75 for the polymer in benzene a t 20°C. Analysis of the molecular weight changes occurring during degradation at various temperatures showed that the chain scission process obeyed first order kinetics and could be expressed by the rate equation: k = 1.98 . 1017e-49,700/RT This result is compared with activation energies obtained by thermogravimetry in air and vacuum. ZUSAMMENFASSUNG:Es wurde der thermische Abbau von Polytetrarnethylenoxid untersucht. Das Polymerc enthielt schwache Bindungen, die beim Erwarmen auf 50 bis 150°C leicht spalteten. I n Xylol betrug die Aktivierungsenergie dieses Abbauvorganges 13,3 KcallMol. Wie nachgewiesen wurde, sind die schwachen Bindungen Hydroperoxidgruppen, die sich in Gegenwart der Luft bildeten. Diese Gruppen konnten beim Erhitzen im Vakuum zerstort werden; der sich einstellende Abbaugrad des Polymeren hangt voii der Zahl der vorhandenen Hydroperoxidgruppen ab. Messungen der Intrinsic-Viskositat des von schwachen Bindungen befreiten Polytetramethylenoxids zeigten eine regellose Kettenspaltung bei erhohten Temperaturen, die nach der Gleichung verlief : log [q] = -cc.log (t + to) + c *) Presented a t the 148 th American Chemical Society Meeting, Chicago, Illinois, September, 1964. Degradation of Polytetramethylene Oxide. I. Der Exponent a der KuHN-HouwINK-Gleichung wurde fur das Polymere in benzolischer Losung und bei 20 "C zu 0,75 bestimmt. Die Analyse der Molekulargewichtsanderungen wahrend des Abbaus bei verschiedenen Temperaturen ergab, daO die Kinetik der Kettenspaltung erster Ordnung war und dureh folgende Gesehwindigkeitsgleichung erfaRt wurde: 1~ = 1,98.1017 e--49700/RT Dieses Ergebnis wurde mit den Aktivierungsenergien der in Luft und unter Vakuum durchgefiihrten thermogravimetrischen Analyse verglichen.

Polaromicrotribometric (PMT) and Spectroscopic (Infrared‐XPS) Study of the Formation and Modifications of Films Formed on a Polarized Platinum Electrode in THF ‐ LiClO4 Medium: II . Anodic Polarization

“…Such reactJLons have been observed with the bulk polymer in contact with air (19). These are oxidation reactions which entail a fragmentation of the chain and the formation of aldehyde fragments (19). These aldehydic groups may also originate from a secondary polymerization process between the ~/ c a t i o n and the THF + molecules (20,21).…”

“…It is possible that water destroys the radicals which initiate the polymerization It must also be noticed that the infrared and X P S spectra reveal some aldehydic bonds which m a y be attributed to the polymer peroxidation by air. Such reactJLons have been observed with the bulk polymer in contact with air (19). These are oxidation reactions which entail a fragmentation of the chain and the formation of aldehyde fragments (19).…”

Aliphatic Polyethers: Classical Polymers for the 21st Century

“…Furthermore, PTHF is hygroscopic and has to be stored in closed tanks under nitrogen atmosphere. Under elevated temperatures or the presence of oxygen, the polymers undergo degradation and antioxidants like amines or pyrocatechols must be added …”

“…Under elevated temperatures or the presence of oxygen, the polymers undergo degradation and antioxidants like amines or pyrocatechols must be added. [ 180 ]…”

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

“…Several studies of the thermal degradation,1–9 photo‐degradation,10 radiolytic degradation11–15 and persulfate‐induced degradation16 of PTHF have been published, in an inert atmosphere1–9, 15 or in the presence of air or oxygen 3–6, 9–14, 16. The techniques employed included analysis of evolved products by gas chromatography (GC)8, 11–14 and mass spectrometry (MS),1, 2, 9 chemical analysis,11–14 thermogravimetry (TG),2–4 differential scanning calorimetry (DSC),6, 7 differential thermal analysis (DTA),4 infrared spectroscopy (IR)2–4, 10 and monitoring changes in molar mass by viscosity5, 9, 15, 16 or gel permeation chromatography (GPC) 16. The consensus of these studies is that degradation proceeds by a free‐radical chain scission mechanism, though Golden15 noted that cross‐linking also occurred after exposure to high‐energy electrons in vacuo .…”