Direct mass spectrometry of polymers. XI. Primary thermal fragmentation processes in aromatic–aliphatic polyesters

Abstract

The thermal decomposition of two series of isomeric aromatic–aliphatic polyesters was studied by direct pyrolysis‐mass spectrometry. The results indicate that intramolecular exchange reactions predominate in the primary thermal fragmentation processes to cause the formation of cyclic oligomers. Several secondary thermal processes may occur after the primary step: hydrolytic cleavage of the ester bond, decarboxylation, and β‐hydrogen transfer.

Thermal behavior and crystallization kinetics of random poly(ethylene‐Co‐2,2‐Bis[4‐(ethylenoxy)‐1,4‐phenylene]propane terephthalate) copolyesters

“…The improved thermal stability of PET by introduction of 2,2-bis[4-(ethylenoxy)-1,4-phenylene]propane terephthalate) units along the polymeric chain may be explained as due to the steric hindrance and high stiffness of the counits, which prevent thermal degradation reactions, which usually occur in polyesters when heated. 20,21 An analogous result was obtained previously by us investigating the effect of the introduction of the 2,2-bis[4-(ethylenoxy)-1,4-phenylene]propane terephthalate comonomeric units on the thermal stability of PBT. 16 The influence of molecular weight (M w ) on the glass transition and melting phenomena of the samples under investigation can be excluded, having PET and PET/BHEEBT polyesters high and similar M w values.…”

Isolation and identification of cyclic oligomers of the poly(ethylene terephthalate)–poly(ethylene isophthalate) copolymer

“…The [GI] 2 dimer was recrystallized in trifluoroacetic acid, and Figure 3 shows scanning electron microscopy (SEM) micrographs of [GI] 3 and [GI] 2 crystals. Foti at al 22. studied the thermal decomposition of two series of isomeric aromatic–aliphatic polyesters by direct pyrolysis/mass spectrometry.…”

Thermal degradation of polymer systems having liquid crystalline oligoester segment

“…Blends of oligoester with the commercial polystyrene did not present any shift on the melting or isotropization temperature. [11][12][13] . These results clearly indicate an extensive miscibility in the polystyrene amorphous phase, in the block copolymer or polymer blend.…”

“…The degradation proceeds by free radical mechanism after the primary breakage of the ester linkage of the terephthalic acid ( Figure 1). This mechanism involves a cyclic transition state with the hydrogen at the β position, followed by a chain rupture process in which vinyl ester groups and carboxylic acids are formed [11][12][13] (Figure 1). A second stage was reported to be the thermal scission of the mesogenic group with phenylenic residues formation.…”