The kinetics of the thermal degradation of isomeric dipropyl and dibutyl esters of poly(itaconic acid)

Non-oxidative and oxidative thermogravimetry was performed on poly(di-n-propyl-) (PDnPI), poly(di-iso-propyl-) (PDiPI), poly(di-n-butyl-) (PDnBI), poly(di-iso-butyl-) (PDiBI) and poly(di-sec-butyl itaconate) (PDsBI). The results show that PDiPI and PDsBI thermally degrade in a similar manner with deesterification being, together with depolymerisation, a significant mechanism. PDnPI and PDnBI also degrade in a similar manner by depolymerisation, with chain end initiation being more important than random main chain scission initiation. The results for PDiBI indicate more similarity to the n-alkyl esters than to the other branched chain esters although, there are indications that also with this polymer ester decomposition is not an insignificant thermal degradation mechanism. Although little can be said about the mechanism of oxidative thermal degradation of these polymers, the kinetic data again show the similarity between PDnPI and PDnBI on the one hand, and PDiPI and PDsBI on the other. Also, in an oxidative atmosphere, PDiBI shows more similarity to the n-alkyl esters than to PDiPI and PDsBI. It would appear that, as with the polymethacrylates, the number of β-hydrogen atoms in the ester substituents plays a dominant role in determining the mechanism of both the thermal and thermo-oxidative degradation of these polymers.