Investigation of the oxidation of the polybenzoxazole from 3,3′-dihydroxy-4,4′-diaminodiphenylmethane and isophthalyl dichloride☆

Oxidation of the polybenzoxazole from 3,3′-dihydroxy-4,4′-diaminodiphenylmethane and isophthalyl dichloride, occurring during heat treatment at 240–350°C has been investigated. It is shown that at 240–300°C it is mainly the aliphatic groups of the polybenzoxazole that undergo oxidation. At 260°C the degree of substitution of the benzene nucleus in the aromatic fragments of the polymer chain begins to change, and above 300°C this can lead to degradation (especially above 350°C). Some characteristics of the network structure of the polymer formed during oxidation were calculated. The composition of the volatile oxidation products was determined and a mechanism of oxidation of the polybenzoxazole is proposed.