The thermal stability of PPA is highly dependent on whether the polymer is end-capped or isolated without end groups. Cyclic PPA, in addition to functionalized linear PPA chains are known to be thermally stable for up to 150C as determined by both Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Moreover, the polymer is known for its long-term shelf life wherein it can be stored at room-temperature for a significant amount of time. Various chemists have studied substitution effects on the thermal stability of PPA. For instance, scientists at The International Business Machines Corporation (IBM) concluded, after extensive studies, that o-phthalaldehyde monomers functionalized with chloro, bromo, and 4-trimethylsilyl functional groups result in highly stable PPA compared to the unsubstituted polymer. Similarly, Phillips et al. proved that the substituted and end-capped poly(4,5-dichlorophthalaldehyde) possesses higher thermal degradation temperatures than its unsubstituted counterparts.