In particular, Moore and coworkers conducted rigorous mechanistic studies on poly(phthalaldehyde) by modifying the type of catalyst used, as well as the starting monomer concentration in an effort to control the molar mass, decrease the polydispersity index, and increase the polymer’s purity. Among the catalysts used were triethyloxonium borofluoride, tin chloride, and triphenylmethylium tetrafluoroborate. Limitations While LCP was the first and sole method used to produce poly(phthalaldehyde), its usage nowadays has dramatically decreased in favor of other polymerization techniques which allow a better control over the polymer properties including molar mass and thermal stability. Living anionic polymerization (LAP) History and main idea While this polymerization technique did not typically gain fame and popularity until 2010, it was also reported by Aso and Tagami in 1969. In general, LAP involves the usage of a strong nucleophile to initiate polymerization in addition to the employment of an electrophile as a terminator to endcap the polymer chain. In Tagami’s article, PPA was prepared by utilizing tert-butyllithium as an initiator and acetic anhydride as a terminator. However, the drawbacks faced when utilizing LCP (low polydispersity index (PDI), low yield, and no control over molecular weight) were also encountered in this polymerization technique. Current trends It was not until 1987 when two chemists, Hedrick and Schlemper, from the University of Freiburg proposed the use of phosphazene bases to speed up the reaction and lower the polydispersity index. Up until 2023, three different phosphazene bases have been used in PPA polymerization (Figure 3). Moreover, most of the published research articles describing PPA synthesis between 2008 and 2023 revolve around the usage of LAP, rendering it the most common and effective polymerization technique. Advantages The major advantage this polymerization technique presents over LCP lies in the fact that the polymer can be end capped on both sides of the chain with stimuli-responsive groups. The tuning process of PPA by these functional groups have not only expanded the set of applications this polymer can be used in, but has also improved its properties and attributes. For instance, by controlling the o-phthalaldehyde monomer/alcohol initiator concentration ratio, ultra-high molecular weights (50-150 KDa) PPA can be obtained. Furthermore, PPA synthesized through LAP is more thermally and mechanically stable. Generally, the presence of endcaps on both ends stabilizes the polymer and results in a more flexible chain with a high thermal stability. And because linear polymers synthesized by LAP method can be