text: Although a less known polymerization technique, coordinative polymerization has been used a few times in PPA preparation. It mostly requires the activation of transition metal catalysts with trimethylaluminum or diethyl aluminum chloride and allows a control over the stereoselectivity of the compound. Another advantage of this technique lies within the usage of water as a co-catalyst in PPA synthesis which is deemed impossible in other polymerization methods. Professor Hisaya Tani from the Department of Polymer Science at Osaka University was the first to report a stereospecific polymerization of o-phthalaldehyde by employing dimeric dimethylaluminumoxybenzylideneaniline [MeAlOCMeNPh] as catalyst and water as a co-catalyst. He was able to synthesize a fibrous PPA in exclusively trans-configuration which had never been reported before. Nonetheless, due to the inability to endcap the polymer with functional groups, this technique is rarely utilized at present and the mechanism of formation of PPA remains ambiguous and not well studied.