| Abstract: | Phthalaldehyde was found to undergo cyclopolymerization with ease by several cationic catalysts and by γ-ray irradiation. The polymer was composed entirely of the dioxyphthalan unit, as confirmed by infrared spectroscopy and ready decomposition to monomer. The enhanced polymerizability of phthalaldehyde as compared with other aromatic aldehydes was explained in terms of the intermediate-type or, preferably, concerted propagation scheme. The conversion reached a saturation value of 87% in about 1 hr in methylene chloride at ?78°C, indicating an equilibrium polymerization. The ceiling temperature of the polymerization was ?43°C, as estimated from the relation between the saturation yield and polymerization temperature. The enthalpy and entropy of propagation were ?5.3 kcal/mole and ?23.0 eu, respectively. Since the molecular weight of the polymer was proportional to conversion, the propagating chain end was considered to be “living” in this system. The rate constant for propagation was calculated to be 0.18 1/mole-sec in methylene chloride at ?78°C with BF3OEt2 catalyst. |
