Mazen Garaleh

Tertiary Amine‐Initiated Zwitterionic Polymerization of Pivalolactone—A Reinvestigation by Means of MALDI‐TOF Mass Spectrometrya

When pyridine, 4‐methylpyridine (4‐MP) and 4‐(N,N‐dimethylamino)pyridine (DMAP) were used as initiators for the polymerization of pivalolactone in N‐methylpyrrolidone, linear chains having one pyridinium ion and one CO2 ⊖ ion as endgroups were found to be the main reaction products. The absence of cyclic oligolactones, even at temperatures up to 140°C, proves that the chain growth of the zwitterionic chains proceeds exclusively by anionic ring‐opening polymerization. When dichloromethane was used as a reaction medium, part of the polylactone chains had –CO2CH2Cl endgroups due to side reactions with the solvent. With diazabicyclooctane as initiator, a clean zwitterionic polymerization was found in NMP. With triethylamine or 2‐ethyloxazolidine as initiators, the zwitterionic/anionic ring‐opening polymerization was again the prevailing process, but significant side reactions also took place. In the case of 2‐ethyloxazolidine, these side reactions included the formation of cyclic oligolactones. In the case of β‐propiolactone, complete elimination of the pyridinium ions with formation of acrylate chain ends was observed. a“Polylactones” Part 65

Hafnium Chloride Catalyzed Polycondensation of α,ω-Alkanediol with Dicarboxylic Acids or Succinic Anhydride

Three different kinds of polycondensation were preformed and the usefulness of HfCl4.2THF as estrification and polycondensation catalyst was evaluated. It was compared with HfCl4, BiCl3, LaCl3 and SnCl2. In polycondensations of 1,6-hexandiol, and 1,10-decandiol with various dicarboxylic acids all catalysts failed to give satisfactory results. However, in polycondensations of 1,4-butanediol with succinic anhydride in refluxing decalin good results were obtained, and HfCl4.2THF was the most effective catalyst after SnCl2. The MALDI-TOF mass spectra revealed that cyclization made a significant contribution to the limitation of the chain growth.