As predicted by P. J. Flory seventy years ago, a2 + b4 polycondensations involve a higher risk of crosslinking than analogous a2 + b3 polycondensations. Two scenarios were studied, namely equimolar polyconcendsations and equifunctional polycondensations. Two overriding trends were observed. Firstly, the tendency of gelation increased with higher a2/b4 ratios between equimolar and equifunctional feed ratios. Secondly, the risk of gelation was diminuished due to cyclization reactions, when the monomer concentration was reduced. Equimolar polycondensations of dimethyl sebacate and pentaerythritol in bulk yielded soluble, hyperbranched polyester only, when the conversion was stopped at 92%. Soluble, branched polyethers were obtained at higher conversions, when the monomer concentration was lowered, but most reaction products had a cyclic structure. Several equifunctional polycondensations were performed in solution using nucleophilic or electrophilic b4 monomers. When the initial monomer concentration was optimized to avoid gelation, perfect multicyclic polyesters or polyethers, bar of functional groups, were obtained and characterized by MAL�DI-TOF mass spectrometry. Properties and potential applications of the multicyclic polymers are shortly discussed.

A<sub>2</sub> + B<sub>4</sub> polycondensations

245th National Meeting (2013)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

A2 + B4 polycondensations

A₂ + B₄ polycondensations