Cyclic and multicyclic polymers by three-dimensional polycondensation.
The recent confirmation that polycondensations (and other step-growth polymerizations) of difunctional monomers involve cyclization reactions at any concentration and at any stage of the polymerization also has consequences for three-dimensional polycondensations on multifunctional monomers. It is demonstrated that tree-shaped (hyperbranched) oligomers are gradually transformed into star-shaped polymers with a cyclic core, when the conversion increases. Polycondensations of "a(2) + b(3)" or "a(2) + b(4)" monomer combinations yield multicyclic polymers, when gelation can be avoided. This new architecture may be subdivided into three groups: perfect multicycles free of functional groups, multicycles having b functions, and multicycles having "a" groups. The concrete examples discussed in this Account mainly concern polyethers and polyesters.
Kricheldorf
Hans R
HR
Institut für Technische and Makromolekulare Chemie, Bundesstrasse 45, 20146 Hamburg, Germany. kricheld@chemie.uni-hamburg.de