Synthesis, characterization, and thermal properties of poly(trimethylene-1,1-dicarboxylate) polyelectrolytes

The potassium salt of poly(trimethylene-1,1-dicarboxylic acid), the first m ember of a new polyelectrolyte family where the carbon backbone is substitu ted on every third carbon by two carboxylate anions, was obtained by hydrol ysis of a monodisperse di-n-propyl ester polymer (CH2CH2C(COOnPr)(2))(n). T his precursor can be synthesized by anionic ring-opening polymerization of di-n-propylcyclopropane-1,1-dicarboxylate using a polymerization procedure already proved to be living for a similar cyclopropyl monomer. The polyelec trolyte potassium salt was fully characterized by solid-state C-13 NMR, FT- IR, elemental analysis, and thermogravimetry; (TGA), providing clear eviden ce for a very selective and clean hydrolysis. The malonate ion substructure on the polymer is very stable and does not decompose below 350 degreesC. N o procedure could be identified to cleanly decarboxylate the polymer to the monosubstituted system. The polymer is very insoluble in water unless high concentrations of potassium hydroxide are used (> 1 mol L-1), a behavior c onsistent with the very high symmetry of the polymer and its high tendency to crystallize.