A New Class of Conjugated Ionic Polyacetylenes. 3. Cyclopolymerization of Alkyldipropargyl(4-sulfobutyl)ammonium Betaines by Transition Metal Catalysts

A new type of conjugated ionic polyacetylene was synthesized by metathesis polymerization of betaine monomers, alkyldipropargyl(4-sulfobutyl)ammonium betaines (ADPSAB). The alkyl groups used are ethyl, n -butyl, n -hexyl, and n -octyl. The polymerization of ADPSAB was carried out with various transition metal catalyst systems such as MoCl 5 -, WCl 6 -, and PdCl 2 -based catalyst systems. The MoCl 5 and PdCl 2 were found to be particularly effective catalysts for the cyclopolymerization of the betaine monomers. 1 H-NMR, 13 C-NMR, IR, and UV−visible spectroscopies showed that poly(ADPSAB) possess polyene structure having cyclic recurring units in the polymer backbone. Unlike polyelectrolyte, the resulting polymers were more soluble and showed higher viscosities in the salt solution than in salt-free solution (antipolyelectrolytes). When doped with an acceptor such as iodine, the polymers exhibited a substantial increase (∼10 -3 S/cm) in electrical conductivity compared to the undoped state (∼10 -10 S/cm).