Mechanistic Study of Rhodamine B Piezocatalytic Decomposition Using Poly(vinylidene difluoride) and Related Polymers

Membranes of poly(vinylidene difluoride) (PVDF) and relatedpolymersare used as piezoelectric materials to decompose rhodamine B (RhB)under low power sonication. The change in the visible spectrum ofRhB allows determination of the rate constants for different polymercompositions and membrane thicknesses. The results indicate that thepiezoelectric field generated by mechanical deformation of the polymerscatalyzes the scission of the C-N bond in RhB. When PVDF isdoped with transition-metal nitrates to increase the fraction of thepiezoelectric beta-phase, the rate constants increase, but theanalysis is complicated by concurrent adsorption of RhB onto the membrane.A mechanism consistent with the observed data is proposed where thepiezocatalytic effect of the membrane is to heterolytically cleavethe C-N bond followed by formation of a C-Cl bond onthe new xanthene ring.

Automated summary

Membranes of PVDF and related polymers are used to decompose RhB under low power sonication, and the change in visible spectrum of RhB allows determination of rate constants for different polymer compositions and membrane thicknesses. The piezoelectric field generated by mechanical deformation of the polymer catalyzes the scission of the C-N bond in RhB. Doping PVDF with transition-metal nitrates increases the rate constants, but the analysis is complicated by concurrent RhB adsorption onto the membrane. A proposed mechanism suggests that the piezocatalytic effect of the membrane leads to heterolytic cleavage of the C-N bond followed by formation of a C-Cl bond on the new xanthene ring.