title: Conjugated polyelectrolytes with guanidinium side groups. Synthesis, photophysics and pyrophosphate sensing.
abstract: Two cationic poly(phenylene ethynylene) conjugated polyelectrolytes (CPEs) featuring guanidinium side groups were the subject of investigation. Two polymers were examined, one is an alternating co-polymer (P1) in which the guanidinium groups are on every other repeat unit and the second is a homopolymer with the guanidinium groups on every repeat unit. The photophysical properties of the CPEs were investigated in CH3OH and H2O solution by absorption, steady-state fluorescence and fluorescence lifetime spectroscopy. The results indicate that P1 and P2 are molecularly dissolved in CH3OH solution; however, in water the polymers aggregate as evidenced by a substantial reduction in the fluorescence yield. Addition of the non-ionic surfactant (Triton X-100) into the weakly fluorescent aqueous solution of P1 increased the fluorescence by forming a polymer/surfactant complex. The fluorescence of the polymer/surfactant complex in aqueous solution was effectively quenched by the addition of pyrophosphate (PPi) with Stern-Volmer quenching constants (K(sv)) ∼ 1.7 × 10(5) M(-1); the quenching occurs because PPi binds to the guanidinium groups and induces the aggregation of the polymer/surfactant complex. In addition, by using fluorescence correlation spectroscopy it was found that the diffusion time of the aggregated complex is increased 9-fold in comparison with the free CPE/surfactant complex. A sensor is developed utilizing the significant changes in fluorescence induced by the addition of PPi.
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA. kschanze@chem.ufl.edu.
authors.forename: Xuzhi
authors.initials: X
authors.lastname: Zhu
authors.forename: Jie
authors.initials: J
authors.lastname: Yang
authors.forename: Kirk S
authors.initials: KS
authors.lastname: Schanze