Aggregation-mediated optical properties of pH-responsive anionic conjugated polyelectrolytes.
Conjugated polyelectrolyte copolymers containing 2,1,3-benzothiadiazole- (BT) and oligo(ethylene oxide)-substituted fluorene and phenylene units have been designed and synthesized. The phenylene pendent groups also have carboxylic acid functionalities, which allow probing the effect of pH on optical properties. The BT content in the backbone can be regulated at the synthesis stage. Dynamic light scattering studies show that polymers aggregate in water at low pH. Increased interchain contacts give rise to a lowering of the photoluminescence (PL) efficiency via self-quenching when the BT units are absent and increased levels of FRET from the phenylene-fluorene segments to BT. Furthermore, the PL efficiency of BT increases in the aggregated structures. Examination of solvent effects indicates that the increased BT efficiencies are likely due to decreased contact with water. The changes in PL efficiencies are reversible, showing that the aggregates are dynamic and not kinetically constrained.
Wang
Fuke
F
Department of Materials and Chemistry & Biochemistry, Institute for Polymers and Organic Solids, University of California, Santa Barbara, California 93106, USA.
Bazan
Guillermo C
GC
D000838:Anions / Q000737:chemistry; D052160:Benzothiazoles / Q000737:chemistry*; D015374:Biosensing Techniques / Q000379:methods; D004573:Electrolytes / Q000138:chemical synthesis*; D005449:Fluorenes / Q000737:chemistry*; D031541:Fluorescence Resonance Energy Transfer; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D049449:Luminescence; D015394:Molecular Structure; D055095:Optics and Photonics; D011108:Polymers / Q000138:chemical synthesis* / Q000737:chemistry; D012542:Scattering, Radiation; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
D000838:Anions; D052160:Benzothiazoles; D004573:Electrolytes; D005449:Fluorenes; D011108:Polymers; D012997:Solvents; C473966:poly(phenylene ethynylene); D014867:Water