The photophysical and ion-sensing properties of densely grafted conjugated polymer poly-p-phenylene-g-poly(2 (methacryloyloxy)ethyl)trimethylammonium chloride (PPPV-g-PMETAC) are presented herein. The grafted polymer exhibits excellent iodide-sensing which is easily observed using fluorescence Spectroscopy. The iodide detection limit for PPV-g-PMETAC was found to be 10 nM and was independent of temperature and pH <12. The change in fluorescence of PPV-g-PMETAC, upon exposure to iodide, was attributed to polymer aggregation due to changes in the morphology of the grafted PMETAC side chains, which was observed using atomic force microscopic and dynamic light scattering studies. (C) 2018 Wiley Periodicals, Inc.