We functionalize the focal group of hyperbranched poly(phenylene sulfide) (HPPS) with benzyl, phenyl, and naphthyl group, respectively. DSC analysis shows that T-g of HPPS is increased from 55 to 93 degrees C by functionalization of the focal group with a conjugated naphthyl group. The fluorescence properties of the three core-functionalized HPPS' are studied under the comparison with the original HPPS. Functionalization by a non-conjugated benzyl group has no effects on the fluorescence properties of HPPS at all. Both the phenyl-cored and the naphthyl-cored HPPS' give rise to a new highly polarized fluorescent peak around 500 nm due to the formation of intermolecular excimers with encumbered molecular rotation. Differing from the often reported significant increase in core fluorescence due to the so-called "antenna effect," the fluorescence of HPPS backbones is drastically enhanced after functionalization of the cores with naphthyl groups that is 10- to 18-fold higher than the original HPPS' depending on the molecular weights of HPPS'. The phenyl-cored HPPS does not show a notable increase in fluorescence intensities compared with the original HPPS. The clear comparison results are rationalized by the restriction of intramolecular rotations of the naphthyl cores against the HPPS periphery. (c) 2007 Wiley Periodicals, Inc.