Hyperbranched fluorocopolymers were synthesized by the atom transfer radical self-condensing vinyl copolymerization (ATR-SCVCP) of an inimer, either p-chloromethylstyrene (CMS) or p-bromomethylstyrene (BMS), with 2,3,4,5,6-pentafluorostyrene (PFS), with 2,2-bipyridine together with CuCl or CuBr as the ligand/ catalyst system. The reaction conditions were studied to provide for control over the copolymer compositions, molecular weights, degrees of branching, and properties, as characterized by H-1, C-13, and F-19 NMR spectroscopy, gel permeation chromatography, elemental analysis, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and solubility tests. Copolymers having number-average molecular weights from 2.9 to 260 kDa and polydispersities (weight-average molecular weight/ number-average molecular weight) from 1.8 to 4.8 were obtained. The molar fractions of PFS units increased with increases in the feed ratio of PFS to the inimer. The degrees of branching were typically about 30% with the feed of 1.0 or 2.0 equiv of PFS with respect to the inimer, although slight variations could be achieved through the variation of the inimer composition. Under similar reaction conditions with CuCl as the catalyst, ATR-SCVCP of BMS with PFS led to higher degrees of branching than ATR-SCVCP of CMS with PFS. Solubility tests indicated that the polymers prepared under conditions that avoided extensive biradical coupling were soluble in a broad range of organic solvents. (c) 2005 Wiley Periodicals, Inc.