Branched polyacrylonitrile (PAN) was prepared through a self-condensing vinyl copolymerization of acrylonitrile and 2-(2-bromopropionyloxy)ethyl acrelate (BPEA). The branched architecture of the product was confirmed by NMR spectra and the average degree of branching (UP) was estimated. Through a comparison of the intrinsic viscosity of the, product with that of its linear analogue, the contraction factor g' was calculated. It Was found that the viscosity of the branched PAN was obviously lower that that of linear PAN. (c) 2008 Wiley Periodicals, Inc.