Well-defined polyacrylonitrile (PAN) of high viscosity-average molecular weight (M= 405,100 g/mol) was successfully synthesized using reversible addition-fragmentation chain transfer polymerization. The polymerization exhibits controlled characters: molecular weights of the resultant PANs increasing approximately linearly with monomer conversion and keeping narrow molecular weight distributions. The addition of 0.01 equiv (relative to monomer acrylonitrile) of Lewis acid AlCl3 in the polymerization system afforded the obtained PAN with an improved isotacticity (by 8%). In addition, the influence of molecular weights and molecular weight distributions of PANs on the morphology of the electrospun fibers was investigated. The results showed that, under the same conditions of electrospinning, average diameter (2471094 nm) of fibers increased with molecular weights of PANs, and it was much easier to get uniform diameter fibers while using PANs with narrow molecular weight distributions as the precursor of electrospinning. (c) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013