Knotted ring polystyrene (PS) with molecular weight of 380 k was successfully synthesized by intramolecular cyclization reaction in cyclohexane under extremely diluted condition. Crude product was confirmed to include linear precursor molecule, single ring molecules, and various intermolecular-reacted byproducts by SEC and interaction chromatography characterizations. The crude product was fractionated repeatedly several times by high performance interaction chromatography and finally highly-purified knotted ring molecules were obtained. It has been found by SEC-MALS that the chain dimension of the knotted ring polymers is evidently smaller than those of linear and the trivial ring polymer, while knotted polymer molecules have the same absolute molecular weight as the corresponding counterparts. (C) 2011 Elsevier Ltd. All rights reserved.