In this paper, we report two simple and effective bromination methods to brominate the cyclo olefin copolymer (COC). A suitable metallic catalyst can accomplish functionalization and chromophorization of the brominated COC. A 2nd NLO dye, Disperse Orange 3(DO3) containing the -NH2 functional group, has been grafted onto either the norbornene unit or the PE segment of the COC backbone successfully, by the palladium catalyst, Pd2(dba)2(Bis[dibenzylideneacetone] dipalladium). The observed low dye grafting content can be attributed to the higher hindrance of the norbornene ring. Based on UV results, the NLO-COC, having dye grafted onto the norbornene unit shows more red shift than that grafted onto the PE unit, probably due to greater shielding on the chromorphor. (C) 2000 Elsevier Science Ltd. All rights reserved.