Efficient polymerization of norbornene macromonomer bearing a ring-opened poly(norbornene) substituent has been accomplished by the ring-opening metathesis polymerization by the well-defined Schrock-type molybdenum initiator, Mo(CHCMe2Ph)(N-2,6-(Pr2C6H3)-Pr-i)(OCMe(CF3)(2)). The key steps for the macromonomer synthesis are: (i) selective end capping of ring-opened poly(norbornene) with p-Me3SiOC6H4CHO; (ii) exclusive hydrolysis of the SiMe3 group; and (iii) esterification of OH group produced at the end of preformed polymer chain with norbornene carboxylic acid chloride. Mo(CHCMe2Ph)(N-2,6-(Pr2C6H3)-Pr-i)(OCMe(CF3)(2)) was found to be an effective initiator in order for this polymerization to proceed to the complete conversion. (C) 2000 Elsevier Science Ltd. All rights reserved.