Synthesis of Star Block Copolymers by Controlled Ring-Opening MetathesisPolymerization

摘要

Living polymers made by adding norbornene to Mo(CH-t-Bu)(NAr)(O-t-Bu)2(NAr = N-2,6-C6H3-i-Pr2) react with 1,3-pentadienes and styrene to yield Mo(CHR)(NAr)(O-t-Bu)2 (R = CH=CHMe or Ph) and methylene capped polynorbornene. Both trans-1,3-pentadiene and styrene were found to be effective chain transfer agents, e.g., treating a mixture of Mo(CH-t-Bu)(NAr)(O-t-bu)2 and styrene (30 eq) at 40 min intervals with 10 portions of 80 eq of norbornene yielded an 80-mer with a PDI of 1.13 overall (1.07 for the main peak, approx. 95% of total). Analogous reactions involving 5,6-bis(trifluoromethyl)norbornadiene as the monomer gave a distribution of low molecular weight oligomers. Keywords: Block copolymers, Metathesis polymerization, Cross linking reagent, Polymers, Polynorbornene, Norbornene. (js)