Synthesis Of Cleavable Multiblock Copolymer Via Ring-Opening Metathesis Polymerization

Grubbs' catalysts are widely applied for the synthesis of well-defined and highly functionalized polymers by ring-opening metathesis polymerization (ROMP) , which has attracted considerable research attention recently in the field of polymer chemistry. Grubbs' catalysts can be used for ring-close metathesis also. In this paper, ring-opening insertion metathesis polymerization (ROIMP) was used to synthesize the multiblock copolymers which can be cleaved into telechelic functional polymers with shortened chain structure under conventional alkaline conditions. The copolymer and the telechelic polymer were characterized by ~1H NMR, GPC, and IR measurements, and the reasults show the synthesized copolymers have the expected multiblock structure.Di- or triblock copolymers have been synthesized via ring-opening metathesis polymerization. But the synthesis of multiblock copolymers have been paid relatively limited attentions because it is still a challenge up to now. It is well-known that ROMP of strained cyclic olefins is mainly enthalpy-driven, whereas macrocyclic olefins (MCOs) are strainless which can undergo entropically driven ring-opening metathesis polymerization (ED-ROMP). In this paper, a novel cleavable multiblock copolymer was synthesized by ring-opening metathesis polymerization (ROMP) of cyclooctene (COE) and a flexible 27-membered macrocyclic olefin (MCO), which is acted as the spacer to collect the polymer structure block by block. MCO 2 was prepared via ring-closing metathesis of the long chain alkyldiene, and then 2 was well conducted ROMP with COE to provide the multiblock copolymer [Poly(COE)-2]_m consisting of homo-Poly(COE) blocks and ring-opened 2 segments with different molecular weights and polydispersity index as variation of the feed ratio of COE to 2. The multiblock copolymer chain containing weak ester linkage can be cleaved under alkali condition to afford the carboxyl-telechelic Poly(COE) blocks with much lower molecular weights. The functional carboxyl group on the telechelic polymer ends can be changed further to anthracene moiety by esterification.