Search

AB diblock copolymers were prepared by sequential ring-opening metathesis polymerization of cyclooctenes catalyzed by a Ru-based Grubbs catalyst. The relatively slow polymerization of cis-3-phenylcyclooct-1-ene (3PC) or cis-cyclooct-2-en-1-yl acetate (3AC) was first carried out and then followed by the faster polymerization of unsubstituted cis-cyclooctene (COE) from the active Ru-alkylidene chain ends. In contrast, simultaneous polymerization of the two monomers provides copolymers with a statistical monomer distribution owing to extensive chain transfer. The resulting poly(3PC-b-COE) and poly(3AC-b-COE) diblock copolymers were subjected to hydrogenation to selectively saturate the backbone alkenes. The consequences of architectural variance between the materials from simultaneous vs. sequential polymerizations are reflected by the contrasting thermal characteristics. [ABSTRACT FROM AUTHOR]

3-Substituted cis-cyclooctenes (3RCOEs, R = methyl, ethyl, hexyl, and phenyl) were synthesized and polymerized, and the polymers therefrom were hydrogenated to prepare model linear low density polyethylene (LLDPE) samples. The ring-opening metathesis polymerization (ROMP) of the 3RCOEs using Grubbs' catalyst proceeded in a regio- and stereoselective manner to afford polyoctenamers [poly(3RCOE)] exhibiting remarkably high head-to-tail regioregularity and high trans-stereoregularity. The overall selectivity increases with the increasing size of the R substituent. Hydrogenation of poly(3RCOE)s afforded precision LLDPEs with R substituents on every eighth backbone carbon. [ABSTRACT FROM AUTHOR]