Catalytic synthesis and post-polymerization functionalization of conjugated polyisoprene

Anionically synthesized polyisoprene (PI) was catalytically isomerized with RuHCl(CO)(PPh₃)₃ to produce conjugated PI (CPI). Both the reaction time and temperature were varied to control the number of conjugated dienes along the CPI backbone. The same reaction scheme also conjugated polycyclooctadiene, demonstrating the utility of the catalyst to conjugate other olefin-containing polymers. The CPI samples retained their narrow distributions as indicated by size exclusion chromatography (SEC). Small molecules were coupled with CPI through the Diels-Alder click reaction in solution to produce an array of post-polymerization functionalized polymers. In one example, N-2-hydroxyethyl maleimide (HEMI) was coupled to CPI to produce a hydroxylated material. l-Lactide was polymerized from this macroinitiator with both tin(ii) octoate (Sn(Oct)₂) and 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) to produce poly(l-lactide) (PLLA) grafted from PI (PI-g-PLLA) with a monomodal SEC distribution at 95 wt% PLLA content.