Coordination polymerization of renewable butyrolactone-based vinyl monomers by lanthanide and early metal catalysts

This contribution reports the first study of coordination-addition polymerization of renewable butyrolactone-based vinyl monomers, MBL (alpha-methylene-gamma-butyrolactone) and MMBL (gamma-methyl-alpha-methylene-gamma-butyrolactone), using neutral lanthanocene(II), non-lanthanocene(III), and cationic group 4 metallocene catalysts. The samarocene(II) catalyst, Cp*(2)Sm(THF)(2), promotes a rapid, efficient, and controlled polymerization of MBL and MMBL in DMF at ambient temperature, exhibiting a high TOF of 3000 h(-1), typically near quantitative initiator efficiency, and the ability to control the polymer MW. The resulting atactic PMBL and PMMBL have high T(g)'s of 194 degrees C and 227 degrees C, respectively; when compared to atactic PMMA having comparable MW, the T(g) and onset decomposition temperatures of the PMMBL produced are substantially higher (by approximately 120 degrees C and 40 degrees C, respectively). Owing to the living/controlled characteristics of this polymerization, well-defined random and block copolymers of MBL with MMA and MMBL can be readily synthesized. Results of the kinetic and polymerization studies indicate that the true active species is the trivalent samarocene centers attached to the single growing polymer chain, derived presumably from a redox-then-radical-coupling process. In comparison, the polymerizations by non-lanthanocene(III) silylamides, Ln[N(SiMe(3))(2)](3) (Ln = La, Nd, Sm, Er), and by cationic group 4 metallocene and half-metallocene catalysts incorporating C(2) and C(s) symmetric ligands are much slower and less effective. Catalytic polymerization of MBL by Cp*(2)Sm(THF)(2) has also been realized in the presence of an enolizable organo acid as a suitable chain transfer agent.