High Tg Aliphatic Polyesters by the Polymerization of Spirolactide Derivatives
Fiore, G. L.; Jing, F.; Young, V. G., Jr.; Cramer, C. J.; Hillmyer, M. A.
Polym. Chem. 2010, 1, 870. (doi:10.1039/C0PY00029A).
A series of bicyclic and tricyclic lactide derivatives was prepared using L-lactide as the starting material. Exomethylene-lactide served as a platform for the Diels-Alder addition of various dienes to afford norbornene-, cyclohexadiene-, and isoprene-lactide derivatives. Norbornene- lactide (NL) was also hydrogenated to the saturated norbornane analog. These new lactide derivatives were subjected to ring-opening polymerization using 1,5,7-triazabicyclo[4.4.0]dec-5- ene (TBD) as the catalyst. Homopolymers of poly(cyclohexadiene-lactide) (Mn = 6.4 kg/mol), poly(isoprene-lactide) (Mn = 15.3 kg/mol), and poly(norbornane-lactide) (Mn = 34.4 kg/mol) exhibited glass transition temperatures (Tg's) of 119 oC, 77 oC, and 107 oC, respectively. The decomposition temperature (Td) of unsaturated PLA derivatives was less than or equal to 280 oC, whereas saturated poly(norbornane-lactide) has a Td of 300 oC. Additionally, a series of poly(norbornene-lactide-s- L-lactide) (P(NL-s-L)) copolymers with varying ratios of NL and L-lactide were prepared. The Tg's of the P(NL-s-L) samples ranged from 61 to 100 oC, and the values were well-described by the Fox equation.