High T_g 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) (M_n = 6.4 kg/mol), poly(isoprene-lactide) (M_n = 15.3 kg/mol), and poly(norbornane-lactide) (M_n = 34.4 kg/mol) exhibited glass transition temperatures (T_g's) of 119 ^oC, 77 ^oC, and 107 ^oC, respectively. The decomposition temperature (T_d) of unsaturated PLA derivatives was less than or equal to 280 ^oC, whereas saturated poly(norbornane-lactide) has a T_d 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 T_g's of the P(NL-s-L) samples ranged from 61 to 100 ^oC, and the values were well-described by the Fox equation.