Cyclohexyl-Substituted Polyglycolides with High Glass Transition Temperatures

The substituted glycolides rac -dicyclohexylglycolide ( rac -3,6-dicyclohexyl-1,4-dioxane-2,5-dione), meso -dicyclohexylglycolide, R, R -dicyclohexylglycolide, and rac -methylcyclohexylglycolide ( rac -3-cyclohexyl-6-methyl-1,4-dioxane-2,5-dione) have been synthesized, and both solution and bulk polymerizations of these monomers are reported. The polymerization kinetics of these new monomers were studied and compared to data for rac -diisopropylglycolide ( rac -3,6-diisopropyl-1,4-dioxane-2,5-dione) and rac -lactide. The solution polymerization rates followed the order: rac -dicyclohexylglycolide < rac -diisopropylglycolide < rac -methylcyclohexylglycolide < rac -lactide. The glass transition temperature of poly( rac -dicyclohexylglycolide) is 98 °C, consistent with a stiff polyglycolide backbone. meso -Dicyclohexylglycolide and R, R -dicyclohexylglycolide were synthesized and polymerized to study the effect of stereochemistry on the polymer properties. The glass transition temperature of meso -dicyclohexylglycolide was 96 °C, while that of poly( R, R -dicyclohexylglycolide) increased to 104 °C. While NMR spectroscopy indicated that poly( R, R -dicyclohexylglycolide) undergoes minimal racemization during polymerization, differential scanning calorimetry (DSC), X-ray diffraction (XRD), and polarized optical microscopy confirmed that the polymer was amorphous.