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[摘要]：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-methylcyclohexylalycolide < rac-lactide. The glass transition temperature of poly(rac-dicyclohexylglycolide) is 98 degrees 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 degrees C, while that of poly(R,R-dicyclohexylglycolide) increased to 104 degrees 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. |
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