A polylactide copolymer comprises a graft copolymer of a hydrophobic backbone polymer having a plurality of pendant hydroxyl groups and lactide. In one example, a polylactide includes a graft copolymer of a poly(1,5-cyclooctadiene-co5-norbornene-2-methanol) copolymer and lactide. A method of preparing a toughened polylactide comprises forming a hydrophobic backbone copolymer having a plurality of pendant hydroxyl groups and forming a polylactide graft copolymer by reacting the hydrophobic backbone copolymer having a plurality of pendant hydroxyl groups with lactide, wherein polymerized lactide stems from at least one of the plurality of pendant hydroxyl groups. In one example, a method comprises forming poly(1,5-cyclooctadiene-co-5-norbornene-2-menthanol) by reacting 1,5-cyclooctadiene and 5-norbornene-2-methanol in the presence of a 2nd generation Grubbs' catalyst and cis-1,4-diacetoxy-2-butene as a chain transfer agent and forming poly(1,5-cyclooctadiene-co-5-norbornene-2-methanol-graft-lactide) by reacting the poly(1,5-cyclooctadiene-co-5-norbornene-2-menthanol) as a macroinitiator with lactide in the presence of tin 2-ethylhexanoate and toluene or in the presence of 1,5,7-triazabicyclo[4.4.0]dec-5-ene and dichloromethane.