**4.2. Copolymerization**

Modification in the synthesis process with other monomers is other way to tune the properties of polylactides. Comonomers as etylenglycol or ethylene oxide [49, 50], propylene oxide [51] and trimethylcarbonate [52] have been reported for polymerization with lactide units. However, cyclic comonomers are suitable to polymerize by ring opening polymerization (ROP) with lactide such as lactones or macrolactones. The most investigated systems are poly(glycolide‐lactide) [53, 54] and poly(lactide‐co‐caprolactone) copolymers [55–57]. Recent‐ ly, some studies in search of more biodegradable copolymers are using macrolactones as γ‐ valerolactone [58].

Moreover, starting the polymerization of lactide or lactic acid with polymer containing hydroxyl groups leads into graft copolymers. This strategy is welcomed to increase the miscibility with other polymers and hydrophobicity as it occurs with poly(vinyl alcohol) [59].
