**4.1. Blending**

Easier strategy to change properties of a pure polymer is blending with other polymers. These blends could be miscible or immiscible depending on solubility parameters and specific interactions established between counterparts. Miscibility of blends is governed by thermo‐ dynamic law, in which the free energy of mixing in the blend must be negative [30]. Polylactide is miscible with polyvinylphenol (PVPh) [36–39], poly(styrene‐co‐vinylphenol) [40, 41], polyhydroxybutirate (PHB) [42], poly(methyl methacrylate) (PMMA) [43], poly(vinyl acetate) [44] and poly(ethylene oxide) [45].

Phase separation induced by immiscible blends has been commonly used for improving fragile commodity polymers as PS and PMMA with a rubber modification leading into HIPS [46] and high impact PMMA [47]. However, the modifications in polylactides with biodegradable polymers as polycaprolactone (PCL) are an efficient way to toughen polylactides [48].
