Immiscible poly(L-lactide)/poly(ε-caprolactone) blends:: Influence of the addition of a poly(L-lactide) -poly(oxyethylene) block copolymer on thermal behavior and morphology

A binary blend of poly (L-lactide) (PLLA) and poly(epsilon-caprolactone) (PCL) of composition 70:30 by weight was prepared using a twin screw miniextruder and investigated by differential scanning calorimetry (DSC), optical microscopy and scanning electron microscopy (SEM). Ternary 70:30:2 blends were also obtained by adding either a diblock copolymer of PLLA and poly(oxyethylene) (PEO) or a triblock PLLA-PCL-PLLA copolymer as a third component. Optical microscopy revealed that the domain size of dispersed PCL domains is reduced by one order of magnitude in the presence of both copolymers. SEM confirmed the strong reduction in particle size upon the addition of the copolymers, with an indication of an enhanced emulsifying effect in the case of the PLLA-PEO copolymer. These results are analyzed on the basis of solubility parameters of the blend components.