Morfología y cristalización de copolímeros dibloque a base de polilactide y polietileno con uno o ambos bloques cristalizables

In this work, the crystallization of PE-b-PLDA (polyethylene-b-poly(L,D- lactide) and PE-b-PLLA (polyethyleneb-poly(L-lactide) diblock copolymers of symetric composition was studied. Both systems turned out to be strongly segregated within lamellar nanodomains in the melt. Therefore, the crystallization proceeds within the pre-established lamellae. It was found that the crystallization behavior of the blocks strongly depends on the thermal history. The chain orientation within the crystals formed was determined by wide and low angle X-ray diffraction experiments in three dimensions (the sample was previously shear oriented in the melt). The preferential orientation of the PLLA chains was found to be perpendicular to the lamellar microdomains while that of PE was parallel. This system is the first reported in the literature where orthogonal molecular chain orientation of the constituent blocks is found.