Multilength Scale Studies of the Confined Crystallization in Poly(L-lactide)-block-Poly(ethylene glycol) Copolymer

In this work, we investigated the structure and morphology formation in crystalline crystalline diblock copolymer of poly(L-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) on different length scales with optical microscopy (OM), atomic force microscopy (AFM), synchrotron time-resolved small-angle X-ray scattering (TR-SAXS) and wide-angle X-ray scattering (WAXS) methods. The PLLA-b-PEG copolymer with 5000 of number-average of molecular weight of PLLA and PEG blocks was used in this work. The structure and morphology of PLLA-b-PEG copolymers were formatted by a two-step crystallization process: i.e., the PLLA block crystallized fully at 110 degrees C in the first step, and then the PEG block crystallized fully at 30 degrees C in the second step. The OM, AFM, and SAXS results indicated that the PEG block crystallized in the multilength scales amorphous regions confined by PLLA crystals. The PEG block crystallized not only in the interlamellar regions of PLLA crystals, but also in the interfibrillar regions of PLLA. However, the subsequent crystallization of PEG block did not alter the foregoing spherulitic morphology of PLLA on the micrometer scale.