title: Crystallization-driven surface segregation and surface structures in poly(L-lactide)-block-poly(ethylene glycol) copolymer thick films.
abstract: In this work, we used poly(L-lactide)-block-poly(ethylene glycol) (PLLA-b-PEG) copolymer thick films to investigate the effect of crystallization on surface segregation, surface crystal orientation, and morphology by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), reflection optical microscopy (ROM), and two-dimensional grazing incident wide-angle X-ray scattering (2D GIWAXS) methods. ATR-FTIR results indicated that the surface fraction of PLLA block increased from 0.48 to 0.79 when T(c,PLLA) increased from 70 to 110 °C. Polarized ATR-FTIR and 2D GIWAXS results indicated that PLLA crystal lamellae preferentially oriented parallel to the film surface with increasing T(c,PLLA). The surface crystallinity of PLLA was almost independent of T(c,PLLA), while the surface crystallinity of PEG decreased with increasing T(c,PLLA). On the basis of surface crystal orientation and crystallization kinetics, we suggested that the excess of PLLA component at the surface was mainly dominated by a coupling effect of crystallization behavior and surface segregation.
authors: State Key Laboratory of Polymer Physics and Chemistry, Joint Laboratory of Polymer Science and Materials, The Beijing National Laboratory for Molecular Sciences, and Institute of Chemistry, Chinese Academy of Sciences , Beijing 100080, China.
authors: Jingjing
authors: J
authors: Yang
authors: Yongri
authors: Y
authors: Liang
authors: Charles C
authors: CC
authors: Han
mesh_terms: D003460:Crystallization; D007773:Lactates / Q000737:chemistry*; D015394:Molecular Structure; D010316:Particle Size; D011092:Polyethylene Glycols / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D007773:Lactates; C088513:poly(lactic acid-ethylene glycol); D011092:Polyethylene Glycols