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.
Langmuir. 2014 Jan 14;30(1):394-401. doi: 10.1021/la4041387. Epub 2013 Dec 23.
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.
在这项工作中，我们使用聚（L-丙交酯）-嵌段-聚（乙二醇）（PLLA-b-PEG）共聚物厚膜，通过衰减全反射傅里叶变换红外光谱（ATR-FTIR）、反射光学显微镜（ROM）和二维掠入射广角 X 射线散射（2D GIWAXS）方法研究了结晶对表面分相、表面晶体取向和形态的影响。ATR-FTIR 结果表明，当 T(c,PLLA)从 70°C 增加到 110°C 时，PLLA 嵌段的表面分数从 0.48 增加到 0.79。偏光 ATR-FTIR 和 2D GIWAXS 结果表明，随着 T(c,PLLA)的增加，PLLA 晶体片层优先沿膜表面取向。PLLA 的表面结晶度几乎与 T(c,PLLA)无关，而 PEG 的表面结晶度随 T(c,PLLA)的增加而降低。基于表面晶体取向和结晶动力学，我们认为表面过量的 PLLA 成分主要由结晶行为和表面分相的耦合效应决定。
