聚(ε-己内酯)薄膜结晶形貌及分子取向研究

用匀胶机通过溶液铸膜方法在硅片和铝箔基板上分别制备具有不同厚度的聚(ε-己内酯)(PCL)薄膜. 通过原子力显微镜(AFM)和偏光衰减全反射傅里叶红外光谱(ATR-FTIR)对薄膜中PCL的结晶形貌、 片晶生长方式及分子链取向进行了研究. AFM结果表明, 在200 nm或更厚的薄膜中, PCL主要以侧立(edge-on)片晶的方式生长; 对于厚度小于200 nm的薄膜, PCL片晶更倾向于以平躺(flat-on)的方式生长. 这种片晶生长方式的改变在硅片和铝箔基板上都表现出同样的倾向. 此外, 在15 nm或更薄的薄膜中, PCL结晶由通常的球晶结构变为树枝状晶体. 偏光ATR-FTIR结果表明, 当膜厚小于200 nm时, 薄膜结晶中PCL分子链沿垂直于基板表面方向取向, 并且膜越薄, 取向程度越高, 与AFM的观测结果一致.

Crystalline Morphologies and Molecular Orientation of Poly(ε-caprolactone) Thin Films

Crystalline morphologies and molecular orientation of poly(ε-caprolactone)(PCL) thin films were investigated by means of combination of microscopic and spectroscopic methods. The PCL films with different thicknesses were prepared on Si and Al substrate by spin-coating. Atomic force microscopy(AFM) observations reveal that for the PCL films with thickness of ca. 200 nm and thicker than it, crystallization occurs preferentially in the form of edge-on lamellar crystals, whereas for thinner films, nucleated edge-on lamellar crystals become to rotate with some tilt angles, and with further decreasing film thickness, lamellae prefer into the plane of the film and grow as flat-on lamellae, which led to a preferred orientation of the PCL main chain axis perpendicular to the surface of the substrate. In addition, there is a dendritic crystal morphology formed when the film thickness is ca. 15 nm. The mean orientation of the polymer molecules in the  films was measured by polarized ATR-FTIR(attenuated total reflection-Fourier transform infrared) spectroscopy, and the results of the polarized ATR-FTIR  correspond to the AFM observations mentioned above. Those phenomena were discussed under a diffusion-limitation crystallization condition in PCL thin films.