AFM研究PCL薄膜的结晶形态

THE STUDY ON THE CRYSTAL MORPHOLOGY OF PCL THIN FILMS BY AFM

利用原子力显微镜 (AFM)详细研究了聚己内酯 (PCL)超薄膜及其在特殊限制环境下的结晶形态 .AFM的观察表明 ,PCL在石英基板上的结晶形态呈现典型的球晶及比较少见的树枝状晶两种形态 .认为主要是超薄膜结晶过程中由于几何受限及基板吸附导致分子链扩散移动速度大大降低 ,由此形成的扩散控制结晶过程从而导致最终形成树枝状的分形结构 .将聚合物限制在间距为 10 μm的凹槽内 ,发现PCL的结晶有比较规整的排列 ,而且沿着凹槽的方向结晶排列取向优先 .当在凹槽两侧铝条上施加强电场后 ,发现在静电场作用下 ,PCL的结晶取向生长方向发生改变 。

The crystalline morphology of PCL (poly(epsilon-caprolactone)) thin film was investigated byAFM ( atomic force microscopy). 1% PCL/chloroform solution was spun-cast on different substrates to get thin films. The thickness of the films is about 100 nm. The thin films were annealed at 120degreesC for 48 h, then crystallized at 55degreesC for 72 h. AFM observation showed that two kinds of crystal morphology formed in PCL thin films on polished quartz substrate, i.e. typical spherulite and unusual pinetree branch-like crystal morphologies. It is considered that the diffusion-control crystallizing process results in the formation of the unusual pinetree branch-like crystal morphology while the PCL film is thin enough. It might be the main reason that the interaction between the substrate and the PCL molecules confines the chain diffusion. When the PCL solution was cast on a quartz substrate with designed aluminum grooves of 10 mum wide, it was observed that the crystallites in the PCL thin film exhibited a regular oriented alinement. The orientation along the groove is preponderant. It implies that the crystal first formed from the edges of the aluminum groove and then grew along the groove. When strong electrostatic field is applied to the groove, the PCL crystallization in the thin film exhibited a different morphology, i.e. the crystal arrangement tends to be parallel to the electrostatic field.