膜厚对PLLA-b-PEG嵌段共聚物结晶的影响

Effect of Film Thickness on the Crystallization Behavior of Poly(L-Lactide)-Block-Poly(Ethylene Glycol)Diblock Copolymer

为研究膜厚对左旋聚乳酸-聚乙二醇两嵌段共聚物结晶行为的影响，通过旋徐法制备了437～30nm厚度范围的一系列薄膜样品．利用反射光学显微镜、原子力显微镜以及二维掠入射广角X射线散射等手段对薄膜样品的结晶形貌、结晶行为以及结晶取向进行了分析．嵌段共聚物薄膜样品在70℃等温结晶的显微镜结果表明：当膜厚为50nm时，样品具有最大的晶体生长速率，约为18．3μm·min-1；当薄膜厚度低于90nm时，PLLA嵌段的结晶形貌从球晶转化为分形的树枝状结晶；当薄膜厚度为437nm与330nm时，PLLA嵌段的结晶为无规取向，表现出各向同性；当薄膜厚度小于90nm时，PLLA嵌段的结晶取向倾向于flat—on取向，最终构成多层片晶堆积的树枝形貌．

Effect of film thickness on the crystallization behavior poly（L-lactide）-block-poly（ethylene glycol） diblock copolymer was investigated. Films with thickness of 30 nm-437 nm were prepared by spin-coating. Using reflection optical microscopy （ROM）, atomic force microscopy （AFM） and two- dimensional grazing incident wide angle X-ray scattering （2D GIWAXS）, the crystalline morphology, crystallization behavior and crystal orientation of PLLA blocks were analyzed. Poly（L-lactide）-block-poly （ethylene glycol） diblock copolymer samples with different film thickness were isothermally crystallized at 70 ℃. Results demonstrated that the film with 50 nm thickness gave a maximum grystal growth rate of about 18. 3 μm min-1. When film thickness was less than 90 nm, the crystalline morphology of PLLA blocks changed from spherulites like morphology to dendrite. When film thickness was 437 and 330 nm, lamellar orientation of PLLA blocks was random and isotropic; While in samples with film thickness less than 90 nm,PLLA blocks gave flat-on lamellar orientation and the flat-on lamellar formed the final multilayer dendrite morphology.