State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Graduate School of Chinese Academy of Sciences Changchun 130022, People's Republic of China.
Langmuir. 2011 Oct 4;27(19):11973-80. doi: 10.1021/la202379b. Epub 2011 Sep 9.
We have studied the coupling behavior of microphase separation and autophobic dewetting in weakly segregated poly(ε-caprolactone)-block-poly(L-lactide) (PCL-b-PLLA) diblock co-polymer ultrathin films on carbon-coated mica substrates. At temperatures higher than the melting point of the PLLA block, the co-polymer forms a lamellar structure in bulk with a long period of L ∼ 20 nm, as determined using small-angle X-ray scattering. The relaxation procedure of ultrathin films with an initial film thickness of h = 10 nm during annealing has been followed by atomic force microscopy (AFM). In the experimental temperature range (100-140 °C), the co-polymer dewets to an ultrathin film of itself at about 5 nm because of the strong attraction of both blocks with the substrate. Moreover, the dewetting velocity increases with decreasing annealing temperatures. This novel dewetting kinetics can be explained by a competition effect of the composition fluctuation driven by the microphase separation with the dominated dewetting process during the early stage of the annealing process. While dewetting dominates the relaxation procedure and leads to the rupture of the ultrathin films, the composition fluctuation induced by the microphase separation attempts to stabilize them because of the matching of h to the long period (h ∼ 1/2L). The temperature dependence of these two processes leads to this novel relaxation kinetics of co-polymer thin films.
我们研究了微相分离和自憎去湿在弱分离聚（ε-己内酯）-嵌段-聚（L-丙交酯）（PCL-b-PLLA）两嵌段共聚物超薄膜在涂覆碳的云母基底上的耦合行为。在高于 PLLA 嵌段熔点的温度下，共聚物在本体中形成层状结构，其长周期为 L∼20nm，这是通过小角 X 射线散射确定的。原子力显微镜（AFM）跟踪了初始膜厚为 h=10nm 的超薄膜在退火过程中的弛豫过程。在实验温度范围内（100-140°C），由于两个嵌段与基底的强烈吸引力，共聚物在约 5nm 处自身去湿成超薄膜。此外，去湿速度随退火温度的降低而增加。这种新的去湿动力学可以通过由微相分离驱动的组成波动与退火过程早期占主导地位的去湿过程之间的竞争效应来解释。虽然去湿主导了弛豫过程并导致超薄膜的破裂，但由微相分离引起的组成波动由于 h 与长周期（h∼1/2L）匹配而试图稳定它们。这两个过程的温度依赖性导致了共聚物薄膜的这种新型弛豫动力学。
