Sung C S, Hu C B, Merrill E W, Salzman E W
J Biomed Mater Res. 1978 Nov;12(6):791-804. doi: 10.1002/jbm.820120603.
During the solvent casting process, one side of the polymer film is exposed to air while the other side is in contact with a substrate, used as a mold. We have studied the effect of this difference in exposure during casting on the chemical composition of two types of segmented polyurethane, Biomer and Avcothane, by using Fourier transform IR internal reflection spectroscopy. Also, a depth-composition profile was obtained by placing a thin barrier film between the reflection plate and the polymer film. In Avcothane, the air side, which is the blood-contact side, contains a greater amount of the soft segment than the substrate side, and this is more pronounced in the layer closer to the surface. The anisotropy in composition is more drastic when the silicone content is compared. In a layer about 1.5 mu thick, one can detect a greater amount of silicone in the substrate side than in the air side. However, when one averages the concentration in a layer of about 0.8 microns the trend in reversed; i.e., the greater amount of silicone is now present in the air side than in the substrate side. In Biomer films, the anisotropy in chemical composition is less pronounced. Only a modest increase in the relative content of the soft segment/hard segment is observed in the air side when a depth-composition profile is obtained.
在溶剂浇铸过程中，聚合物薄膜的一侧暴露于空气中，而另一侧与用作模具的基材接触。我们通过使用傅里叶变换红外内反射光谱法研究了浇铸过程中这种暴露差异对两种嵌段聚氨酯（Biomer和Avcothane）化学成分的影响。此外，通过在反射板和聚合物薄膜之间放置一层薄的阻隔膜获得了深度成分分布。在Avcothane中，作为血液接触侧的空气侧比基材侧含有更多的软段，并且在更靠近表面的层中这种情况更明显。当比较硅氧烷含量时，成分的各向异性更为显著。在约1.5微米厚的层中，可以检测到基材侧的硅氧烷含量比空气侧更多。然而，当对约0.8微米厚的层中的浓度进行平均时，趋势相反；即，现在空气侧的硅氧烷含量比基材侧更多。在Biomer薄膜中，化学成分的各向异性不太明显。当获得深度成分分布时，在空气侧仅观察到软段/硬段相对含量的适度增加。
