Study of the Compatibility of Polymer Chains in the Two Dimensions

我们用表面压力测量和椭偏仪技术研究了分散在空气/水界面上的二元混合高分子链的结构和相容性。我们选择了四种不同的聚合物：聚环氧乙烷(PEO)、聚丙烯酸甲酯(PMA)、聚乙酸乙烯酯(PVAc)和聚甲基丙烯酸甲酯(P-MMA)。所有聚合物都能在空气-水界面形成稳定的膜。从聚合物膜在恒定表面压力下的实验平均面积随膜中某一组分的摩尔分数变化的曲线图来看，PEO/PMMA混合物和PMA/PVAc混合物在整个组成上是相容的。对于PVAc/PEO混合物，它们在PEO的崩塌表面压力下是相容的。在PVAc/PMMA混合物中，混合物在热力学上不稳定，不应相容。这些结果与相应混合物在体相状态下的相容性很好地关联。椭偏测量结果表明，在较高的表面浓度下，PEO/PMMA混合层在空气-水界面的吸附厚度不超过2.5 nm，与混合物的组成无关。这种薄层厚度似乎是由PEO和PMMA的单个薄膜的平坦构象决定的。PMA/PVA共混物的吸附层厚度随表面浓度的增加而增加，并达到平台值。平台层厚度可达15 nm，与纯PVAc厚度基本相同。

We have studied the structures and compatibility of binary mixed polymer chains spread at the air/water interface using the techniques of surface pressure measurements and ellipsometry. We chose four different polymers such as poly (ethylene oxide)(PEO), poly (methyl acrylate) (PMA), poly (vinyl acetate) (PVAc), and poly (methyl methacrylate) (P-MMA). All polymers lead to a stable film spread at the air-water interface.1. From the plots of the experimental mean area of the mixed polymer films at a constant surface pressure as a function of the mole fraction of one component in the films, PEO/PMMA mixtures and PMA/PVAc mixtures are compatible in their entire composition. For PVAc/PEO mixtures, they are compatible below the collapse surface pressure of PEO. In PVAc/PMMA mixtures, the mixtures are thermodynamically unstable and should not be compatible. These results correlate well with the compatibility of the corresponding mixtures in the bulk state.2. Ellipsometry showed that the thickness of the PEO/PMMA mixture layer adsorbed on the air-water interface at the high surface concentration does not exceed 2.5 nm, independent of composition in the mixtures. This thin layer thickness seems to be governed by the flat conformation of the individual film for PEO and PMMA. On the other hand, the thickness of the adsorbed layer for the PMA/PVA mixtures gives an increase with the surface concentration and reaches a plateau value. The plateau thickness attains to 15nm and its value is almost the same as the pure PVAc thickness.