Arceo Abraham, Green Peter F
Department of Chemical Engineering and Texas Material Institute, The University of Texas at Austin, Austin, Texas 78712, USA.
J Phys Chem B. 2005 Apr 21;109(15):6958-62. doi: 10.1021/jp050636i.
It is well-known that a bulk, symmetric, A-b-B diblock copolymer forms a lamellar morphology, with period L, below an order-disorder transition (T(ODT)) temperature, for chiN < 10.5; chi is the Flory-Huggins interaction parameter and N is the degree of polymerization of the copolymer. The ordering temperatures of poly(styrene-b-methyl methacrylate) (PS-b-PMMA) thin film diblock copolymers of thickness h </= 2L, supported by SiO(x)/Si substrates, in vacuum environments, are shown to increase beyond the bulk, and estimates of the temperature shifts indicate that small changes of chiN are associated with unusually large shifts of the transition temperature. Further, we find that in compressed CO(2) environments, these films are ordered at temperatures where the films are disordered in vacuum (or air) environments. This latter observation is of particular significance because small molecule diluents, including compressed CO(2), are known to decrease the ODT of the bulk (enhanced miscibility).
众所周知，对于χN < 10.5，在有序-无序转变（T(ODT)）温度以下，本体对称的A-b-B二嵌段共聚物会形成周期为L的层状形态；χ是弗洛里-哈金斯相互作用参数，N是共聚物的聚合度。在真空环境中，由SiO(x)/Si衬底支撑的厚度h ≤ 2L的聚（苯乙烯-b-甲基丙烯酸甲酯）（PS-b-PMMA）薄膜二嵌段共聚物的有序温度显示高于本体，并且温度变化的估计表明χN的小变化与转变温度的异常大变化相关。此外，我们发现，在压缩CO₂环境中，这些薄膜在真空（或空气）环境中无序的温度下是有序的。后一观察结果具有特别重要的意义，因为已知包括压缩CO₂在内的小分子稀释剂会降低本体的ODT（增强混溶性）。
