Determining order-to-disorder transitions in block copolymer thin films using a self-referencing fluorescent probe,Molecular Systems Design & Engineering

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Determining order-to-disorder transitions in block copolymer thin films using a self-referencing fluorescent probe
Molecular Systems Design & Engineering ( IF 3.2 ) Pub Date : 2019-11-13 , DOI: 10.1039/c9me00091g
Zhe Qiang _{1,

2,

3,

4} , Lingqiao Li _{1,

2,

3,

4} , John M. Torkelson _{1,

2,

3,

4,

5} , Muzhou Wang _{1,

2,

3,

4}

Affiliation

The thin film geometry of block copolymers (BCPs) required by many applications often leads to a shift of their order-to-disorder transition temperature (T_ODT) due to the presence of air–polymer and substrate–polymer interfaces. A challenge associated with measuring BCP thin film T_ODTs is the lack of a simple, generalizable, non-destructive characterization method, which is of critical importance for exploiting BCP self-assembly in nanotechnology. In this work, we present a non-invasive fluorescence characterization method for determining the T_ODT of BCP thin films. Fluorescent pyrene molecules were covalently attached at nearly trace levels to one block and used as a probe of the local polymer matrix. The BCP T_ODT can be determined by a discontinuous change in the intensity ratio I₁/I₃ of pyrenyl vibronic emission bands as a function of temperature, which is induced by a change of the nanoscopic chemical environment around the pyrene labels at the ODT. When the BCP film thickness is sufficiently small, an increase of T_ODT compared to bulk is observed. This increase of T_ODT in thin films is mainly attributed to attractive polymer–substrate interactions, the effects of which can be varied by adjusting the film thickness and substrate surface hydrophobicity. These results not only demonstrate that fluorescence characterization can be used as a generalizable approach for determining BCP thin film ODTs, but also provides additional insights on manipulating functional BCP nanopatterns by controlling the substrate surface functionality.

中文翻译：

使用自参考荧光探针确定嵌段共聚物薄膜中的有序转变

由于存在空气-聚合物和底物-聚合物界面，许多应用所需的嵌段共聚物（BCP）薄膜的几何形状通常会导致其_阶跃转变温度（T _ODT）发生变化。与测量BCP薄膜T _ODT相关的挑战是缺乏一种简单，可推广，无损的表征方法，这对于在纳米技术中利用BCP自组装至关重要。在这项工作中，我们提出了一种非侵入性的荧光表征方法，用于确定BCP薄膜的T _ODT。荧光pyr分子以几乎痕量的水平共价连接到一个嵌段上，并用作局部聚合物基质的探针。BCPT _ODT可以通过pyr基电子发射带的强度比I ₁ / I ₃的不连续变化作为温度的函数来确定，这是由ODT labels标记周围的纳米化学环境的变化引起的。当BCP膜厚度足够小时，观察到T _ODT与体相相比增加。T _ODT的增加薄膜中的杂质主要归因于有吸引力的聚合物-底物相互作用，其作用可通过调节膜厚度和底物表面疏水性来改变。这些结果不仅证明荧光表征可以用作确定BCP薄膜ODT的通用方法，而且还提供了通过控制基板表面功能来操纵功能性BCP纳米图案的更多见解。

更新日期：2019-11-13

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