Phase Behavior and Dimensional Scaling of Symmetric Block Copolymer−Homopolymer Ternary Blends in Thin Films

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• 作者：Guoliang Liu ; Mark P. Stoykovich ; Shengxiang Ji ; Karl O. Stuen ; Gordon S. W. Craig ; Paul F. Nealey
• 刊名：Macromolecules
• 出版年：2009
• 出版时间：April 28, 2009
• 年：2009
• 卷：42
• 期：8
• 页码：3063-3072
• 全文大小：533K
• 年卷期：v.42,no.8(April 28, 2009)
• ISSN：1520-5835

文摘

The phase behavior and dimensional scaling of symmetric ternary blends composed of poly(styrene-block-methyl methacrylate) block copolymers and the corresponding polystyrene and poly(methyl methacrylate) homopolymers in thin films were investigated as a function of χN (the product of the Flory−Huggins interaction parameter and the overall degree of polymerization of the block copolymer), α (the ratio of the degree of polymerization of the homopolymers to that of the block copolymer), and <sub>Hsub> (the volume fraction of homopolymers in the blends). The phase transitions were characterized by three methods: disappearance of high-order peaks in the fast Fourier transform (FFT) spectra from scanning electron microscopy (SEM) images, application of the amphiphilicity factor determined from the FFTs, and, in the case of thicker films, the appearance of either microphase- or macrophase-separated domains in SEM images. Above the order−disorder transition (ODT) in the χN−<sub>Hsub> phase diagram, the symmetric ternary blends transitioned from lamellae to a microemulsion and then to macrophase-separated domains as <sub>Hsub> increased. The phase transitions depended weakly on χN and α in the range of 12.7 ≤ χN ≤ 36.7 and 0.20 ≤ α ≤ 0.99. The periods of swollen lamellae and microemulsions (L<sub>Bsub>) were determined as a function of <sub>Hsub> and α and were well described empirically with L<sub>Bsub> = L<sub>0sub>/(1 − <sub>Hsub>)<sup>βsup>, where L<sub>0sub> is the natural period of pure block copolymer and β is a parameter that depends linearly on α with values ranging from 0.5 to 1.5.