Morphology Development in Model Polyethylene via Two-Dimensional Correlation Analysis

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• 作者：Diana S. Smirnova ; Julia A. Kornfield ; David J. Lohse
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：September 13, 2011
• 年：2011
• 卷：44
• 期：17
• 页码：6836-6848
• 全文大小：1309K
• 年卷期：v.44,no.17(September 13, 2011)
• ISSN：1520-5835

文摘

Two-dimensional (2D) correlation analysis is applied to synchrotron X-ray scattering data to characterize morphological regimes during nonisothermal crystallization of a model ethylene copolymer (hydrogenated polybutadiene, HPBD). The 2D correlation patterns highlight relationships among multiple characteristics of structure evolution, particularly the extent to which separate features change simultaneously versus sequentially. By visualizing these relationships during cooling, evidence is obtained for two separate physical processes occurring in what is known as 鈥渋rreversible crystallization鈥?in random ethylene copolymers. Initial growth of primarily lamellae into unconstrained melt (鈥減rimary-irreversible crystallization鈥? is distinguished from subsequent secondary lamellae formation in the constrained, noncrystalline regions between the primary lamellae (鈥渟econdary-irreversible crystallization鈥?. At successively lower temperatures (鈥渞eversible crystallization鈥?, growth of the crystalline reflections is found to occur simultaneously with the change in shape of the amorphous halo, which is inconsistent with the formation of an additional phase. Rather, the synchronous character supports the view that growth of frustrated crystals distorts the adjacent noncrystalline material. Furthermore, heterocorrelation analysis of small-angle and wide-angle X-ray scattering data from the reversible crystallization regime reveals that the size of new crystals is consistent with fringed-micellar structures (9 nm). Thus, 2D correlation analysis provides new insights into morphology development in polymeric systems.