期刊
MACROMOLECULES
卷 50, 期 11, 页码 4406-4414出版社
AMER CHEMICAL SOC
DOI: 10.1021/acs.macromol.7b00357
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资金
- USA National Science Foundation [DMR 1607786]
- Direct For Mathematical & Physical Scien
- Division Of Materials Research [1607786] Funding Source: National Science Foundation
Aiming to understand the inversion of crystallization kinetics observed by DSC, detailed SANS investigations of the melt structure of a broadly distributed ethylene-l-hexene copolymer have been undertaken in a wide range of temperatures that were reached either by heating the solid or cooling from the homogeneous melt state. In both cases, the observed SANS signal transitions from a scattering cross section consistent with a homogeneous melt state (high temperature range) to an intensity that in the low Q region displays the characteristics of the Porod region for particles dispersed in a homogeneous matrix (low melt temperature range). The latter structure is consistent with demixing of the highly branched molecules and corroborates the postulated liquid-liquid phase separation (LLPS) as an explanation for the peculiar crystallization kinetics observed by DSC. The solution temperature is found at 160 degrees C by heating the solid and at 150 degrees C when cooling from the one-phase melt, thus denoting the effect of copolymer crystallization assisting LLPS kinetics. Irrespective of the path taken to approach the melt, SANS gives evidence of the liquid-liquid phase transition while crystallization by DSC is only sensitive to LLPS when cooling from self-nucleated melts.
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