Determination of Equilibrium Melting Temperature and Fold Surface Energy for Poly(L-lactic acid) via Simultaneous Small/Wide-angle X-Ray Scattering and Differential Scanning Calorimetry

林逸華(Yi-Hua Lin)

指導教授 ： 蘇安仲

國立清華大學/工學院/化學工程學系/碩士(2010年)

https://doi.org/10.6843/NTHU.2010.00173

摘要

ABSTRACT

By means of synchrotron-based and simultaneous small/wide-angle X-ray scattering and differential scanning calorimetry, we adopted our previously developed method to determine the equilibrium melting temperature (Tmº) and the fold surface energy (σe) of poly(L-lactic acid)(PLLA).With gradually increased temperature, the crystalline lamellae approached solid-melt equilibrium for reliable construction of the Gibbs-Thomson (GT) melting line. In addition, the
lamellar thicknesses were more confidently determined by the arrayed-disks model fitting instead of the previous method of one-dimensional correlation function or Kratky-Porod approximation. From the GT line thus determined, we have obtained Tmº ≈ 199 ºC and σe ≈ 46 mJ m−2. Comparison of the present Tmº and σe values with those previously reported using different approaches are critically
made in terms of consistency between the experimental design and inherent assumptions within each theoretical model. We proposed that the fold surface energy depends on intricacies in the fold structure, which are kinetically determined, generally path-dependent, and subjected to
reorganization before reaching the equilibrium melting line. This explains the wide-range of reported σe values for a given polymer from nucleation, growth, or melting studies and the poor correlation to chain rigidity among different polymers.

關鍵字

左旋聚乳酸 ； 平衡熔點 ； 摺疊表面能 ； 晶板厚度 ； 小角度散射

並列摘要

無資料

並列關鍵字

poly(L-lactic acid) ； equilibrium melting temperature ； fold surface energy ； Gibbs-Thomson melting line ； Simultaneous Small/Wide-angle X-Ray Scattering ； lamellar thickness

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