三酰甘油二元混合物形成 POP/OPO、POP/rac-PPO 和 POP/sn-PPO 分子化合物的结晶和转化行为,Crystal Growth & Design

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三酰甘油二元混合物形成 POP/OPO、POP/rac-PPO 和 POP/sn-PPO 分子化合物的结晶和转化行为
Crystal Growth & Design ( IF 3.2 ) Pub Date : 2023-03-15 , DOI: 10.1021/acs.cgd.3c00038
Laura Bayés-García ₁ , Koji Fukao ₂ , Takashi Konishi ₃ , Kiyotaka Sato ₄ , Ken Taguchi ₅

Affiliation

脂基软质材料一般含有不同的三酰甘油（TAG）种类；因此，TAG 混合物的相行为决定了它们重要的物理性质。TAG 二元混合物通常表现出共晶、偏晶、固溶体和分子化合物 (MC) 形成相；其中，控制 MC 相形成过程的分子相互作用和结晶动力学仍未得到探索。我们使用热分析、X 射线衍射和光学显微镜检查了 1,3-二棕榈酰-2-油酰甘油 (POP)/1,3 的三种 MC 形成 1:1 二元 TAG 混合物的结晶和转化动力学-二油酰-2-棕榈酰甘油 (OPO)、POP/1,2-二棕榈酰-2-油酰-rac-甘油 ( rac -PPO) 和 POP/1,2-二棕榈酰-3-油酰-sn-甘油 ( sn -PPO)。在 POP/OPO 混合物中，具有双链长堆叠 (β-2L) 的最稳定 β 形式的MC _{POP/OPO晶体通过简单的冷却处理结晶。}在 POP/ rac -PPO 混合物中，MC _{POP/ rac -PPO}的 β-2L 形式仅通过以 0.1 °C/min 的冷却速度结晶，而亚稳态β' -2L 以 0.5 °C/min 的冷却速度形成和 2.0 °C/分钟；然后β' -2L 在加热过程中熔化并部分转变为 β 形式。POP/ sn -PPO 混合物表现出不同且显着复杂的多晶型行为。首先，单组分sn -PPO 结晶于β'在冷却过程中具有三重链长堆叠 ( β' -3L)。随后以0.1 °C/min 和 0.5 °C/min 的缓慢冷却速率结晶 POP 和 MC _{POP/ sn -PPO}的β' -2L 形式，α-2L 在 2.0 °C/分钟。在加热过程中，亚稳态的β'或α形式熔化，MC _{POP/ sn -PPO}在熔化前转变为β形式。通过光学显微镜观察等温晶体生长速率表明，sn -PPO β-3L 晶体比其他单一 TAG 或 MC 生长得更快，特别是在 ~18 °C 以上。sn -PPO、POP 和 MC之间结晶动力学的差异_{当POP/ sn -PPO}混合物冷却时，POP/ sn -PPO 可能会导致分离结晶。

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Crystallization and Transformation Behavior of Triacylglycerol Binary Mixtures Forming Molecular Compounds of POP/OPO, POP/rac-PPO, and POP/sn-PPO

Fat-based soft materials generally contain different triacylglycerol (TAG) species; hence, TAG mixtures’ phase behaviors determine their important physical properties. TAG binary mixtures typically exhibit eutectic, monotectic, solid solution, and molecular compound (MC) forming phases; among them, the molecular interactions and the crystallization kinetics controlling the formation processes of MC-phases remain unexplored. We used thermal analysis, X-ray diffraction, and optical microscopy to examine the crystallization and transformation kinetics of the three MC-forming 1:1 binary TAG mixtures of 1,3-dipalmitoyl-2-oleoyl glycerol (POP)/1,3-dioleoyl-2-palmitoyl glycerol (OPO), POP/1,2-dipalmitoyl-2-oleoyl-rac-glycerol (rac-PPO), and POP/1,2- dipalmitoyl-3-oleoyl-sn-glycerol (sn-PPO). In the POP/OPO mixture, the MC_POP/OPO crystals of the most stable β form with double chain length stacking (β-2L) were crystallized by simple cooling treatments. In the POP/rac-PPO mixture, the β-2L form of MC_POP/rac-PPO was crystallized by only cooling at 0.1 °C/min, while metastable β′-2L formed at the cooling rates of 0.5 °C/min and 2.0 °C/min; then β′-2L melted and partially transformed into the β form during the heating processes. The POP/sn-PPO mixture showed different and significantly intricate polymorphic behavior. First, a single component of sn-PPO crystallized in β′ with triple chain length stacking (β′-3L) during cooling. This was followed by the crystallization of POP and MC_POP/sn-PPO of the β′-2L forms at slow cooling rates of 0.1 °C/min and 0.5 °C/min, and the α-2L forms at 2.0 °C/min. During heating, the metastable β′ or α forms melted, and MC_POP/sn-PPO transformed into the β form before melting. Observations of isothermal crystal growth rates by optical microscopy revealed that sn-PPO β-3L crystals grow faster than the other single TAGs or MCs, particularly above ∼18 °C. Differences in the crystallization kinetics between sn-PPO, POP, and MC_POP/sn-PPO may cause the separate crystallization while the POP/sn-PPO mixture cools.

更新日期：2023-03-15

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