本研究利用偏光顯微鏡(POM)、電子顯微鏡(SEM)以及原子力顯微鏡(AFM) 探討有機小分子鄰苯二甲酸(phthalic acid, PA)分別與半結晶性高分子聚氧化乙烯(poly(ethylene oxide), PEO)或具有多個酚基的天然高分子單寧酸(tannic acid, TA)混摻系統之結晶行為。在 PA/PEO 混摻系統中，發現當PEO的組成比例大於20 wt.%時，首次觀察到新穎的分形環帶狀球晶(fractal-shape banded spherulite)，且隨著PEO含量提升，其環帶間距亦趨增大。推測稀釋劑PEO的添加是將晶體形態從緊密帶狀圖案轉變為分形環帶狀圖案的主要因素。在蝕刻掉PEO之後，對其晶板排列方式進行分析，可以發現不同於傳統在高分子系統中觀察到的環帶狀球晶，分形環帶狀球晶是由許多重複單位向外不斷形成分枝所組成。每個分形單元都包含兩個部分：沿著徑向排列的晶體聚集體組成的主幹(main stalk)，以及沿著切線方向排列的離散晶體所組成的蕨狀枝晶(fernlike dendrite)。晶體聚集體的周期性垂直交叉形成帶狀球晶的對比雙折射帶。此外，透過記錄其生長過程證實了形成特殊的分形帶狀球晶的分形-分支生長機制。在 PA/TA 混摻系統中，固定組成比例為PA/TA (80/20)，透過改變揮發溫度誘導產生多樣化的結晶形貌。發現隨著蒸發速率的增加，PA晶體的形貌從環狀球晶系統性地變為有序的柵狀圖案。此外，令人驚訝的是，在中等蒸發速率下可以發現具有對比雙折射帶的獨特周期性分形-分支帶狀圖案，這在其他帶狀球晶中從未發現過。藉由本研究中分析分形-分支組裝在帶狀圖案中的詳細生長機制，可以更加了解分枝結構與週期性帶狀圖案有密不可分的關聯性。

A small-molecular compound, phthalic acid (PA), was crystallized in the presence of poly(ethylene oxide) (PEO) or tannic acid with various compositions to investigate the morphology and crystal assembly of periodically ordered structures of PA banded spherulites.
A novel banded spherulite with fractal-shape lamellar structures could be found in PA/PEO blend when the composition of PEO is above 20%. The addition of diluent PEO was regarded as the main factor to transform crystalline morphology from compact banded pattern to fractal-shape banded pattern. After etching off PEO, detailed crystal assembly was analyzed to reveal the mechanisms of the formation of the fractal-shape banded spherulites. The fractal-shape banded spherulites are composed of numerous of fractal structures periodically branching out. Every fractal unit contains two portions: main stalk (ridge) where discrete crystalline aggregations are arranged along the radial direction, and fernlike dendrite (valley) where crystals are arranged along tangential direction. The periodically perpendicular intersection of discrete crystals results in the contrasted birefringent bands of banded spherulites. In addition, in-situ monitoring of the growth process of the fractal-shape banded spherulite proves the fractal-branching growth mechanism for the formation of banded spherulites. A novel periodically fractal branching leads to such a novel pattern of banded PA spherulite, which cannot be attributed to the classical models of continuous twist lamellae as the small-molecules PA does not chain-fold in lamellae at all.
In PA/TA blend system, PA was crystallized in the presence of strongly interacting tannic acid (TA) to investigate crystal assembly and the correlation between banded pattern and branching structure. Several compositions of the mixture of ethanol/water solutions and evaporation temperatures were also manipulated to investigate the kinetic effects on the morphology of PA crystals. With increasing the evaporation rate, the morphology of PA crystals systematically changes from ring-banded spherulites to highly ordered grating patterns. Surprisingly, a unique periodic fractal-branch banded pattern with contrasted birefringent bands can be found at intermediate evaporation rate, which has never been found in other banded spherulites. Crystal assembly of these three morphologies was analyzed by utilizing atomic-force microscopy (AFM) and scanning electron microscopy (SEM) to reveal the mechanisms of the formation of hierarchical structures of PA. The detailed growth mechanisms of the novel fractal-branching assembly into banded patterns are analyzed in this work.

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