工程塑膠因其具有高強度、耐衝擊性、耐熱、抗老化及重量輕等優異的特性，符合應用產品朝向輕量、節能、環保等議題的發展，因此工程塑膠已成為現今全球塑膠產業發展中成長最快速的材料，因此開發具優異特性的工程塑膠，已是全球產學界共同研究開發的目標。本研究透過分子結構設計、聚合與改質技術並搭配精密加工製膜技術，去探討雙軸延伸PET膜(BOPET film)的熱穩定性、光學特性、耐水解性，以及液晶高分子膜(LCP film)的耐熱性、機械強度及介電性質與內部微結構的關係，包括:晶體順向性與空間排列特徵、微米尺度之特徵超結構、晶體成核密度、晶板厚度與球晶尺寸、非結晶區之分子排列特性、結晶熱力學參數（熔點、結晶度）、及結晶動力學參數（成核速率與晶體成長速率）等。藉由此研究建立分子設計、製膜加工與結構控制的準則，了解結構與薄膜性質間的關連性。
我們透過雙軸延伸加工製膜製程條件對PET結晶微結構之影響進行探討，研究發現拉伸製程中的延伸倍率可影響shish結構於MD及TD方向的含量，而熱定型溫度與時間則可決定kebab晶體的取向性、晶層厚度及額外球晶生成的含量。另一方面在晶體結構與光學性質的關聯性研究上，也發現當熱定型溫度提升(晶體取向性提高)應有助於薄膜光學性質之提升。
再進一步於線型PET高分子中導入均苯三甲酸(Trimesic acid，TMA)單體製備支鏈型PET，並透過結晶動力學去研究支鏈型PET(B-PET)材料對結晶行為之影響，發現隨著branch單體含量增加，PET冷結晶與熔融結晶的結晶速率下降，但從SAXS分析中卻發現B-PET會形成較厚的層狀晶體堆疊，於是我們透過Thomson-Gibbs及Hoffman-Weeks方程式去計算平衡熔點，發現隨著branch比例增加B-PET的平衡熔點會下降，表示過冷程度(undercooling)變小而減少結晶所需的驅動力，所以可使層狀晶體堆疊厚度增加。進一步我們也發現導入branch單體確實會降低PET晶體的結晶排列規則度，是由於branch單體的導入會降低高分子鏈受力延伸排列方向的規則度，且也會限制部分高分子鏈運動使結晶度降低。接著探討雙軸延伸B-PET膜的耐水解性及尺寸安定性，發現隨著branch單體添加，可有效提薄膜耐水解及尺寸安定性。
接著我們透過聚縮合反應合成更高耐熱的線型LCP高分子，並以WAXD分析探討熱處理(Heat set)製程對不同黏度(IV)的LCP薄膜微結構及耐熱性之影響，從實驗中我們也證實了透過熱處理製程可使LCP薄膜內微結構產生晶體相轉現象，可從較不規則之Hexagonal晶體型態轉變成較規則的Orthorhombic晶體型態，據此提升LCP薄膜耐熱性(熔點可提升約40℃)。在本研究中也發現了隨著黏度的提升可快速提升薄膜耐熱性，但當黏度過小(IV=4.18)並無法透過Heat set製程提升LCP薄膜之耐熱性，推測LCP分子鏈段需達到一定的長度，才能形成Orthorhombic晶體型態，進而提升薄膜耐熱性。
為改善LCP高分子不易製膜加工的流變型態(易順向、熔體黏度低及固化太快等)，透過分子結構設計及聚縮合反應導入TMA單體合成支鏈型LCP高分子材料，在本研究中發現此材料具有高耐熱、高尺寸安定性、優異的機械性能及良好的色澤。進一步解析其流變行為，發現透過branch單體添加，可大幅提升材料熔融強度，延展性及具entanglement的流變性，使其適用於加工製膜製程。將材料製備成LCP薄膜後，展現出低介電常數(Dk)、低介電損耗(Df)、低熱膨脹係數及低吸濕性的傑出性質，可符合5G高頻/高速傳輸用軟性銅箔基板(FCCL)之需求。

Having extraordinary properties like high mechanical strength, impact resistance, and heat resistance, as well as anti-aging and light-weight, engineering plastics have become the fastest growing material in plastic industry for a broad range of applications. The development of engineering plastic with extremely outstanding properties is still a challenging task which requires delicate control of the crystalline structures at various length scales. This thesis is dedicated to establishing the relationship between the properties and structures of engineering polymers, where the microstructures including crystal orientation, nano-scale structure, nucleation density, crystallite thickness and spherulite size were characterized. Moreoever, the thermodynamics and kinetics of crystallization were also explored. The polymer systems studied were biaxially-oriented PET and liquid crystalline polymer (LCP). The objective of this study is to set up the principles of molecular design, film processing and structure-controlling factors for elucidating the correlation between the microstructure and film properties
The effect of biaxial stretching process conditions on the crystalline microstructure of PET was investigated first. It is found that the stretching amount in the process would affect the amount distribution of shish structure among MD and TD directions and both the processing time and temperature could dominate the orientation of kebab crystalline, crystalline thickness and generate more spherulite during thermal setting process. Besides, according to the correlation between the crystalline structure and optical properties observed in this study, it was presumed that the rising the thermal setting temperature would increase the crystalline orientation and thus improve the optical performance of thin film.
We further introduced the trimesic acid (TMA) into the molecular structure of linear PET polymer, and studied the effect of branched molecular structure on the crystallization behavior through crystallization dynamics. It is observed that both thermal and cold crystallization rate decreases when increasing the amount of branched monomer and the branched PET (B-PET) would induce a thicker lamellae crystal which is monitored by means of small angle X-ray scattering (SAXS). Through studying the equilibrium melting point of B-PET calculated by Thomson-Gibbs and Hoffman-Weeks equations, it is found that the more branched structure, the lower equilibrium melting point of B-PET which is originated from the reduced energy barrier of crystallization induced by less undercooling and therefore increasing the stacking thickness of lamellae crystal. Furthermore, it was also found that introducing the branched monomer indeed declined the orientation of PET crystalline which came from that the branched structure would impede the motion of polymer chain, decrease the regularity of polymer chain arrangement along the stretching direction and reduces the crystallinity. The hydrolysis resistance and dimension stability could be also improved through introducing more branched monomer.
In the third part of this study, a novel linear LCP polymer having better thermal resistance property was synthesized through condensation reaction and the effect of different heat setting process on the microstructure and thermal resistance of LCP thin film with various different viscosities (IV) was investigated by utilizing wide angle X-ray diffraction (WAXD). According to our observation, it is proved that the phase transition of microstructure in LCP thin film could be induced through heat setting process. This phase transition from a rather irregular hexagonal phase to a more orient orthorhombic phase elevated the thermal resistance of LCP thin film with ca. 40 ℃. Moreover, the fact that increasing the viscosity would elevate the thermal resistance rapidly was also observed; however, there is no obvious effect of tuning heat setting process when IV is very small (~ 4.18). This observation may because of that a certain length of polymer chain is required to form a stable crystalline structure arrangement with orthorhombic phase.
Aiming at overcoming the conventional rheological weakness of LCP polymer material on thin film engineering, a novel branched LCP polymer material is synthesized through unique design of molecular structure and introducing TMA monomer in condensation reaction. In this comprehensive study, this novel material was found having outstanding thermal resistance, high dimension stability, excellent mechanical properties and peerless color performance. With further investigation of the rheological behavior of this material, it was found that through introducing the branch monomer, the properties of melting strength, ductility and rheology with entanglement would be demonstrably elevated to meet the requirements of thin film processing. In the end, the resultant LCP thin film exhibiting extraordinary properties of low dielectric constant (Dk), low dielectric loss (Df), low thermal expansion coefficient and low hygroscopicity could satisfy the demand of FCCL for the next generation (e.g. 5G) high frequency/transmission speed application.

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