Synthesis and Physical Properties of UV Curable Liquid-Crystalline Acrylate Nanocomposites

本研究合成並使用一種液晶壓克力4,4''-bis(3-hydroxyalkyloxy) biphenyl diacrylates (B3A)，使其在具有液晶形態及完全熔融的狀態下照光聚合並比較其性質的差異。液晶型態下照光聚合的壓克力相對於非液晶型態下聚合的壓克力的機械性質有顯著的提升，硬度提高20%。因此我們可將液晶結構的形成視為一種自增強(self-reinforced)效應，此效應帶來的好處就是不需額外添加無機填料就可達到相當高的機械強度。 接著我們探討混摻無機奈米粒子後性質的改變。第一部分混入不同比例以矽烷偶合劑3-(Trimethoxysilyl) propylmethacrylate (MPS)改質的二氧化矽奈米粒子，可有效提升材料的硬度且提高其熱裂解溫度(Td)、儲存模數及玻璃轉化溫度(Tg)。但隨著二氧化矽的固含量增加，液晶形態在機械強度提升上有平緩的趨勢。利用XRD研究後發現液晶特徵峰有越來越寬的趨勢，顯示液晶形成範圍受到奈米粒子多寡的影響而越來越小。第二部分我們使用不同長寬比的二氧化鈦粒子，觀察混摻後對液晶排列的自增強現象的影響。混摻二氧化鈦奈米桿(長寬比約為4)的複材，在添加量超過2%之後複合材料的液晶行為就無法使用偏光顯微鏡做簡易的觀察，因為添加了更多量的奈米桿，將使得液晶形成範圍受到限制而變小，影響到可見光的觀察範圍。而混摻二氧化鈦奈米粒子的複材，在偏光顯微鏡下不會觀察到和二氧化鈦奈米桿相同的情況。 因此複合材料的性質除了取決於填入高分子基材中的無機奈米顆粒本身的性質、形狀及表面改質的不同有所差異外，也會受到高分子基材的排列而有所不同。In this research, we have synthesized and utilized a liquid crystalline(LC) acrylate, 4,4''-bis(3-Hydroxy- alkyloxy) biphenyl diacrylates(B3A). We have photo cured the B3A either at LC state or at isotropic state and compared the difference of cured properties between two state. Hardness of the sample with LC structure after photocure exhibits 20% higher than the amorphous one. The result is due to the self reinforcing effect from the LC structure remained in the sample after cured. We further improved the physical properties of the B3A by incorporating nanofiller to from nanocomposite. We studied the effect of nanofiller on the formation of LC state in the cured sample. In the first part of this work, we added SiO2 particle which modified with 3-(Trimethoxysilyl) propylmethacrylate (MPS) in acrylate resin. SiO2 enhances its decomposition temperature (Td), storage modulus and glass transition temperature (Tg) effectively. But when the content of SiO2 is further increased, the increase in mechanical property is less significant. In the XRD study, the peak of LC structure is broader as increasing the content of SiO2. It shows that the increased amount of SiO2 decrease the domain size of LC structure. In the second part, nanofillers with different aspect ratios, TiO2 nanorod(TNR) and TiO2 nanoparticle(TNP) are added to acrylate resin to investigate their effect on the LC structure formation and self-reinforcing effect. In TNR nanocomposite series, when we increase TNR contain to 2wt%, that is difficult to find large domain LC structure under POM analysis. Due to the increased amount of TNR limit the formation of LC structure. The trend in TNP nanocomposite series matched up with the trend in SiO2 composite series, but the effect on the physical properties by TNP is less obvious. In conclusion, we observe that the nanocomposites are dependent on the inorganic nanofiller’s shape and the interface interaction of polymer-inorganic. Additionally, the properties of nanocomposites are also affected by the presence of LC structure