操作變數對CaCO3/有機複合薄膜之影響

Effects of Operating Variables on the morphology of CaCO3/Organic Hybrid Thin-Film

周哲宇(Che-Yu Chou)

指導教授 ： 王勝仕

共同指導教授 ： 戴怡德(Yi-Der Tai)

國立臺灣大學/工學院/化學工程學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.01242

摘要

生物礦物為具有高度定序和複雜的無機/有機混合物，如貝殼珍珠層、海膽的針狀外殼、牙齒和骨骼。這些結構可形成於溫和的條件，但形成的過程受到巨分子模板控制，如蛋白質、肽和聚醣類。材料科學家可從這些生物礦物的結構、性能和形成機制得到靈感，進而合成仿生材料。Kato等人進行一連串生物體外實驗，以CO2通氣法(Kitano法)配製碳酸鈣過飽和溶液且加入可溶性高分子，此可溶性高分子於水溶液中形成帶負電的離子而與鈣離子結合以防成核，而使碳酸鈣薄膜在固體模板上成長。利用CO2通氣法雖然操作流程簡易，可用於討論可溶高分子/固體模板的效應，但是無法控制過飽和溶液組成與pH值，且配製時間過長(大約5小時)，同時成長時間亦太長(大約4天)，若希望進一步討論過飽和溶液各項變數對碳酸鈣薄膜之影響，則實驗方法必須設法改進。
本研究第一步為重現Kato等人(1998)與(2000)實驗，其實驗目的為找出合適的可溶性高分子與固體模板。Kato等人(1998)選用聚丙烯酸(PAA)與甲殼素(chitosan)，而Kato等人(2000)選用聚天冬胺酸(PAsp)與甲殼素(chitosan)。從重現實驗結果皆可得到碳酸鈣薄膜，但與Kato等人之結果比較發現薄膜表面結構有明顯不同。
本實驗室技術可配製且控制過飽和溶液組成於介穩區，其方法為將所需的條件輸入電腦程式，並且計算出所需加入碳酸鈉與氯化鈣的量，再緩慢依序將兩者混和，此方法之溶液變數控制較易且配製時間短(大約1小時)，因此運用此技術改良過飽和溶液配製方法。在模板方面，可溶性高分子為聚丙烯酸(成本低)，而固體模板為甲殼素，因其製備容易。本研究第二步為運用本實驗室技術於液相批次系統中進行過飽和度效應和離子活性比效應之探討，其目的為得到形成碳酸鈣薄膜之條件。在過飽和度效應中，發現形成碳酸鈣薄膜之過飽和度必須高於6以上，而離子活性比效應中，發現當離子活性比提高使碳酸鈣薄膜直徑變小且表面具有紋路。
從液相批次系統中得知本實驗室技術可成功製備出碳酸鈣薄膜，因此將系統發展至液相流動系統，進而深入討論pH值與PAA濃度對碳酸鈣薄膜晶相的影響，發現pH值與PAA濃度對碳酸鈣晶相皆有極大的影響，其中在pH=10.0時，可得到最多的霰石薄膜；另外，PAA濃度與霰石比例呈現反比關係，但是當PAA濃度低至無法抑制成核時，溶液則開始成核而微粒落於薄膜表面上。
本實驗室已發表許多關於磁場作用於碳酸鈣過飽和溶液的實驗，從中得知磁場作用下可利於形成和成長霰石。因此最後本研究將磁場引進液相流動系統中，當系統加入磁場後，發現碳酸鈣薄膜晶相確實傾向於形成霰石，而有助於合成純度更高的霰石薄膜。

關鍵字

仿生材料 ； CaCO3/有機複合薄膜 ； 操作變數效應 ； 磁場效應

並列摘要

Biominerals, such as the nacre of shells, spicules of sea urchins, teeth, and bones are inorganic-organic hybrids that have highly controlled hierarchical and complex structures. These structures are formed in mild conditions, and the processes are controlled by macromolecular templates of proteins, peptides, and polysaccharides. Materials scientists can obtain ideas from the structures, properties, and formation processes of biominerals for use in creating synthetic, biomimetic materials. Kato et al. conducted a series of experiment in vitro. Thin-film crystals of CaCO3 had been developed on the surface of solid matrices from supersaturated calcium bicarbonate solution using Kitano’s method in the presence of the soluble polymer. Although the Kitano’s method, i.e. by bubbling CO2 gas, was simple to operate and able to discuss the effect of the soluble polymer/solid matrices, the composition of supersaturated solution can’t be controlled; moreover, it took too long to finish an experiment, about 5 hours spent on solution preparation and five days on crystal growth. If we intend to study the operating variables on the growth behavior of CaCO3 film, the experimental method should be improved.
Beginning of our research, the suitable soluble polymer and the insoluble matrix were found by repeating the Kato’s experiments. Kato et al. (1998; 2000) selected poly(acrylic acid)/chitosan and poly(aspartic acid)/chitosan as the soluble polymer/the solid matrix respectively. Nevertheless, the surface structure of the CaCO3 thin-film is different from that reported by Kato et al. (1998; 2000).
The technique developed in our laboratory can be used to prepare and control supersaturated solution falling on the metastable region. Through the computer programs the required amount of NaCO3 and CaCl2 were calculated and then they were slowly mixed to form the supersaturated solution. It took about 1 hour for the solution preparation. As far as the matrix is concerned, poly(acrylic acid), which is cheap, and chitosan, which is easy to prepare, were used as the soluble polymer and solid matrix. In the second stage of our research the liquid-phase batch system was adopted to search for the operating conditions suitable for film growth, with emphasis on supersaturation and activity ratio. Thin-film of CaCO3 formed on the chitosan matrix, when the supersaturation was higher than 6. The surface of thin-film of CaCO3 were more rough, when the activity ratio was higher.
The experiment was further carried on using the liquid-phase circulating system. We discussed that effect of the solution of pH and the concentration of PAA on the morphology of the CaCO3 thin-films. The results indicated the solution of pH and the concentration of PAA both had a great effect on the morphology of the CaCO3 film. When the solution pH was 10.0, the mole fraction of aragonite reached a maximum value. On the other hand, the mole fraction of aragonite decreased with an increase in the PAA concentration. When the concentration of PAA was too low to inhibit nucleation, the particles fell on the film from the bulk solution.
Finally, a magnetic field was incorporated into the liquid-phase circulating system, because the magnetic effect was in favor of aragonite formation and growth formed in our laboratory. Thin-films of CaCO3 had a tendency to form aragonite film, when the system was in the presence of a magnetic field.

並列關鍵字

biomimetic material ； CaCO3/organic hybrid thin-film ； effect of operation variables ； effect of magnetic field

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