Think Positive: Phase Separation Enables a Positively Charged Additive to Induce Dramatic Changes in Calcium Carbonate Morphology
Think Positive: Phase Separation Enables a Positively Charged Additive to Induce Dramatic Changes in Calcium Carbonate Morphology
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DOI：
10.1002/adfm.201102385
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发表时间：
2012-03-07
影响因子：
19
通讯作者：
Meldrum, Fiona C.
中科院分区：
文献类型：
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作者：
Cantaert, Bram;Kim, Yi-Yeoun;Meldrum, Fiona C.
可溶性大分子对自然界控制生物矿物质的形成至关重要。在早期从珍珠质中提取富含天冬氨酸和谷氨酸的大分子后，研究重点是使用带负电荷的添加剂来控制碳酸钙的沉淀。结果表明，带正电荷的添加剂聚丙烯胺盐酸盐（PAH）也可以引起方解石形态的剧烈变化，产生类似于聚天冬氨酸通过所谓的PILP（聚合物诱导液体前驱体）相产生的CaCO3薄膜和纤维。通过低温透射电子显微镜（TEM）、拉曼显微镜和热重分析等一系列技术，研究了多环芳烃诱导这些效应的机制。数据显示，水合Ca2+/多环芳烃/CO32-液滴最初在溶液中形成，然后聚结并最终结晶形成方解石，以及少量的水合水晶石。研究表明，这一过程的关键是水合Ca2+/PAH/CO32-液滴的初始形成，而不是特定的聚合物/矿物相互作用。这些结果与生物矿化过程的相关性进行了讨论，并强调了利用反离子诱导的聚电解质相分离作为产生非晶体形态矿物的方法的机会。
Soluble macromolecules are essential to Nature's control over biomineral formation. Following early studies where macromolecules rich in aspartic and glutamic acid were extracted from nacre, research has focused on the use of negatively charged additives to control calcium carbonate precipitation. It is demonstrated that the positively charged additive poly(allylamine hydrochloride) (PAH) can also cause dramatic changes in calcite morphologies, yielding thin films and fibers of CaCO3 analogous to those produced with poly(aspartic acid) via a so-called PILP (polymer-induced liquid precursor) phase. The mechanism by which PAH induces these effects is investigated using a range of techniques including cryo transmission electron microscopy (TEM), Raman microscopy, and thermogravimetric analysis, and the data show that hydrated Ca2+/PAH/CO32- droplets initially form in solution, before coalescing and ultimately crystallizing to give calcite, together with small quantities of vaterite. It is suggested that it is the initial formation of hydrated Ca2+/PAH/CO32- droplets that is key to this process, rather than a specific polymer/mineral interaction. These results are discussed in terms of their relevance to biomineralization processes and highlight the opportunity for using counter-ion-induced phase separation of polyelectrolytes as a method for generating minerals with non-crystallographic morphologies.