A study on the phase evolution of calcium phosphates (CaPs) in the presence of an ionomer is of great significance for understanding their intriguing behavior and applications. Nafion, as an ion exchange ionomer of perfluorosulfonic acid, could tune the formation of CaP and phase evolution due to its inherent acidity, ion exchange feature and specific morphology in solution. When the initial pH of the incubating dispersion was adjusted to 5, monetite (CaHPO₄, DCPA) was obtained in the presence of Nafion; the product differs from the DCPD formed from the solution in the absence of the ionomer. Under an alkaline condition (initial pH 9), the formation of hydroxyapatite (Ca₁₀(PO₄)₆·(OH)₂, HAP) could be effectively tuned by Nafion; octacalcium phosphate (Ca₈H₂(PO₄)₆·5H₂O, OCP) preliminarily formed in the presence of a high number of calcium ions (Ca/P = 0.2 M/0.1 M). In contrast, brushite (CaHPO₄·2H₂O, DCPD) was the main product with a low concentration calcium ion source (Ca/P = 0.1 M/0.2 M). Nafion plays an essential role to facilitate the deprotonation process to extend the transition for HAP formation via the DCPD dissolution–reprecipitation process. The rod-like HAP was formed by the induction of the elongated pattern Nafion with the ion exchange behavior of its side chain. The results acquired in this work not only provide a new route for the controlled preparation of CaP precursors but also help us to better understand the electrochemical behavior of CaPs assisted by Nafion.

中文翻译：

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离子交换离聚物Nafion调节磷酸钙的形成和相演化

在离聚物的存在下对磷酸钙（CaPs）的相演化进行研究对于理解其有趣的行为和应用具有重要意义。Nafion作为全氟磺酸的离子交换离聚物，由于其固有的酸度，离子交换特性和溶液中的特定形态，可以调节CaP的形成和相的演变。当将孵育分散液的初始pH调节至5时，在Nafion的存在下获得了透钙沸石（CaHPO ₄，DCPA）。该产物不同于在没有离聚物的情况下由溶液形成的DCPD。在碱性条件下（初始pH 9），形成羟基磷灰石（Ca ₁₀（PO ₄）₆ ·（OH）_2），HAP）可以由Nafion有效地进行调整；在大量钙离子（Ca / P = 0.2 M / 0.1 M）存在下初步形成磷酸八钙（Ca ₈ H ₂（PO ₄）₆ ·5H ₂ O，OCP）。相反，透钙磷石（CaHPO ₄ ·2H ₂ O，DCPD）是具有低浓度钙离子源（Ca / P = 0.1 M / 0.2 M）的主要产品。的Nafion起着至关重要的作用，以促进脱质子化处理，以延长HAP形成的过渡经由DCPD溶解-再沉淀过程。棒状HAP是通过诱导长形的Nafion及其侧链的离子交换行为而形成的。这项工作获得的结果不仅为控制CaP前体的制备提供了一条新途径，而且还有助于我们更好地了解由Nafion辅助的CaP的电化学行为。