As for NMR results (Fig. )), all peaks in ZrHEDP samples are broad compared to those in HEDP. The broadness indicated that all phosphonic acid groups are immobile and fixed to Zr layers, and thus no free HEDP remained in ZrHEDP samples. The specific assignment for P peaks in ZrHEDP is more complex than the corresponding bands for other zirconium such as biphenylene-bisphosphonates, likely due to the angular nature of the ether-bisphosphonate unit, which imposes two different orientations with the inorganic layer. Nevertheless, the peak of the more freely movable 31 P atom was expected to shift to a lower field. Therefore, the peaks at 3 and 13 ppm can be attributed to the movable -PO3H2 and the immobilized -PO3-in the Zr-O-network layer, respectively. Furthermore, the intensity of peaks at 3 ppm became stronger as the value of the P/Zr ratio increased. Therefore, these results suggested that ZrHEDP with a higher P/Zr value contains a lot of -PO3H2 moieties, which matches the above indications from the ICP-AES results. These two results mean that ZrHEDP samples have the mixture of structures illustrated in Fig. )-(e), and the large amount of -PO3H2 moieties existed in the ZrHEDP with high P/Zr.