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Comparative study of PEG and PEGylated dendrimers in their eutectic mixtures with water analyzed using X-ray diffraction and infrared spectroscopy


It has been reported that the hydration state of biocompatible polymers, such as poly(ethylene glycol) (PEG), affects their bioinertness. PEGylated dendrimers have been studied for use as drug carriers. In our previous study, the hydration behaviors of PEG and PEGylated dendrimers were analyzed using differential scanning calorimetry (DSC) to investigate the relationship between hydration and in vivo behaviors. In this study, the hydration behaviors of PEG and PEGylated dendrimer were analyzed using X-ray diffraction (XRD) and infrared (IR) spectroscopy. According to the XRD analysis, ice was formed and melted in the PEG/water mixture with a 20% water content below 0 °C during the heating process; however, PEG crystals were formed in the PEG/water mixture containing 70% water. The XRD and IR results of the PEGylated dendrimer/water mixture were similar to those of the PEG/water system containing 70% water. Our IR spectral studies indicated that the hydration state of the PEGylated dendrimer was different from that of PEG containing 20% water. These results suggested that a comprehensive study is important for the analysis of such eutectic mixtures of PEG compounds and water.

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We would like to thank Ms. Maya Okada and Mr. Junjie Yao (Osaka Prefecture University) for their help with figure and sample preparation, respectively. This work was supported by JSPS KAKENHI Grant Numbers JP19H05720, JP19H05717, and JP20H05232 (Grant-in-Aid for Scientific Research on Innovative Area: Aquatic Functional Materials). The XRD and FT-IR experiments were performed at BL40B2 and BL43IR of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (JASRI) (Proposal Nos. 2021A1069, 2021B1366, and 2022A1202), respectively. YS acknowledges experimental support from Dr. Noboru Ohta and Dr. Hiroshi Sekiguchi at SPring-8. We would like to thank Editage ( for English language editing.

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Kojima, C., Suzuki, Y., Ikemoto, Y. et al. Comparative study of PEG and PEGylated dendrimers in their eutectic mixtures with water analyzed using X-ray diffraction and infrared spectroscopy. Polym J 55, 63–73 (2023).

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