Abstract
Much attention has been devoted to precise control of the size and morphology in nanosized molecular assemblies for a wide range of materials applications. Recently, we reported observing submicron/nanosized polyion complex vesicles (Nano-PICsomes) with a narrow size distribution, synthesized using specific types of homocatiomers and polyethylene glycol (PEG)-based block aniomers. However, only one example of Nano-PICsomes has been reported to date. Here, the role of the chemical composition of PEG-based block aniomers and the chemical structures of the side chains of homocatiomers were carefully examined to better understand the formation of Nano-PICsomes. Transmission electron microscopy and dynamic light scattering analyses of Nano-PICsomes revealed that a longer length of ionic segments in the block aniomers or a PEG weight fraction (fPEG) <10%, is required for the selective formation of Nano-PICsomes, whereas polymer combinations with fPEG >10% produced spherical micelles. In addition, the homocatiomers containing longer aliphatic side chains (e.g., five or six carbon atoms) favored the formation of Nano-PICsomes, whereas those containing shorter aliphatic side chains produced irregularly shaped PIC micelles. Accordingly, fPEG and the length of the side chain were found to be the key factors that control the morphologies of Nano-PICsomes. Insights gained from this study can broaden the spectrum of the design of Nano-PICsomes for use in a diverse range of material applications.
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Acknowledgements
This research was supported in part by a Grant-in-Aid for Scientific Research (no. 23685037 and 23106705 to A. K.) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT) of Japan and by the Japan Society for the Promotion of Science (JSPS) through the ‘Funding Program for World-Leading Innovative R&D on Science and Technology (FIRST Program),’ initiated by the Council for Science and Technology Policy (CSTP). A part of this work was conducted in the Research Hub for Advanced Nano Characterization, University of Tokyo, supported by MEXT of Japan. We are grateful to Dr S. Fukuda, University of Tokyo Hospital and Mr. H. Hoshi, Research Hub for Advanced Nano Characterization at the University of Tokyo, for their valuable support in performing the TEM measurements.
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Chuanoi, S., Kishimura, A., Dong, WF. et al. Structural factors directing nanosized polyion complex vesicles (Nano-PICsomes) to form a pair of block aniomer/homo catiomers: studies on the aniomer segment length and the catiomer side-chain structure. Polym J 46, 130–135 (2014). https://doi.org/10.1038/pj.2013.82
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DOI: https://doi.org/10.1038/pj.2013.82
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