Abstract
The synthesized linear poly(N-methylethylene imine) (PMEI; weight-average molecular weight, 26 kDa) has been characterized in terms of its solubility, titration behavior, lower critical solution temperature (LCST)- and upper critical solution temperature (UCST)-type phase separations, self-aggregation and aggregation behaviors with polystyrene (PS) latex particles. PMEI is soluble in several solvents (that is, from nonpolar n-hexane above 45 °C to polar water at room temperature) and exhibits a UCST-type phase separation in toluene at 36 °C. The pKa value of PMEI is 7.28. An aqueous PMEI solution exhibited LCST-type phase behavior, and the LCST was determined to be 116 °C with the aid of the salting out effect. PMEI chains formed aggregates with negatively charged PS latex particles, and the aggregate structure was dependent on the PMEI concentration. In the vicinity of the isoelectric point, the PMEI-PS aggregates grew larger and precipitated, and at higher PMEI concentrations, the aggregates were positively charged and uniformly dispersed. In conclusion, PMEI is expected to be used as a highly hydrophilic and versatile polycation.
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Acknowledgements
We thank Mr Kenta Kato (DJK Corporation) for performing the SEC measurement; the late Dr Joachim H. G. Steinke (Imperial College, UK) for visiting us to give valuable advice on the polymer synthesis; and Dr Kayori Takahashi, Dr Haruhisa Kato and Dr Shinichi Kinugasa (National Institute of Advanced Industrial Science and Technology) for helpful advice on the SLS experiment. This study was partially supported by the Grants-in-Aid for Scientific Research (B) (18350112) and (C) (22550190 and 16K05906) from the Japan Society for the Promotion of Science.
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Fukuda, Y., Abe, D., Tanaka, Y. et al. Solution properties of poly(N-methylethylene imine), a highly hydrophilic polycation. Polym J 48, 1065–1072 (2016). https://doi.org/10.1038/pj.2016.71
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DOI: https://doi.org/10.1038/pj.2016.71
