Abstract: Several polycations, poly[trialkyl-(4-vinylbenzyl)ammonium] chlorides have been synthesised. When salts are introduced into solution of the water-soluble polymers, thermo-responsive behavior is observed. The type of transition is dependent on the length of the alkyl chain: the polymer with an ethyl chain has an upper critical solution temperature (UCST) whereas the polymers with butyl or pentyl chains have a lower critical solution temperature (LCST). The magnitude of the effect of a given salt on the solution behavior is dependent on the type of the used electrolyte.[1]

 

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A series of diblock copolymers consisting of poly(vinylbenzyl trimethylammonium triflate) and PEG blocks have been studied in detail, with a purpose to find out whether the collapsed polymer particles may be stabilized with the PEG blocks.[2,3] The length of the PEG block was kept constant and the DP of the polycation was varied. The figure shows the transmittance of solutions of four polymers upon cooling. Polymers with a short cationic block turn cloudy and partially clear again during a temperature decrease, whereas those with a long cationic block phase separate and slowly precipitate and remix only when heated. Phase separation takes place via particle formation, and we suggest different mechanisms for colloidal stabilization of particles composed of short or long chains.

References

[1] E. Karjalainen, N. Survali, H.Tenhu; Polymer Chemistry (ahead of print) DOI: 10.1039/d0py00917b

[2] V. Baddam, V. Aseyev, S. Hietala, E. Karjalainen, H. Tenhu; Macromolecules 51 (2018), 9681-9691

[3] V. Baddam, R. Miissonen, S. Hietala, H. Tenhu; Macromolecules 52 (2019), 6514-6522

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