Abstract
The aim of this work is to demonstrate that the alkylation and dealkylation of selenium atoms is an effective tool in controlling polymer amphiphilicity and, hence, its assembly and disassembly process in water. To establish this concept, poly(ethylene glycol)-block-poly(glycidyl methacrylate) was prepared. A post-synthesis modification with phenyl selenolate through a base-catalyzed selenium-epoxy ‘click’ reaction then gave rise to the side-chain selenium-containing block copolymer with an amphiphilic character. This polymer assembled into micellar structures in water. However, silver tetrafluoroborate-promoted alkylation of the selenium atoms resulted in the formation of hydrophilic selenonium tetrafluoroborate salts. This enhancement in the chemical polarity of the second polymer block removed the amphiphilic character from the polymer chain and led to the disassembly of the micellar structures. This process could be reversed by restoring the original amphiphilic polymer character through the dealkylation of the cations.
Highlights
In nature, reversible methylation and demethylation processes play a critical role in determining protein structure and function [1]. In synthetic polymers such reversible alkylation/dealkylation-based strategies are not employed in controlling polymer properties
We envisaged that the methylation of selenium (Se) atoms to selenonium (Se+) cations would result in a large change in the chemical polarity of the system
If a copolymer chain contains a hydrophilic block and an organoselenium-based [2,3,4,5,6,7,8,9,10,11,12,13] hydrophobic block, it would assemble in water due to an amphiphilic nature of the polymer (Figure 1)
Summary
Reversible methylation and demethylation processes play a critical role in determining protein structure and function [1]. In synthetic polymers such reversible alkylation/dealkylation-based strategies are not employed in controlling polymer properties. Towards this end, we envisaged that the methylation of selenium (Se) atoms to selenonium (Se+) cations would result in a large change in the chemical polarity of the system. If a copolymer chain contains a hydrophilic block and an organoselenium-based [2,3,4,5,6,7,8,9,10,11,12,13] hydrophobic block, it would assemble in water due to an amphiphilic nature of the polymer (Figure 1). If the selenium-containing polymer block is methylated, its chemical nature would change to reflect a hydrophilic character. If the alkylation and dealkylation can be carried out in a reversible fashion, the polymer micelles could be formed and broken through the methylation/demethylation of selenium atoms
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