Self-assembly behaviour of telechelic polyethylene glycol with triptycene termini capable of two-dimensional ordering

Abstract

The self-assembly of polymers into well-defined structures is of great interest in the design of functional materials. We have previously shown that telechelic polydimethylsiloxanes bearing 1,8,(13)-substituted triptycene termini form highly ordered “2D + 1D” structures, which significantly improve their rheological and thermal properties. In this study, to gain insight into the scope and limitations of this terminal-triptycene-driven polymer ordering, we investigated a new system based on crystalline polyethylene glycol (PEG). We synthesised telechelic PEGs with 1,4-, 1,8- and 1,8,13-substituted triptycenes (i.e., 1,4-, 1,8- and 1,8,13-Trip-PEGs) to examine how the substitution pattern of the triptycene termini influences polymer self-assembly. In water, 1,4- and 1,8-Trip-PEGs form hydrogels without long-range ordering, while 1,8,13-Trip-PEG forms a hydrogel with a well-defined “2D + 1D” structure. The critical gelation concentration decreases as the self-assembly ability of the terminal groups increases. In the solid state, the structures of 1,4- and 1,8-Trip-PEGs are dominated by PEG crystallisation. In contrast, 1,8,13-Trip-PEG forms a distinct ordered structure regardless of whether the PEG chains are melted or crystallised. These results demonstrate the strong ability of 1,8,13-substituted triptycene termini to induce structural ordering, even in crystalline polymers.