Supramolecular blends of C-alkylpyrogallol[4]arenes and polytetrahydrofurans

Abstract

A small series of the amphiphilic macrocycles – C-alkylpyrogallol[4]arenes has been synthesized and examined by single crystal X-ray analysis which showed the formation of two supramolecular arrangements depending on solvent used for crystallization, i.e., multilayered motif and hexameric capsule. Those structural findings provided an insight into blends prepared from aforementioned macrocycles and various polytetrahydrofurans (polyTHFs). Thus, 1:1 wt ratio mixtures were obtained and investigated by combination of Fourier-transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). As it turned out, the viscosity of these blends was increased compared to starting materials, which imply that pyrogallol[4]arenes can be successfully utilized as supramolecular cross-linkers enhancing H-bonding between adjacent macromolecular chains. As the major difference between compounds synthesized is the length and geometry of their respective alkyl side chains attached directly to macrocyclic core, i.e., n-propyl- and cyclohexyl- vs. n-dodecyl-, it seemed likely that even insignificant increase in their hydrophobicity can induce high order aggregation of nanoparticles in the slurries, thus affecting their viscosity. Overall, material viscoelastic properties are tunable at macroscopic level by choosing particular pyrogallol[4]arene/solvent combination and adjusting the temperature, which may be advantageous for the design of hybrid materials.