Thermoresponsive reversible host-guest supramolecular nanotubular self-assembly of octyl-2-acetoxybenzoate@β-CD

Abstract

The present work deals with supramolecular host–guest complexation of octyl-2-acetoxybenzoate (OCASP) into β-cyclodextrin (β-CD) which spontaneously self-assembled into a thermoresponsive nanotubular architecture at a molar ratio of 1:1. OCASP was synthesized as a prodrug of aspirin (ASP) in an aim to reduce its inherent toxicity. The OCASP@β-CD inclusion complex (IC) was characterized by UV–Vis, FT-IR, WAXRD, 13C CP/MAS NMR spectroscopy and SEM. TEM and AFM revealed the formation of nanotube with a diameter of ∼50 nm. Reversible switching of assembly and disassembly is triggered by decreasing and increasing of temperature, as is evidenced by the turbidity measurement of a 5% solution of OCASP@β-CD system. Hydrophobic interactions among the successive OCASP@β-CDs are the chief driving force behind the formation of hierarchy as is evidenced by the control experiment with urea during its preparation. The stepwise formation of such a hierarchy was further characterised by molecular dynamics (MD) studies in 15 ns time scale using 2 fs time step. The developed stimuli responsive system would permit tailoring of its physical properties and it is anticipated that it will bring light on the fabrication of novel smart materials.