Light‐Induced Transformation of a Supramolecular Gel to a Stronger Covalent Polymeric Gel

Abstract

A polymerizable diacetylene gelator, containing urea and urethane groups, that congeals various non‐polar solvents was synthesized. The gelator molecules self‐assemble forming non‐covalent polymers through intermolecular hydrogen bonding, as evidenced from FT‐IR and concentration‐dependent 1H NMR spectroscopy. The self‐assembly positions the diyne units of adjacent molecules at proximity and in a geometry suitable for their topochemical polymerization. UV irradiation of the gel resulted in topochemical polymerization, transforming the non‐covalent polymer to a covalent polymer, in situ, in the gel state. The polymerization was confirmed by characterizing the polydiacetylene (PDA) using UV‐Vis and Raman spectroscopy. Time‐dependent rheological studies revealed gradual strengthening of the gel with the duration of irradiation, suggesting that the degree of polymerization increases with the duration of irradiation. The PDA formed is a semiconductor, which might be useful for various applications.