Topochemical polymerization in phenylalanine anchored chiral diacetylenes for chiroptical properties and tunable thermo-, halo-, solvatochromism

Abstract

Chiral polymers always have the edge over their achiral analogues owing to the effective utilization of asymmetry to mimic nature in multiple ways. Chirality in tandem with conjugation in polymers creates an excellent platform for optoelectronic properties, leading to futuristic applications based on chiral photonics. Herein, we design two symmetric bis-functionalised phenylalanine tethered chiral diacetylene (DA) monomers that exhibit efficient topochemical polymerization into conjugated ene–yne polydiacetylene (PDA) with an intense red colour. The efficacy of the photopolymerization can be modulated by altering the peripheral functional groups. Interestingly, the individual enantiomers and their mixture show comparable photopolymerization owing to co-assembly. However, the chiroptical properties of the mixtures can be tweaked by the enantiomeric excess complying with the majority rule principle. Finally, the individual chiral PDA exhibits visible changes in optoelectronic and chiroptical properties under external perturbation e.g. temperature, volatile organic solvent and pH, that are investigated using UV-visible and circular dichroism spectroscopy. Such topochemical polymerization assisted by ordered self-assembly in peptide-tethered diacetylene provides convenient access to smart, responsive, chiral optoelectronic materials.