Khalid Naim

Project title: Conformational switches as mechanophores for tuning optical properties, mechanical properties and photosensitization

Host Institution: Eindhoven University of Technology (TU/e)

Host Supervisor: Prof. Rint Sijbesma

Co-host Institution: Technion Israel Institute of Technology

Co-host Supervisor: Dr. Charles E. Diesendruck

Summary project: The term “mechanophores” refers to molecules that change their chemical and physical properties under mechanical stress.

In this project, I will create a new type of highly sensitive mechanophores based on cyclohexane conformational switches that adjust their optical, mechanical or photosensitization properties when conformations are manipulated by mechanical force as a stimulus. The cyclohexane based conformational switches will be incorporated in linear polymers and in polymer networks to transfer macroscopic stress to the mechanophores. The ground-state conformation of the switches will be tuned by the rational incorporation of appropriate substituents. Donor/acceptor, host/guest, and photosensitizer/heavy atom pairs will be used to modulate the mechanical, physical/optical and/or photosensitization properties of conformational switching mechanophores.

The new mechanophores will be useful in three different areas: i) to create sensitive molecular strain sensors. ii) to tune the photosensitization properties of photosensitizers attached to the conformational switching mechanophores as a novel method to control their activity in photodynamic therapy of cancer, and iii) to improve mechanical properties of polymers by energy dissipation through the reversible disruption of intramolecular interactions. To reach these goals, a systematic investigation of the effect of mechanical stress on the mechanical and photophysical properties of these materials will be undertaken.