17.09.2020
12:00-12:40 EET
11:00-11:40 CET
10:00-10:40 BST
Francoise M. Winnik
University of Helsinki,
Finland
Azobenzene- triggered photoresponsive polymers and beyond: Toward soft robots.
Abstract: Among the various stimuli for responsive polymer-based materials, light possesses several advantages: it is directional, tunable in terms of energy, and it can be turned on and off rapidly. Azobenzene, which undergoes reversible trans to cis photoisomerization, is commonly used for applications. in view of its stability, tuneability, and reliability. Current trends towards miniaturization, which often require faster and more versatile photoswitches, has led to the development of heteroaryl azo dyes, such as azopyridine AzPy (Figure 1) AzPy possesses all the chemical features associated with the pyridine nitrogen atom and offers chemical opportunities unattainable with azobenzene.
Figure 1.
Unlike azobenzene, AzPy can affect the thermoresponsive behavior of polymers in response to three orthogonal triggers: pH, through changes in ionization; light, via trans-cis photoisomerization; and time, from hours to a few ms, via the kinetics of the dark the cis-trans relaxation. The key features of azopyridines will be illustrated based on recent studies of AzPy-modified poly(N-isopropylacrylamide) (PNIPAM-AzPy) in aqueous solution.(1,2) Applications of AzPy as sensors and actuators in the form of hydrogels and films will be described.
References:
1) H. Ren, X. Qiu, Y. Shi, P. Yang and F. M. Winnik, Macromolecules, 2019, 52, 2939-2948. 2) H. Ren, X. Qiu, Y. Shi, P. Yang and F. M. Winnik, Polym. Chem.-Uk, 2019, 10, 5080-5086