Physico-Chemical nanomaterials science

Influence of substituents on photo-physical properties of methacrylic polymers containing quinoline azo-dyes in side chain

D. Chomicki1, O Kharchenko2, L. Skowronski3, J. Kowalonek4, V. Smokal2, O. Krupka2,
B. Derkowska-Zielinska1

1 Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziadzka 5, 87-100 Torun, Poland
E-mail: chomicki@doktorant.umk.pl
2 Faculty of Chemistry, Taras Shevchenko National University of Kyiv, Volodymyrska 60, 01033 Kyiv, Ukraine
3 Institute of Mathematics and Physics, UTP University of Science and Technology, S. Kaliskiego 7, 85-796 Bydgoszcz, Poland
4 Faculty of Chemistry, Nicolas Copernicus University in Torun, Gagarina 7, 87-100 Torun, Poland

	Azobenzenes are an important class of organic dyes, which have found many optical applications such as optical switching, optical data storage and surface relief holography. One of their important features is the reversible trans-cis photoisomerisation. It should be mentioned that these two isomeric forms of azobenzenes have different spectroscopic properties [1, 2].
	The goal of our study was to study the influence of various substituents in the chromophores on the spectroscopic properties of methacrylic polymers containing quinoline azo-dyes in side chain (Fig. 1). The thin films of studied polymers were prepared by spin-coating technique. The extinction coefficient and refractive index were determined based on spectroscopic ellipsometry measurements (V-VASE ellipsometer, J.A. Woollam Co., Inc.) for three angles of incidence (65º, 70º and 75º). The transmittance measurements were carried out by Cary 5000 spectrometer in the UV-VIS spectral range (275-2000 nm). To characterize the topology of the layers atomic force microscopy (AFM) measurements were done using MultiMode NanoScope IIIa (Veeco Metrology Inc., USA) in air and at room temperature [3]. Photoisomerisation rates were investigated by measuring changes of absorbance during sample irradiation with UV light (365 nm) using Varian Cary 50 Scan UV-Visible Spectrometer (Agilent). 
	We found that the photo-physical properties of methacrylic polymers containing quinoline azo-dyes strongly depend on the type of substituent. The absorption spectra of studied compounds are shifted to the longest wavelengths compared to a neutral azo dye. The process of photoisomerisation is also observed.

Figure 1. Chemical structure of methacrylic polymers with quinoline azo-dyes in side chain.

1.	B. Derkowska-Zielinska, K. Fedus, H. Wang, C. Cassagne, G. Boudebs, Optical Materials 72 (2017) 545-548.
2.	B. Derkowska-Zielinska, O. Krupka, V. Smokal, A. Grabowski, M. Naparty, L. Skowronski, Molecular Crystals and Liquid Crystals 639 (2016) 87-93. 
3.	B. Derkowska-Zielinska, L. Skowronski, M. Sypniewska, D. Chomicki, V. Smokal, O. Kharchenko, M. Naparty, O. Krupka, Optical Materials 85 (2018) 391-398.