Influence of methyl group in a quinoline moiety on optical and light-induced properties of side-chain azo-polymers

D Chomicki,V Smokal,B Derkowska-Zielinska,L Skowronski,O Krupka,J Kowalonek,O Kharchenko

doi:10.1007/s13204-021-01764-0

Abstract

We present the optical and photochromic properties as well as surface quality of thin films of the methacrylic copolymers containing 2-methylquinoline and quinoline azo-dyes in side chain. The extinction coefficient and refractive index were determined using spectroscopic ellipsometry combined with transmittance measurements. Photo-responsive behavior was investigated by determination of trans–cis photoisomerization rates under irradiation with unpolarized 365 nm light. We found that optical properties as well as photoisomerization rates of investigated polymers are dependent on the presence of a methyl substituent in the 2nd position of the quinoline moiety. The quality of the thin films was examined using Atomic Force Microscopy measurements.

Highlights

Azobenzene is a molecule consisting of two phenyl rings linked by an azo (-N=N-) bridge forming an extensive conjugated π-electron system (Sekkat and Knoll 2002; Bandara and Burdette 2012; Wang 2017)
We found that qA-H-CH3 and qA-OCH3CH3 samples have very smooth surfaces with roughness parameters values varying from 0.23 nm to 0.25 nm for Ra and from 0.31 to 0.41 nm for Rq before their irradiation
Replacing hydrogen atom with methyl group in R2 position and methoxy group in R1 position led to decrease in the surface roughness as these groups were bigger and they could rotate contributing to the occupation of energetically privileged

Summary

Introduction

Azobenzene is a molecule consisting of two phenyl rings linked by an azo (-N=N-) bridge forming an extensive conjugated π-electron system (Sekkat and Knoll 2002; Bandara and Burdette 2012; Wang 2017). Keywords Quinoline azo-dye polymers · Optical properties · Extinction coefficient · Refractive index · AFM · Photoisomerization Properties of azobenzene derivatives, such as absorption maximum position, refractive index, optical energy gap, isomerization rates, thermal stability, bond lengths, and dipole moment, can be tailored by introducing various substituents into the phenyl ring or substituting whole rings with heterocyclic moieties (Sekkat and Knoll 2002; Bandara and Burdette 2012; Halabieh et al 2004; Tawa et al 2000; 1 3 Vol.:(0123456789)

Results

Conclusion