Abstract
We present investigation of optical and photochromic properties as well as of surface quality of thin films of novel methacrylic polymers with 8-hydroxyquinoline azo-dyes in side-chain. Additionally, thermal stability of polymer powders was examined and their glass transition temperature was determined. Optical properties (extinction coefficient and refractive index) were determined by spectroscopic ellipsometry (SE) combined with absorbance measurements. Photoresponsive behavior was investigated by determination of photoisomerization rates under irradiation with unpolarized 365 nm light, as well as by conduction of holographic grating inscription experiment. Thin film quality was determined by atomic force microscopy (AFM) measurements. Thermal analysis was performed by thermogravimetric (TG), derivative thermogravimetric (DTG) and differential scanning calorimetry (DSC) measurements. We found that optical properties as well as photoisomerization rates of investigated polymers are dependent on the substituent in the para position of the phenyl ring. Surface relief grating inscription was successfully generated only for materials with chromophores containing dimethylamino (N(CH3)2) and methyl (CH3) substituents, but all materials exhibited birefringence grating in the bulk. Surface of most thin films was very smooth, but its quality was impaired by neutral (H) as well as carboxyl (COOH) substituent. Thermal stability of copolymers with side-chain chromophores was improved compared to pure poly(methyl methacrylate) (PMMA).
Highlights
Azobenzene derivatives are a widely studied class of dyes due to their spectroscopic, photochromic and non-linear optical properties as well as photostability [1,2,3], which make them attractive for use in optical limiters, optical signal processing, optical data storage and holography [1,2,3,4,5]
We focused on the influence of different electron donating and electron withdrawing substituents in the para position of the phenyl ring on the surface quality of the films measured with atomic force microscopy (AFM), and on optical constants determined by spectroscopic ellipsometry (SE) together with absorbance measurements
Quality of the prepared thin films was studied with AFM measurements
Summary
Azobenzene derivatives are a widely studied class of dyes due to their spectroscopic, photochromic and non-linear optical properties as well as photostability [1,2,3], which make them attractive for use in optical limiters, optical signal processing, optical data storage and holography [1,2,3,4,5]. Azobenzene is composed of two phenyl rings linked by an azo (-N=N-) bridge [1,3]. Azobenzene can appear in two isomeric forms: Stable trans and metastable cis [1,3,7], and it can change its conformation due to reversible isomerization. This reaction can be induced by irradiation with light of the proper wavelength, or it can happen spontaneously in the dark (cis–trans back reaction) [1]. When the molecule change its shape from trans to cis form, the π-π* band becomes weaker and shifts batochromically, while the n-π* band becomes more intense [1,3,8]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
