Synthesis and Structure–Property Relations of a Series of Photochromic Molecular Glasses for Controlled and Efficient Formation of Surface Relief Nanostructures

Abstract

This paper reports on the synthesis and properties of a new series of photochromic molecular glasses and their structure–property relations with respect to a controlled and efficient formation of surface relief nanostructures. The aim of the paper is to establish a correlation between molecular structure, optical susceptibility, and the achievable surface relief heights. The molecular glasses consist of a triphenylamine core and three azobenzene side groups attached via an ester linkage. Structural variations are performed with respect to the substitution at the azobenzene moiety in order to promote a formation of a stable amorphous phase and to tune absorption properties and molecular dynamics. Surface relief gratings (SRGs) and complex surface patterns can easily be inscribed via holographic techniques. The modulation heights are determined with an equation adapted from the theory for thin gratings, and the values are confirmed with AFM measurements. Temperature‐dependent holographic measurements allow for monitoring of SRG build‐up and decay and the stability at elevated temperatures, as well as determination of the glass transition temperature. SRG modulation heights of above 600 nm are achieved. These are the highest values reported for molecular glasses to date. The surface patterns of the molecular glasses are stable enough to be copied in a replica molding process. It is demonstrated that the replica can be used to transfer the surface pattern onto a common thermoplastic polymer.

Refractive-index determination of solids from first- and second-order critical diffraction angles of periodic surface patterns

“…The periodic surface grating was prepared in a way similar to the procedure described in Ref. 13. First a thin film of a photo-addressable molecular glass, a spirobischroman-based 6,6',7,7' tetraester, containing four azobenzene moieties per molecule 14 was prepared by spin-casting from a 7 wt.% THF solution on a glass substrate.…”

High stability of photoinduced merocyanine in naphthopyran‐doped polyvinylpyrrolidone electrospun nanofibers

“…For comparison, the fading curves for compounds 1 , 2 and 3 in solutions, in doped PVP films and in PVP fibers are shown in Fig. , and the kinetic constants can be obtained by fitting the experimental data using the empirical biexponential equation …”

“…Upon light irradiation, the molecular structures and physical properties, such as absorption spectra, are changed. There are many kinds of photochromic units, such as spiropyran, spirooxazine, naphthopyran and azo derivatives . Compared to other photochromic compounds, naphthopyran has advantages of good thermal reversibility, high color density, good resistance to fatigue and large color gamut .…”

Optimization of the photochromic response of photoaddressable polymers with azobenzene-containing molecular glasses

“…The cores (1-6) are all commercially available, except for the triphenylamine core whose synthesis is described elsewhere. [31,32] The azobenzene chromophore a is commercially available with a hydroxy as well as a carboxylic acid chloride function. So it can be coupled to our core compounds which are either carrying up to three carboxylic acid chloride groups or up to four hydroxyl groups.…”