We report a novel way to modulate the elastic modulus of azobenzene containing liquid crystal networks (LCNs) by exposure to light. The elastic modulus can cycle between different levels by controlling the illumination conditions. Exposing the polymer network to UV light near the trans absorption band of azobenzene gives a small reduction of the glass transition temperature thereby lowering the...

The photoinduced isomerization and thermal back relaxation of an azobenzene-functionalized polymer poly(disperse red 1 acrylate) were investigated at increasing external pressures up to 1.5 GPa inside a diamond-anvil spectroscopic cell. The thermal cis-trans isomerization was monitored by laser pump-probe spectroscopy, which demonstrated an increase in the half-life of the isomerization process...

In this paper the photocontrolled manipulation of solid materials on the surface of a liquid crystalline thin film is described. Three different types of films namely cholesteric liquid crystal (ChLC), compensated nematic liquid crystal (NLC) and nematic LC were used. The rotational and translational manipulation of the microscale solid object was induced by irradiation of light and mode of man...

We describe not only fleeting assembly of photoisomerizable azobenzene-based palladium complexes into microstructured crystalline architectures but also their light-responsive functions. A transformation in the crystalline morphology from two-dimensional (2D) parallelogram-like sheets to three-dimensional (3D) cuboid- or rhombus-like structures was achieved by changing the solvent from tetrahyd...

Light-induced shape transformations represent a fundamental step towards the emergence of adaptive materials exhibiting photomechanical behaviours. Although a range of covalent azobenzene-based photoactive materials has been demonstrated, the use of dynamic photoisomerization in mesostructured soft solids involving non-covalent co-assembly has received little attention. Here we prepare discrete...

The design of stable polymeric micelles that can respond to specific stimuli is crucial for the development of smart micellar nanocarriers that can release their active cargo selectively at the target site, thus diminishing the therapeutic limitations due to non-selective damage to healthy tissues. Here we report the design and synthesis of photo- and enzyme-responsive amphiphilic PEG-dendron h...

The photophysical properties of 6-phenyl-2,2'-bipyridyl platinum(ii) complexes bearing different σ-alkynyl-linked azobenzene ancillary ligands were investigated. These complexes exhibited strong, broad, structureless charge-transfer bands in the visible region, which were red-shifted when the electron-donating ability of the para substituent on the azo-acetylide ligand increased. When excited a...

Aalto University, P.O. Box 11000, FI-00076 Aalto www.aalto.fi Author Jaana Vapaavuori Name of the doctoral dissertation Design of efficient photoresponsive azobenzene materials through supramolecular functionalization Publisher School of Science Unit Department of Applied Physics Series Aalto University publication series DOCTORAL DISSERTATIONS 83/2013 Field of research Materials Physics Manusc...

The photochemical behaviour of functionalised gold nanoparticles (AuNPs) carrying azobenzenethiolate-alkylthiolate monolayers was investigated. Repeated trans-cis and cis-trans isomerisation cycles could be performed in all cases with high efficiency. Reversible photoinduced aggregation was observed when azothiolates with long alkyl spacers (≥C7) were combined with short (C5) alkylthiolate coli...

The reaction of cyclopentanone with cyanoacetylhydrazine gave 2-cyano-2-cyclopentylideneacetohydrazide (1). Treatment of compound 1 with elemental sulphur in the presence of triethylamine afforded 2-amino-5,6-dihydro- -4H-cyclopenta[b]thiophene-3-carbohydrazide (2), which in-turn formed the corresponding intermediate diazonium salt. The latter was coupled with either ethyl cyanoacetate or ethyl...