Photoinduced shape deformation of colloidal spheres made of an amphiphilic azo polymer has been demonstrated in this work. The polymer contains the donor-and-acceptor-type azobenzene chromophores and can form uniform colloidal spheres by dropwise adding water into its THF solution. When the colloidal spheres obtained were exposed to the interfering p-polarized Ar+ laser beams (150 mW/cm2), the colloidal spheres changed to prolates (i.e., "rugby-balls"), "spindles", and finally "rods", depending on the irradiation times. The elongated direction of the spheres was observed to be the same as the polarization direction of the laser beam. The average major-to-minor ratio of the ellipsoids could be easily adjusted by controlling the irradiation time. The deformation effect observed in this work can offer a new way to prepare nonspherical colloids from colloidal spheres and will shed new light on the correlation between the photodriven shape deformation and photoinduced surface relief gratings for the same type of polymers.

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A gas sensing method based on quartz-tuning-fork enhanced photothermal spectroscopy (QEPTS) is reported in this paper. Unlike usually used thermally sensitive elements, a sharply resonant quartz-tuning-fork with the capability of enhanced mechanical resonance was used to amplify the photothermal signal level. Acetylene (C 2 H 2) detection was used to verify the QEPTS sensor performance. The measured results indicate a minimum detection limit (MDL) of 718 ppb and a normalized noise equivalent absorption coefficient (NNEA) of 7.63 × 10 −9 cm −1 W/√Hz. This performance demonstrates that QEPTS can be an ultra-high sensitive technique for gas detection and shows superiority when compared to usually used methods of tunable diode laser absorption spectroscopy (TDLAS) and quartzenhanced photoacoustic spectroscopy (QEPAS). Furthermore, when compared to an optical detector, especially a costly mercury cadmium telluride (MCT) detector with cryogenic cooling used in TDLAS, a quartz-tuning-fork is much cheap and tiny. Besides, compared to the QEPAS technique, QEPTS is a non-contact measurement technique and therefore can be used for standoff and remote trace gas detection.

A simple electrostatic self-assembly technique was used to fabricate a photo-switched azobenzene monolayer, on which superhydrophobicity and a large reversible CA change could be realized.

This work shows that a linearly polarized Ar+ laser single-beam irradiation can cause stretching deformation of azo polymer colloidal spheres along the polarization direction of the laser beam. An epoxy-based polymer, containing 4-amino-4'-carboxyazobenzene at each repeat unit, was used to construct the colloidal spheres. The colloidal spheres were prepared by gradual hydrophobic aggregation of the polymeric chains in a THF/H2O dispersion medium, which was induced by a steady increase in the water content. When the obtained colloidal spheres were exposed to the spatially filtered and collimated Ar+ laser beam (488 nm, 150 mW/cm2), the colloids were stretched along the polarization direction of the laser beam. In the testing period (20 min), the colloids were deformed continuously as the irradiation time increased. When 2D close-packed arrays of the colloidal spheres were irradiated by the polarized laser single-beam, the colloidal spheres were all uniformly stretched along the polarization direction of the laser beam. On the contrary, when the arrays were irradiated by the interfering p-polarized laser beams, only the colloidal spheres in the bright regions of the interference pattern were significantly deformed.

In this article, we describe the fabrication of azobenzene-containing supramolecular side-chain polymer films based on hydrogen bonds, on which surface relief gratings can be laser-induced. The supramolecular polymer side-chain is formed by attaching different azobenzene-type compounds to poly(4-vinylpyridine) through hydrogen bonding, thus allowing for tuning the content and kind of the azobenzene derivatives easily and avoiding the tedious synthetic work. It is found that such an azobenzene-containing supramolecular side-chain polymer can form nice films by the spin-coating method for surface relief gratings, and moreover, a large surface modulation depth of 312 nm can be observed. We anticipate that this research provides a type of materials for surface relief gratings. In closing, we have provided a new approach for fabricating surface relief gratings employing hydrogen-bonded supramolecular side-chain azo polymers.

Summary: A soft‐lithographic imprinting approach to fabricate super‐hydrophobic surfaces has been developed in this work. In this process, fresh lotus leaves were used as masters and PDMS stamps were prepared by replica molding against the lotus‐leaf surfaces. By using the stamps and an epoxy‐based azo polymer solution as “ink”, the mimicked lotus‐leaf surfaces made of the polymer were fabricated by pressing the featured faces of the stamps against “inked” substrates and drying under a proper condition after peeling off the stamps. The lotus‐leaf‐like surfaces show super‐hydrophobic characteristics with the water contact angle higher than 150° and contact angle hysteresis less than 3°.SEM images of lotus‐leaf‐like papillary structures on the imprinted surface.magnified imageSEM images of lotus‐leaf‐like papillary structures on the imprinted surface.

A novel class of photochromic materials based on polar azo derivatives containing functionalized biphenyl substituents has been synthesized. Once melt and cooled, these compounds formed amorphous transparent monomeric materials whose glass transition temperatures depend mainly on the bulkiness of the biphenyl substituent; by contrast, a change in polarity, evidenced by absorption spectroscopy and DFT calculations, exerts insignificant influence. Photoisomerization of the azo groups occurred both in solution and thin films; the rate constants of the thermal back-relaxation in both media increase with compound polarity. Photoconversion yields display smaller values in solid state than in solution, due to more packed surroundings; surprisingly, they increase substantially with the monomer bulkiness, despite raising T g s. Comparative dynamic surface relief grating writings and AFM surface modulation measurements of irradiated thin films showed that the efficiency of the writing process improves dramatically for glasses consisting of more hindered and less polar compounds with a 4-and 2-fold increase in the diffraction efficiency and peak-to-trough amplitude, respectively. Such results highly contrast with those obtained in polymer matrices, where competitive polymer chain reorganization occurs. Free volume enhancement upon back-and-forth photoisomerization of bulky photochromes, facilitating the azo photoisomerization, has been put forward to explain these results.