Writing and reading with the longitudinal component of light using carbazole-containing azopolymer thin films

It is well known that azobenzene-containing polymers (azopolymers) are sensitive to the polarization orientation of the illuminating radiation, with the resulting photoisomerization inducing material transfer at both the meso- and macroscale. As a result, azopolymers are efficient and versatile photonic materials, for example, they are used for the fabrication of linear diffraction gratings, including subwavelength gratings, microlens arrays, and spectral filters. Here we propose to use carbazole-containing azopolymer thin films to directly visualize the longitudinal component of the incident laser beam, a crucial task for the realization of 3D structured light yet remaining experimentally challenging. We demonstrate the approach on both scalar and vectorial states of structured light, including higher-order and hybrid cylindrical vector beams. In addition to detection, our results confirm that carbazole-containing azopolymers are a powerful tool material engineering with the longitudinal component of the electric field, particularly to fabricate microstructures with unusual morphologies that differentiate from the total intensity distribution of the writing laser beam.

Evaluation of Local Mechanical and Chemical Properties via AFM as a Tool for Understanding the Formation Mechanism of Pulsed UV Laser-Nanoinduced Patterns on Azo-Naphthalene-Based Polyimide Films

Aromatic polyimides containing side azo-naphthalene groups have been investigated regarding their capacity of generating surface relief gratings (SRGs) under pulsed UV laser irradiation through phase masks, using different fluencies and pulse numbers. The process of the material photo-fluidization and the supramolecular re-organization of the surface were investigated using atomic force microscopy (AFM). At first, an AFM nanoscale topographical analysis of the induced SRGs was performed in terms of morphology and tridimensional amplitude, spatial, hybrid, and functional parameters. Afterward, a nanomechanical characterization of SRGs using an advanced method, namely, AFM PinPoint mode, was performed, where the quantitative nanomechanical properties (i.e., modulus, adhesion, deformation) of the nanostructured azo-polyimide surfaces were acquired with a highly correlated topographic registration. This method proved to be very effective in understanding the formation mechanism of the surface modulations during pulsed UV laser irradiation. Additionally to AFM investigations, confocal Raman measurements and molecular simulations were performed to provide information about structured azo-polyimide chemical composition and macromolecular conformation induced by laser irradiation.

Design of Collective Motions from Synthetic Molecular Switches, Rotors, and Motors

Precise control over molecular movement is of fundamental and practical importance in physics, biology, and chemistry. At nanoscale, the peculiar functioning principles and the synthesis of individual molecular actuators and machines has been the subject of intense investigations and debates over the past 60 years. In this review, we focus on the design of collective motions that are achieved by integrating, in space and time, several or many of these individual mechanical units together. In particular, we provide an in-depth look at the intermolecular couplings used to physically connect a number of artificial mechanically active molecular units such as photochromic molecular switches, nanomachines based on mechanical bonds, molecular rotors, and light-powered rotary motors. We highlight the various functioning principles that can lead to their collective motion at various length scales. We also emphasize how their synchronized, or desynchronized, mechanical behavior can lead to emerging functional properties and to their implementation into new active devices and materials.

Properties of some azo-copolyimide thin films used in the formation of photoinduced surface relief gratings

The patterning of the free standing azo-copolyimide films under different irradiation conditions led to the uniform surface relief gratings.

Thermal stability and optical properties of aromatic polyimides containing side-substituted azobenzene groups

Aromatic azopolyimides based on 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride and aromatic diamines containing substituted azobenzene group have been studied regarding their thermal and photooptical properties. The thermal analysis showed that the decomposition of these polymers takes place in two or three stages. The optical properties of the investigated polymers have been analyzed by transmission and reflectivity measurements within the spectral range of 200–2500 nm. Temperature dependence of absorption coefficient has been found on the basis of “in situ” transmission measurements, during annealing of thin films up to 300°C. It turned out that this process did not change the conjugation of polymer chain but caused a slightly more, irreversible structural disorder.

Preparation and characterization of novel optically active nanostructured poly(amide–imide)s-containing (l)-α-amino acid moieties and azobenzene side groups

A series of optically active poly(amide–imide)s (PAI)s-containing photochromic azobenzene moieties as side groups were synthesized. These chiral polymers were derived from monomers-based (l)-α-amino acids such as alanine, isoleucine, methionine, and phenylalanine. Azo-containing diamine 7 was synthesized from the reaction of 4-aminoazobenzene and 3,5-dinitrobenzoyl chloride, followed by the reduction in dinitro with iron oxide hydroxide catalyst and hydrazine monohydrate. The novel PAIs were prepared by direct polycondensation under green medium. The synthesized PAIs, with inherent viscosities of 0.43–0.85 dL g−1, were obtained in high yields. The structures of them were confirmed by elemental analysis, Fourier transform infrared spectroscopy, and proton and carbon nuclear magnetic resonance spectroscopy techniques. The resulting PAIs were also characterized by x-ray diffraction, field emission scanning electron microscopy, ultraviolet–visible spectroscopy, and thermogravimetric analysis techniques. Morphology probes showed that these PAIs were nanostructured polymers and the particle size was around 40–90 nm.