Search

The intensive use of fossil fuels has profound impacts on all ecosystems, primarily contributing to global warming through greenhouse gas emissions. To mitigate these impacts, alternative energy sources like hydrogen are crucial. In this study, azo cross‐linked polymer with 4‐aminophenyl sulfone and resorcinol were synthesized by a green synthesis method. The polymer was extensively characterized by Fourier‐transform infrared spectroscopy, Brunner‐Emmett‐Teller analysis, thermogravimetric analysis, and scanning electron microscopy‐energy dispersive x‐ray spectroscopy analyses. Subsequently, the catalytic performance of the polymer in hydrogen production from NaBH4 via methanolysis was investigated. At this stage, the parameters affecting hydrogen production (catalyst and NaBH4 amounts, MeOH volume and temperature) were systematically studied to determine optimum conditions. The maximum HGR values of the polymer was 13,100 and 27,000 mL min−1 gcat−1 at 30 and 60°C, respectively and its activation energy was 10.45 kJ mol−1. After optimization, the reusability of azo polymer was tested with 5 cycles. The theoretical volume of hydrogen was produced in all 5 cycles. But with each cycle, the hydrogen production time increased. The main purpose of this study was to demonstrate novel azo‐linked polymers with high catalytic activity in hydrogen production. The results revealed significant potential of the polymer for hydrogen generation. Overall, this research highlights the promising role of azo cross‐linked polymers as effective catalysts for hydrogen production, offering new perspectives and pathways towards sustainable energy solutions. [ABSTRACT FROM AUTHOR]

In this paper, a class of porous organic polymers (POPs) of p -hydroxy azobenzene with a mesoporous structure was designed and synthesized by a –N N– coupling reaction of tetraamino-metal phthalocyanine (MTAPc, where M = Co, Ni or Cu) with hydroquinone (namely Azo-MHQ, where M = Co, Ni or Cu). The Azo-MHQ materials possessed good thermal stabilities, excellent dispersibilities in water, polar and non-polar organic solvents, as well as excellent chemical stabilities. Among them, Azo-CuHQ showed an outstanding iodine trapping ability in an iodine solution and vapor with saturated adsorption capacities of 1347.47 mg g−1 and 118 wt%. In addition, Azo-CuHQ also showed a high adsorption capacity for methylene blue (MB) with the adsorption amount of 191.21 mg g−1. Furthermore, by loading Azo-CuHQ onto polyethersulfone (PES) membrane, the water permeability of the obtained membranes reached 147.03 L m−2 h−1 bar−1, and the retention rate of Ag in a very low concentration solution of 20 ppm was 56.8 %. Additionally, a thorough analysis of the Azo-CuHQ adsorption and separation mechanism was conducted. A novel approach to the design and synthesis of a class of materials with multifunctional adsorption and separation capabilities is presented in this research. [Display omitted] • Low-temperature synthesis of Azo-MHQ in an aqueous solution is an effective method. • Azo-CuHQ exhibits an excellent adsorption capability for iodine molecule. • Azo-CuHQ can preferentially adsorb MB via hydrogen bonds. • By loading Azo-CuHQ onto PES, the Ag retention rate is 56.80 %. [ABSTRACT FROM AUTHOR]

Surface‐relief‐gratings (SRGs) of azo polymers and azo molecular glasses have attracted considerable interest for their erasable and reconfigurable characteristics. Herein, the optical erasure of soft‐lithographically duplicated SRGs of an azo polymer (BP‐AZ‐CN) and an azo molecular glass (IAC‐4) is investigated to tackle a long‐standing problem from “memory” effect existing in optically inscribed SRGs. The optical erasure is performed by single laser beam irradiation at wavelength of 488 nm with different polarizations, and the erasing behavior is thoroughly investigated by real‐time diffraction efficiency measurement and atomic force microscopy (AFM) observation. Showing no obvious dependence on the light polarizations, the optical erasure of IAC‐4 grating is a relatively fast process, and the original one can be completely erased and recreated. In contrast, the erasure of BP‐AZ‐CN grating is not only much slower, but also strongly correlated with the light polarizations. Upon the p‐polarized light irradiation, the grating profiles are substantially distorted during the erasure with a significant difference in that of the s‐polarized light irradiation. The gratings cannot be completely erased by the lights with all the polarizations. The erasure behavior is found to be determined by the effects of surface tension and mass transfer along the light polarization direction to different extents.

Covalent connected fluorescent probe is often effective, but sometimes it is inevitable to adopt complex molecular design and tedious synthesis process. With the advantages of relatively simple operability and widespread generality, noncovalent strategy is gradually considered an ideal choice to solve this dilemma. In this work, an enzyme‐activatable noncovalent fluorescent probe based on water soluble positively charged azobenzene containing poly(ethylene oxide)‐b‐poly[2‐(methacryloyloxy)‐N,N,N‐trimethylethan‐1‐aminium iodide‐co‐(4‐(4‐dimethylamino)phenylazophenyl methacrylate)] (PEG‐b‐PQDMA‐co‐PAZOMA) and negatively charged 3,3′‐(((2‐(4‐(2,2‐dicyano‐1‐phenylvinyl)phenyl)‐2‐phenylethene‐1,1‐diyl)bis(4,1‐phenylene))bis(oxy))bis(propane‐1‐sulfonate) (TPE‐2SO3−) is reported. Due to the fluorescence resonance energy transfer process from aggregates induced emission donor to azobenzene acceptor, this probe is nearly non‐emissive. After the reduction of azo bond by azoreductase under hypoxic condition, the probe emits strong fluorescence with long emission wavelength, realizing efficient off–on property. In addition, the cleavage of the azobenzene do not show influence on the morphology of the nano sized self‐assemblies. [ABSTRACT FROM AUTHOR]

Here, we will show photo-induced supramolecular chirality in thin films of achiral amorphous polymers with azo groups in their side-chain. A matter of particular interest is the effect of various film thicknesses on azimuthal rotation and ellipticity of incident/transmitted polarized light. Furthermore, we investigated the temporal stability of inscribed chirality. By polarimetric measurements, we found out that the azimuthal rotation gets higher with layer thickness. In this scope, we were able to measure a very high azimuthal rotation of Δψ/d=112.5∘/μm. The inscribed chirality was stable for several days. Furthermore, we investigated the time-resolved behavior of incident and transmitted polarization ellipticities for various thicknesses. The time dependency may be explained by a two-step process: (1) fast trans-cis-isomerization resulting in photo-orientation and (2) slow photo-induced mass flow.

New photochromic polymethacrylates with different spacer length having azobenzene side groups and lateral methyl substituents were synthesized. The phase behavior of polymethacrylates and their photooptical properties were studied and compared with unsubstituted analogues. It is shown that an introduction of lateral methyl substituents results in almost complete suppression of liquid crystalline (LC) phase formation and strong decrease of photoinduced dichroism values. It is found that rates of the photoinduced E‐Z isomerization and back thermal Z‐E isomerization are almost independent on spacer lengths. Due to the presence of lateral substituents, the photoinduced azobenzene Z‐form shows remarkable long lifetime, and back thermal conversion at room temperature takes more than 10 days. Specific peculiarities of the photoorientation process in polymer films under the polarized UV and visible light action were studied and their mechanism is suggested. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1337–1342 [ABSTRACT FROM AUTHOR]

Azobenzene-containing block copolymers have been previously developed as light-induced reworkable adhesives that can undergo repeatable bonding/debonding on demand, based on photoisomerization of the azobenzene moiety and concomitant softening/hardening of the azo polymer block. For practical use, the applicability of such adhesives to various types of substrates is important and is thus studied as one of their most fundamental properties in this work. Ultraviolet (UV)-transparent acrylic resin as well as non-transparent polycarbonate resin, polyethylene ones, and metallic aluminum substrates are utilized as substrates. UV-transparent acrylic resin is used as one of two substrates to investigate the photoisomerization process. The bonding/debonding process is successful for these substrates, and single lap shear tests show typical adhesion strengths of 1.5-2.0 MPa for the substrates investigated. UV irradiation induced a decrease in the adhesion strength to 0.03 MPa irrespective of the substrate type, indicating that the mechanism of the detachability is flow of the softened adhesive. Facile removal of the residual adhesive on the substrate is successfully demonstrated after detachment without any damage to the substrates by wiping the substrate with laboratory-grade disposable wipes wet with ethanol. [ABSTRACT FROM AUTHOR]

We previously reported that ABA‐type triblock copolymers with azobenzene‐containing terminal blocks can be utilized as a light‐induced reworkable adhesive that enables repeatable bonding and debonding on demand. The reworkability was based on the photoisomerization of the azobenzene moiety and concomitant softening and hardening of the azo blocks. Our aim in this study is to investigate the effect of the composition, molecular weight, and block copolymer architectures on the reworkable adhesive properties. For this purpose, we prepared AB diblock, ABA triblock, and 4‐arm (AB)4 star‐block copolymers consisting of polymethacrylates bearing an azobenzene moiety (A block) and 2‐ethylhexyl (B block) side chains and performed adhesion tests by using these block copolymers. As a result, among the ABA block copolymers with varied compositions and molecular weights, the ABA triblock copolymers with an azo block content of about 50 wt % and relatively low molecular weight could achieve an appropriate balance between high adhesion strength and low residual adhesion strength upon UV irradiation. Furthermore, the 4‐arm star‐block structure not only enhances the adhesion strength, but also maintains low residual adhesion strength when exposed to UV irradiation. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 806–813 Various types of azobenzene‐containing block copolymers, such as AB diblock, ABA triblock, and 4‐arm (AB)4 star‐block copolymers, can be utilized as reworkable adhesives that enable bonding/debonding by light irradiations. Among them, the star‐block structure enhances the adhesion strength, as well as maintaining low residual adhesion strength when exposed to UV irradiation. [ABSTRACT FROM AUTHOR]

ABSTRACT: A novel series of hard‐soft‐hard triblock azo‐copolymers (TBCs) composed of poly(2‐[2‐(4‐cyano‐azobenzene‐4‐oxy)ethylene‐oxy]ethyl methacrylate) (PCEAMA), poly(methyl methacrylate) (PMMA) and poly(p‐dodecylphenyl‐N‐acrylamide) (PDOPAM) were synthesized by employing reversible addition‐fragmentation chain transfer polymerization. Chemical structures and molecular weights were characterized by 1H nuclear magnetic resonance (NMR) and gel permeation chromatography (GPC). Thermal behavior, mesophase, photochemistry and morphology were investigated using differential scanning calorimetry (DSC), optical polarizing microscopy (OPM), ultraviolet–visible spectrophotometry (UV–vis), atomic force microscopy (AFM) and grazing‐incidence small‐angle X‐ray scattering (GISAXS). Kinetic studies confirmed characteristic of controlled/living radical polymerization with low polydispersities (≤1.40). TBCs manifested both endothermic and exothermic transition peaks assigned to smectic to nematic, nematic to smectic, and smectic‐A to smectic‐C phases. TBCs having hight azo fractions of 39 and 34 wt % revealed textures of smectic phase whereas TBC possessing 30 wt % of azo content exhibited poor texture, suggesting nematic phase. Regarding TBC with low azo ratio (25 wt %), neither mesophase texture was found. All TBCs showed photoresponsive behavior under UV–vis irradiation or thermal relaxation. TBC‐1 with PCAEMA (39 wt %), PMMA (40 wt %) and PDOPAM (21 wt %) generated a mixture of cylinder and lamellar nanostructures compared to TBC‐2 and TBC‐3 which formed lamellae. However, TBC‐4 having the highest PDOPAM fraction (50 wt %) produced hexagonal cylindrical nanostructure. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018, 56, 1617–1629 [ABSTRACT FROM AUTHOR]

Mechanical properties of two amorphous azo polymers were characterized in tensile measurements and correlated with photoinduced behaviour of the materials observed upon irradiation with blue light of moderate intensity. Side-chain azobenzene poly(amide imide)s capable of forming high-quality free-standing layers of a large area and thickness of a few micrometers were chosen for the investigations. High Young's modulus of ca. 2 GPa and yield stress of the order of 30 MPa were found for the materials. Photoinduced birefringence measurements evidenced efficient chromophore orientation in both polymers, while polymer mass transport upon illumination with interference pattern was hardly observed. Nevertheless, subtle periodic changes in the surface topography of the films after irradiation with right- and left-handed circularly polarized beams suggested that opto-mechanical stress reached the value of a few tens of MPa, i.e., the minimum value needed for inducing plastic deformations in the studied azo polymers. [ABSTRACT FROM AUTHOR]

Azo waveguide polymers are of particular interest in the design of materials for applications in optical switch. The aim of this contribution was the synthesis and thermo-optic waveguide switch properties of azo biphenyl polyurethanes. A series of monomers and azo biphenyl polyurethanes (Azo BPU1 and Azo BPU2) were synthesized and characterized by FT-IR, UV–Vis spectroscopy and 1 H NMR. The physical and mechanical properties of thin polymer films were measured. The refractive index and thermo-optic coefficient (d n /d T ) of polymer films were investigated for TE (transversal electric) polarizations by ATR technique. The transmission loss of film was measured using the Charge Coupled Device digital imaging devices. The results showed the Azo BPU2 containing chiral azobenzene chromophore had higher d n /d T and lower transmission loss. Subsequently, a 1 × 2 Y-branch and 2 × 2 Mach-Zehnder optical switches based on the prepared polymers were designed and simulated. The results showed that the power consumption of all switches was less than 1.0 mW. Compared with 1 × 2 Y-branch optical switch, the 2 × 2 Mach-Zehnder optical switches based on the same polymer have the faster response time, which were about only 1.2 and 2.0 ms, respectively. [ABSTRACT FROM AUTHOR]

ABSTRACT This work evaluates the inscription of surface relief gratings (SRG) in a series of epoxy-azo prepolymers and networks, both based on the same azo chromophore. Variables such as matrix structure (thermoplastic/thermoset), film thickness, exposure time, power of the incident laser beam, and content of azobenzene were analyzed on the final modulation depth of the gratings. The main goal of the article is to achieve the efficient formation of SRGs on crosslinked azopolymer films in a single step, in a reasonable time, and to a significant extent. The progressive erasure of the obtained structures with increasing temperature showed that part of the photoinduced information remained encoded in the material: as the relief partially relaxed above the glass transition temperature of the bulk material (116 °C) and up to 200 °C, its modulation remained in about one third of the initial height, and did not completely disappear. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1542-1552 [ABSTRACT FROM AUTHOR]

We report on a series of photoresponsive azobenzene poly(ester imide)s thermally converted from their precursor poly(ester amic acid)s. Thermal properties as well as ability for efficient photoinduced chromophore orientation and polymer mass transport under linearly polarized blue irradiation were investigated, focusing on the effect of azo chromophore location within polymer chain. The amount of chromophore alignment studied in the experiment on photoinduced birefringence differed by a factor of l.5 between the materials. Despite the fact that the generated birefringence was of the same order of magnitude, very large differences in efficiency of surface relief grating formation were seen. Specific features of photoresponsive behaviour of the polymers were shown to correlate with the presence or the absence of intrachain C H⋯π interaction between azobenzene hydrogen and aromatic imide structure, which was revealed by density functional theory (DFT) calculations. Advantageous chromophore location next to the imide groups for effective light-driven processes was shown. [ABSTRACT FROM AUTHOR]

Properties such as friction, wettability and visual impact of polymer coatings are influenced by the surface topography. Therefore, control of the surface structure is of eminent importance to tuning its function. Photochromic azobenzene-containing polymers are an appealing class of coatings of which the surface topography is controllable by light. The topographies form without the use of a solvent, and can be designed to remain static or have dynamic properties, that is, be capable of reversibly switching between different states. The topographical changes can be induced by using linear azo polymers to produce surface-relief gratings. With the ability to address specific regions, interference patterns can imprint a variety of structures. These topographies can be used for nanopatterning, lithography or diffractive optics. For cross-linked polymer networks containing azobenzene moieties, the coatings can form topographies that disappear as soon as the light trigger is switched off. This allows the use of topography-forming coatings in a wide range of applications, ranging from optics to self-cleaning, robotics or haptics. [ABSTRACT FROM AUTHOR]

ABSTRACT Functional polystyrene (PS) crosslinked microbeads were developed by dispersion polymerization as fluorescent molecularly imprinted polymers (MIPs) having cavities with specific recognition sites. The functional azobenzene molecule modified with pyridine was self-assembled with Pyrenebutyric acid (template molecules), and introduced during the second stage of dispersion polymerization of polystyrene. The template molecule was removed from MIP by Soxhlet using acetonitrile as solvent. Non imprinted polymer (NIP) having no template was also synthesized for comparative study. Fluorescence spectroscopy could be used as a tool to derive insight into the location of the template molecules on the MIP or NIP. The template molecules were adsorbed on the surface of the NIPs during binding studies, which was evidenced from the pyrene excimeric emission observed at 440 nm. The template binding efficiency of the NIPs were much lower compared to MIPs. Pyrene emission from MIP upon rebinding showed typical monomeric emission in the 375-395 nm range, confirming its location in isolated cavities. In rebinding studies of the template molecules, the MIPs selectively took up the template for which the cavity was designed, which demonstrated their selectivity towards template molecules. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017, 55, 1558-1565 [ABSTRACT FROM AUTHOR]

Recording media for polarization holography have been created using copolymers of azobenzene monomers and octyl methacrylate, and the electrophysical and information properties of these materials have been studied. The increase in the diffraction efficiency of holograms in an external electric field has been found to be faster in copolymers with an azo chromophore possessing a larger dipole moment. [ABSTRACT FROM AUTHOR]

Segmented polyurethanes containing azo aromatic groups in the main chain were synthesized by reaction of 3,3'-azobis(6-hydroxybenzoic acid) (ABHB), 5-[4-(hydroxyphenyl)azo] salicylic acid (HPAS), and 5-[1-hydroxynaphthyl)azo] salicylic acid (HNAS) with hexamethylenediisocyanate (HDI). All synthesized monomers and polymers were characterized by elemental analysis, FTIR, 1H-NMR spectra, TGA and DSC analysis. All the synthesized azo polymers showed good thermal stability and the onset decomposition temperature of all these polymers was found to be above 195 ºC under nitrogen atmosphere.The release of 5-ASA under physiological conditions (pH = 7.8 and pH = 1.5) was investigated at body temperature (37 ºC). The release rate of 5-ASA increased with increasing pH (i.e., 7.8 > 1.5).

ABSTRACT Long-term stable holographic volume gratings in azobenzene-containing films have potential applications as forgery-proof security features or in holographic data storage. However, azobenzene-based polymer systems often lack sufficiently high writing speeds. Here, an approach to improve the holographic writing performance of photo-orientable azobenzene-containing polymers by blending with azobenzene molecular glasses is presented. The molecular glass enhances the photo-plastification effect and, consequently, the writing speed. This concept of improving the holographic performance of photo-orientable azobenzene polymers with azobenzene molecular glasses is demonstrated with a homopolymer and two block copolymers. In the azobenzene homopolymer, an addition of 10 wt % of the molecular glass leads to a doubling of the writing speed. Simultaneously, the long-term stability of inscribed gratings is maintained. In case of the block copolymers, the molecular glass is present in the polystyrene matrix and accumulates in the azobenzene minority phase. Adding 5-10 wt % of molecular glass improves the writing speed of the azobenzene block copolymer by a factor of 3-4. An addition of 15 wt % of molecular glass to the block copolymer containing azobenzene and nonphotoactive mesogenic side groups reduces the writing time by a factor of 15 and the long-term stability of the gratings is retained. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2110-2117 [ABSTRACT FROM AUTHOR]

ABSTRACT A new aggregation-induced emission (AIE) active polymer (PS-TPE) with high tetraphenylethene (TPE) loading density was synthesized. The synthesized polymer showed significant AIE properties, good solubility and high thermal stability. Soft-lithographic contact printing process by using photoinduced surface relief structures on azo polymer film as masters and duplicated PDMS elastomer as stamps was used to fabricate fluorescent PS-TPE patterns. Various fluorescent structures with high contrast including surface relief gratings, periodically dotted patterns, and quasi-crystal structures can be easily fabricated through this approach. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1838-1845 [ABSTRACT FROM AUTHOR]

ABSTRACT Two photosensitive chiral liquid crystalline azobenzene-containing polymethacrylates having different length of flexible spacer connecting chromophores with backbone were synthesized and their phase behavior and photo-optical properties were studied. Both polymers consist of lateral methyl substituents in ortho-position of azobenzene chromophores providing high photosensitivity even in red spectral region as well as high thermal stability of photoinduced Z-form of azobenzene chromophores. It is shown, that smectic phase (SmA*) formation in films of polymer with longer spacer predetermines its quite unusual spectral response to UV and subsequent visible light actions. The SmA* phase promotes spontaneous homeotropic alignment of azobenzene chromophores in polymer films. UV-irradiation induces not only E-Z isomerization but also results in disruption of homeotropic alignment, whereas subsequent visible light action enables to obtain films with the low degree of chromophores orientation. The photo-orientation phenomena under the action of polarized light of different wavelength on polymer films were studied. The possibility of using red polarized light of moderate intensity for optical photorecording on polymer films is demonstrated. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2962-2970 [ABSTRACT FROM AUTHOR]

ABSTRACT Photoorientation and reorientation processes induced by illumination of the samples with oppositely directed polarized light and by the thermal treatment were studied for the films of triblock copolymer pAzo10-b-pPhM80-b-pAzo10 consisting of a nematic phenyl benzoate сentral sub-block (PhM, DP = 80) with two terminal smectic azobenzene sub-blocks (Azo, DP = 10). For amorphized films of triblock copolymer, illumination with polarized light ( λ = 546 nm) is shown to be by orientation of only Azo-containing groups, but upon following annealing of the film, PhM groups are adjusted to the orientation of Azo fragments. It was found, that the subsequent illumination of the block copolymer sample with oppositely directed polarized light changes the orientation of azobenzene groups, while the orientation of phenyl benzoate groups is remained unchanged. Thus, the cyclic illumination of the triblock copolymer samples by the linear polarized light and subsequent thermal treatment make it possible to control and fix orientation of azobenzene and phenyl benzoate groups located in different sub-blocks in the desired and independent manner. The comparison of these results with the data on random p(Azo7- ran-PhM30) copolymer of the similar composition revealed, that in the random copolymer, both Azo and PhM mesogenic groups are involved in the orientational cooperative process regardless of films process treatment. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1602-1611 [ABSTRACT FROM AUTHOR]

It is of great fundamental and practical significance to endow Janus particles with various field-responsive properties. In this study, a new strategy with a wide range of application possibilities is developed to fabricate JPs composed of a methacrylate-based azo polymer, polystyrene, and Fe3O4 nanoparticles. The JPs are obtained through microphase separation in a confined volume of the dispersed droplets. The azo polymer and PS are incorporated in JPs in a core-compartmentalized manner, and Fe3O4 are proved to exist in the azo polymer phase. The JPs show responsive movement in the magnetic field and can be easily oriented with the help of the field. By variation of the intersection angle between the particle symmetrical axis and the polarization direction of the linearly polarized laser beam, different deformation modes are feasibly achieved for the JPs. By exploiting the dual-responsive properties, JPs with designed shapes can be fabricated by exposing the JPs to linearly polarized light. [ABSTRACT FROM AUTHOR]

Here, a simple combined strategy of surface wrinkling with visible light irradiation to fabricate well tunable hierarchical surface patterns on azo-containing multilayer films is reported. The key to tailor surface patterns is to introduce a photosensitive poly(disperse orange 3) intermediate layer into the film/substrate wrinkling system, in which the modulus decrease is induced by the reversible photoisomerization. The existence of a photoinert top layer prevents the photoisomerization-induced stress release in the intermediate layer to some extent. Consequently, the as-formed wrinkling patterns can be modulated over a large area by light irradiation. Interestingly, in the case of selective exposure, the wrinkle wavelength in the exposed region decreases, while the wrinkles in the unexposed region are evolved into highly oriented wrinkles with the orientation perpendicular to the exposed/unexposed boundary. Compared with traditional single layer-based film/substrate systems, the multilayer system consisting of the photosensitive intermediate layer offers unprecedented advantages in the patterning controllability/universality. As demonstrated here, this simple and versatile strategy can be conveniently extended to functional multilayer systems for the creation of prescribed hierarchical surface patterns with optically tailored microstructures. [ABSTRACT FROM AUTHOR]

ABSTRACT We report novel liquid crystalline (LC) polymers containing pendant azobenzene moieties with n-dodecyl substituents and ethyleneoxy spacers of different lengths and describe their selective detection behaviors to alkali metal ions. The new azopolymers produce homogenous smectic phases with a typical fan-shaped texture. UV-Vis and 1H NMR studies confirm that the azopolymers selectively bind to Li+ and Na+, but do not complex with K+, Ba2+, Mg2+, or Ca2+. Both the ethyleneoxy spacer and azobenzene units participate in binding to Li+ and Na+ cations in solution. Interestingly, after formation of the complexed structure, the ratio of cis to trans conformer is considerably increased suggesting stronger interactions of the cis conformer with alkali metal ions. Irradiation of the complexed structure with 365 nm UV induces conversion of the uncomplexed trans to the cis. These findings suggest a great potential of the LC azopolymers as selective sensors or separation membranes for alkali metal ions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1713-1723 [ABSTRACT FROM AUTHOR]

Hyperbranched poly(N-isopropylacrylamide)s (HBPNIPAMs) end-capped with different azobenzene chromophores (HBPNIPAM-Azo-OC3H7, HBPNIPAM-Azo-OCH3, HBPNIPAM-Azo, and HBPNIPAM-Azo-COOH) were successfully synthesized by atom transfer radical polymerization (ATRP) of N-isopropylacrylamide using different azobenzene-functional initiators. All HBPNIPAMs showed a similar highly branched structure, similar content of azobenzene chromophores, and similar absolute weight/average molecular weight. The different azobenzene structures at the end of the HBPNIPAMs exhibited reversible trans-cis-trans isomerization behavior under alternating UV and Vis irradiation, which lowered the critical solution temperature (LCST) due to different self-assembling behaviors. The spherical aggregates of HBPNIPAM-Azo-OC3H7 and HBPNIPAM-Azo-OCH3 containing hydrophobic para substituents either changed to bigger nanorods or increased in number, leading to a change in LCST of -2.0 and -1.0 °C, respectively, after UV irradiation. However, the unimolecular aggregates of HBPNIPAM-Azo were unchanged, while the unstable multimolecular particles of HBPNIPAM-Azo-COOH end-capped with strongly polar carboxyl groups partly dissociated to form a greater number of unimolecular aggregates and led to an LCST increase of 1.0 °C. [ABSTRACT FROM AUTHOR]

Properties such as friction, wettability and visual impact of polymer coatings are influenced by the surface topography. Therefore, control of the surface structure is of eminent importance to tuning its function. Photochromic azobenzene-containing polymers are an appealing class of coatings of which the surface topography is controllable by light. The topographies form without the use of a solvent, and can be designed to remain static or have dynamic properties, that is, be capable of reversibly switching between different states. The topographical changes can be induced by using linear azo polymers to produce surface-relief gratings. With the ability to address specific regions, interference patterns can imprint a variety of structures. These topographies can be used for nanopatterning, lithography or diffractive optics. For cross-linked polymer networks containing azobenzene moieties, the coatings can form topographies that disappear as soon as the light trigger is switched off. This allows the use of topography-forming coatings in a wide range of applications, ranging from optics to self-cleaning, robotics or haptics.

ABSTRACT A novel visible light responsive random copolymer consisting of hydrophobic azobenzene-containing acrylate units and hydrophilic acrylic acid units has been prepared. The azobenzene molecule bearing methoxy groups at all four ortho positions is readily synthesized by one-step conversion of diazotization. The as-prepared polymer can self-assemble into nanoparticles in water due to its amphiphilic nature. The tetra- o-methoxy-substituted azobenzene-functionalized polymer can exhibit the trans-to- cis photoswitching under the irradiation with green light of 520 nm and the cis-to- trans photoswitching under the irradiation with blue light of 420 nm in both solution and aggregate state. The morphologies of the self-assembled nanoparticles are revealed by TEM and DLS. The controlled release of loaded molecules from the nanoparticles can be realized by adjusting pH value since the copolymer possesses pH responsive acrylic acid groups. The fluorescence of loaded Nile Red in the nanoparticles can be tuned upon the visible light irradiation. The reversible photoswitching of the azobenzene-functionalized polymer under visible light may endow the polymer with wide applications without using ultraviolet light at all. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 2768-2775 [ABSTRACT FROM AUTHOR]

Commercially available 4,4′-methylene bis(phenyl isocyanate), when copolymerized with the atropisomeric monomer S-(-)-1,1′-binaphthyl-2,2′-diamine, provides convenient access to urea-linked polymers that exhibit exceptional levels of solvent-dependent chiroptical behavior. The use of different solvent media affords a high degree of control over both the sign and magnitude of the optical rotations that are ultimately displayed by these conformationally dynamic systems. The polarity of the solvent environment appears to play a role in shaping polymer responses. A number of related poly(urea-amide) constructs fitted with azobenzene backbone segments are also sensitive to the application of light and heat, ultimately providing for highly adaptive material systems with chiroptical outputs that can be dynamically modulated in real-time by a combination of different input signals. [ABSTRACT FROM AUTHOR]

Light induced effects on rod and bent shaped liquid crystals with azobenzene moiety were investigated using UV/Vis spectrophotometer. Study revealed that shape of the structure influenced their relaxation behavior in that fast thermal back relaxation in rod shape (monoazo substitution) form, while long thermal back relaxation in bent shape forms (diazo substitution). Both relaxation times are useful for creation of optical rewritable boards, optical storage devices, etc. [ABSTRACT FROM AUTHOR]

ABSTRACT This work analyses the SRG forming ability of a linear and a crosslinked polymer, both based on the same azo chromophore (Disperse Red 19, DR19) and diisocyanate (4,4'-metilen- bis(cyclohexyl isocyanate), DI) with similar glass transition temperature values. The effect of the experimental and geometrical parameters (such as beams polarization direction and interference pattern spacing) on the surface modulation process was examined as well. The absence of photodegradation or bleaching was corroborated by comparing Raman spectra inside and outside the SRG zone. Being a very important subject matter, the influence of crosslinking on the inscription rates and thermal stability of SRGs was investigated. Crosslinked films with an interesting modulation and good grating stability, even at high temperatures (160 °C), were obtained. Gratings shape was retained, and significant diffraction was still observed even well above the Tg of the bulk sample. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 587-594 [ABSTRACT FROM AUTHOR]

ABSTRACT Vesicles with hydrophobic shells have been self-assembled through three kinds of amphiphilic block copolymers containing pendent azopyridine groups with different spacers, namely PNIPAM -b-PAzPyn ( n = 0, 2, 6), respectively. By polarization laser-trapping Raman spectroscopy, the photoinduced orientation behaviors of azopyridine groups within the vesicle shells have been investigated and it is found that spacer lengths affect the orientation of the azopyridine groups and the morphologic structure of the vesicle shells. The exact experimental results show that the orientation is dynamic for the pendent azopyridine groups with connecting spacers of 2 or 6 methylene units rather than those without spacers, so the vesicles of PNIPAM -b-PAzPy6 can be changed to show a typical 'soft' character compared with its solid films when irradiated with a relatively weak polarized UV light of 190 µW/cm2. However, the vesicles of PNIPAM -b-PAzPy0 without spacers do not change even though the azopyridine units can be oriented. By quantitative Raman spectral analysis, it is found that the isomerization degree of azopyridine units is 70% for PNIPAM -b-PAzPy6 yet it is 10% for PNIPAM -b-PAzPy0, which shows a close relationship between aggregation and isomerization of azopyridine units under a weak UV light. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 415-421 [ABSTRACT FROM AUTHOR]

A series of epoxy-based azo polymers was synthesized from a precursor polymer that was obtained by step-polymerization between 1,4-cyclohexanedimethanol diglycidyl ether and aniline. The azo polymers were prepared by post-polymerization azo-coupling reactions of the precursor polymer with several diazonium salts to introduce azo chromophores bearing different electron-withdrawing groups. Photoinduced colloid deformation and surface modulation were investigated by using self-assembled colloidal spheres and spin-coated films of the azo polymers upon irradiation with Ar + laser. Rates of both colloid deformation and surface modulation showed a close correlation with the electron-withdrawing groups on the p -positions of the azobenzene moieties. The azo polymer bearing the carboxyl group as the electron-withdrawing substituent showed much faster rates for both the colloid deformation and surface modulation compared with the others in the series. For comparable cases, the photoinduced deformation rates were obviously faster for the newly synthesized polymer compared with an epoxy-based azo polymer reported before. [ABSTRACT FROM AUTHOR]

ABSTRACT Three main chain thermotropic liquid crystalline (LC) azobenzene polymers were synthesized using the azobenzene twin molecule (P4P) having the structure Phenylazobenzene-tetraethyleneglycol-Phenylazobenzene as the AA monomer and diols like diethylene glycol, tetraethylene glycol (TEG), and hexaethylene glycol as the BB comonomer. Terminal C(O)OMe units on P4P facilitated transesterification with diols to form polyesters. All polymers exhibited stable smectic mesophases. One of the polymers, Poly(P4PTEG) was chosen to prepare composite polymer electrolytes with LiCF3SO3 and ionic conductivity was measured by ac impedance spectroscopy. The polymer/0.3 Li salt complex exhibited a maximum ionic conductivity in the range of 10−5 S cm−1 at room temperature (25 °C), which increased to 10−4 S cm−1 above 65 °C. The temperature dependence of ionic conductivity was compared with the phase transitions occurring in the sample and it was observed that the glass transition had a higher influence on the ionic conductivity compared to the ordered LC phase. Reversible ionic conductivity switching was observed upon irradiation of the polymer/0.3 Li salt complex with alternate UV and visible irradiation. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 629-641 [ABSTRACT FROM AUTHOR]

ABSTRACT A new methacrylate containing a 2,6-diacylaminopyridine (DAP) group was synthesized and polymerized via RAFT polymerization to prepare homopolymethacrylates (PDAP) and diblock copolymers combined with a poly(methyl methacrylate) block (PMMA- b-PDAP). These polymers can be easily complexed with azobenzene chromophores having thymine (tAZO) or carboxylic groups with a dendritic structure (dAZO), which can form either three or two hydrogen bonds with the DAP groups, respectively. The supramolecular polymers were characterized by spectroscopic techniques, optical microscopy, TGA, and DSC. The supramolecular polymers and block copolymers with dAZO exhibited mesomorphic properties meanwhile with tAZO are amorphous materials. The response of the supramolecular polymers to irradiation with linearly polarized light was also investigated founding that stable optical anisotropy can be photoinduced in all the materials although higher values of birefringence and dichroism were obtained in polymers containing the dendrimeric chromophore dAZO. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 3173-3184 [ABSTRACT FROM AUTHOR]

The chiral atropisomeric monomer R-(+)-2-amino-1,1'-binaphthalen-2-ol provides convenient access to a number of azobenzene modified poly(ester-amide)s having highly-ordered main-chain arrangements of their constituent monomer groups. When evaluated in dilute solution environments, each of the polymers that contain the azobenzene stimuliphore undergo photo-induced oscillations in optical rotatory power when stimulated by multiple UV light-visible light illumination cycles. Polymer behavior is strongly influenced by the particular sequence of monomer units positioned along the chiral ester-amide backbone. Periodic variants that are fashioned from R-binaphthylene, azobenzene and para-phenylene segments exhibit particularly interesting response profiles. In certain cases, their light-modulated chiroptical outputs alternate between two discrete states, fluctuating between positive and negative specific rotations, or reversibly interconverting between optically active and optically inactive endpoints. This chiroptical switching behavior is greatly influenced by the choice of solvent, providing an added means for tuning the binary outputs afforded by these structurally well-defined materials. [ABSTRACT FROM AUTHOR]

ABSTRACT Triple stimuli (temperature/pH/photo)-responsive amphiphilic glycopolymer, poly(2-(dimethylamino)ethyl methacrylate- co-6- O-methacryloyl-1,2,3,4-di- O-isopropylidene-D-galactopyranose)- b-poly(4-(4-methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA- co-MAIpGP)- b-PMAZO] was synthesized by atom transfer radical polymerization, followed by the hydrolysis of MAIpGP groups, resulting in the target product poly(2-(dimethylamino)ethyl methacrylate- co-6- O-methacryloyl-D-galactopyranose)- b-poly(4-(4-methoxyphenylazo)phenoxy methacrylate) [P(DMAEMA- co-MAGP)- b-PMAZO]. The composition, moleculer weight, and moleculer weight distribution of the resultant polymers were characterized by 1H NMR and gel permeation chromatography. The micelles formed in aqueous solutions were simulated by various chemical and physical stimuli and characterized by dynamic light scattering, transmission electron microscopy, and UV-vis spectroscopy. It was found that the glycopolymer is responsive to three different types of stimulus (light, temperature, and pH). The poly(2-(dimethylamino) ethyl methacrylate) segments give thermo- and pH-responsiveness. The presence of the azobenzene moiety endows the block copolymer to exhibit light-responsiveness due to its reversible trans-cis isomerization conversion. The triple stimuli-responsive glycopolymer micelles can simulate biomacromolecues in vivo/ in vitro environment and can be expected to open up new applications in various fields. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2131-2138 [ABSTRACT FROM AUTHOR]

ABSTRACT A facile, general, and highly efficient one-pot approach to obtain azobenzene (azo)-containing molecularly imprinted polymer (MIP) nanoparticles with photoresponsive template binding and release properties in aqueous media is described, which involves the combined use of hydrophilic macromolecular chain transfer agent-mediated reversible addition-fragmentation chain transfer precipitation polymerization and easily available water-insoluble azo functional monomers. The resulting azo-containing MIPs were characterized with dynamic laser scattering (DLS), SEM, FTIR, static contact angle and water dispersion studies, and equilibrium binding experiments. They have proven to be nanoparticles (their diameters being around 104-397 nm, as determined by DLS in methanol) with surface-grafted hydrophilic polymer brushes and exhibit excellent pure water-compatible template binding properties. Moreover, obvious photoregulated template binding behaviors were observed for such azo-containing MIP nanoparticles, which led to their largely accelerated template release in the aqueous media under the UV light irradiation. Furthermore, the general applicability of the strategy was also demonstrated. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 1941-1952 [ABSTRACT FROM AUTHOR]

The recording of polarization gratings in films of a cholesteric liquid crystalline polymer with different helix pitch was studied in detail. For this purpose, the cholesteric mixture of the nematic azobenzene-containing copolymer with a chiral-photochromic dopant was prepared. The utilization of such mixture has made possible to realize dual optical photorecording in one system, first due to the phototuning of the helix pitch by UV light and second the polarization grating recording process by exposure with polarized visible light. The diffraction efficiency strongly depends on the cholesteric helix pitch and films thickness: the increase of the confinement ratio d/ p (where d, film thickness; p, helix pitch) results in growth of the diffraction efficiency. Comparison of the induction of polarization gratings in cholesteric, nematic (copolymer without chiral dopant), and amorphous (nonannealed) cholesteric films revealed that only the cholesteric films were characterized by significant oscillations in the diffraction efficiency signal as well as by the presence of the maximum in the first-order diffraction efficiency in the initial stage of the grating recording process. It was found that in addition to the polarization grating surface relief gratings (SRGs) were also formed in the studied systems, however, the amplitude of the SRG inscribed in the cholesteric films was lower (∼20 nm) compared to the grating amplitude obtained in nematic films (∼60 nm). Moreover, increasing helix pitch resulted in a decrease of the SRG amplitude. The obtained experimental data demonstrate the great potential of cholesteric LC mixtures of such type for different applications as photoactive materials for photonics. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 773-781 [ABSTRACT FROM AUTHOR]

ABSTRACT The photomechanical response and photochemistry of a conventional, unsubstituted azobenzene-functionalized liquid crystalline polymer network (azo-LCN) is contrasted to that of an analogous material prepared with meta-fluorinated azobenzene chromophores. The polydomain azo-LCN materials exhibit nearly identical thermomechanical and optical properties. Photomechanical characterization indicates that the fluorination of the azobenzene chromophore reduces the deflection of cantilevers composed of the materials by 50%, which spectroscopic analysis reveals is due to a reduction in the ability of this material to isomerize and potentially reorient. This work is further confirmation that the underlying photochemistry of azobenzene is a primary contributor to the generation of photomechanical work in these materials. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 876-882 [ABSTRACT FROM AUTHOR]

Abstract: In this paper, photoresponsive behavior of multi-bilayered films having precisely controlled layer thickness prepared by stacking an azo-functionalized polymer liquid crystal, PMAzXAc, and polyvinyl alcohol alternatively, PVA, is described. The multi-bilayered films were found to reflect a light of specific wavelength depending on the layer thickness and refractive index, and showed the reversible change in the reflection intensity by irradiation with visible and UV lights. The change in the reflection intensity was brought about by change in the molecular orientation of PMAzXAc between an out-of-plane orientation and a photo-induced isotropic state, and was strongly dependent on the number of methylene spacer of PMAzXAc linking the azobenzene side group with the acrylate polymer main chain. PMAz6Ac with hexa-methylene spacer showed the largest change in the reflection intensity, while smaller change in the reflection intensity was observed for PMAzXAc having shorter or longer methylene spacer than 6. The effect of the methylene spacers on the photochemical change in the molecular orientation of azobenzene chromophores in the multi-bilayered films will be discussed. [Copyright &y& Elsevier]

In this paper, novel polymers with azobenzene moiety with alkyl spacer and different substituents units are presented. Azopolymers were obtained by a two-step synthetic approach. This includes the preparation of a methacrylic monomers and their polymerization. Their photophysical and photochemical properties have been investigated. Polymers were characterized and evaluated by1HNMR, IR, UV spectroscopy. Thermal stability was characterized by DSC method. The synthesized polymers exhibited glass transition temperatures in the range of 110–140°C. [ABSTRACT FROM PUBLISHER]

ABSTRACT Azopolymers comprise a unique materials platform, in which the photoisomerization reaction of azobenzene molecules can induce substantial material motions at molecular, mesoscopic, and even macroscopic length scales. In particular, amorphous azopolymer films can form stable surface relief patterns upon exposure to interfering light. This allows obtaining large-area periodic micro- and nanostructures in a remarkably simple way. Herein, recent progress in the development of azopolymer-based surface-patterning techniques for photonic applications is reviewed. Starting with a thin azopolymer layer, one can create a variety of photonic elements, such as diffraction gratings, microlens arrays, plasmonic sensors, antireflection coatings, and nanostructured light-polarization converters, either by using the azopolymer surface patterns themselves as optical elements or by utilizing them to microstructure or nanostructure other materials. Both of these domains are covered, with the aim of triggering further research in this fascinating field of science and technology that is far from being harnessed. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 163-182 [ABSTRACT FROM AUTHOR]

Highlights: [•] Cellulose ethers bearing azobenzene groups were prepared by homogeneous etherification. [•] Azobenzene celluloses with DSazo ≥0.53 showed good solubility in aprotic solvents. [•] Azobenzene celluloses showed reversible trans-cis transition under light irradiation. [ABSTRACT FROM AUTHOR]

ABSTRACT A new approach to the synthesis of photoactive comb-shaped homo- and copolyamides containing azobenzene, cinnamate, and coumarin side groups for photoalignment of liquid crystals was elaborated. Photooptical properties and photoorientational ability of these polymers with respect to liquid crystals were studied. It was shown that polarized UV irradiation of all spin-coated polyamides leads to orientation of liquid crystalline molecules deposited on the polyamide thin films. The synthesized polymers containing cinnamate and coumarin side groups as well as azobenzene-containing cyano- and nitro-substituted polymers demonstrated good orientation ability in relation to liquid crystals displaying photoinduced planar orientation with high dichroism values within the range of 0.68-0.72. Contrary to the above-mentioned polyamides, azobenzene-containing fluorosubstituted polymers induced a homeotropic orientation of liquid crystals. It was shown that the synthesized photoactive polyamides can be considered as promising photoalignment materials for application in display technology, photonics, and other 'smart' optical devices. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4031-4041 [ABSTRACT FROM AUTHOR]

ABSTRACT Azobenzene-containing polymers offer tremendous advantages and opportunities over other stimuli-responsive materials to interface with biology. Azobenzene's fast, reversible, and innocuous cis- trans geometrical isomerization can be leveraged into dramatic intra- and inter-molecular changes when incorporated in polymeric materials. Azobenzene use has grown from a colorant, through to optical storage materials, and most recently in a variety of biologically themed applications. This review highlights the broad impact this photo-switch has had in recent years and offers a snapshot of the research landscape at the interface between photochemistry and biology. From photo-reversible micelles and peptides to controlled drug release and sensing, the versatility of azobenzene makes it a favored photo-switch found in many emerging applications. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3058-3070 [ABSTRACT FROM AUTHOR]

Azo polymers-coated AuNPs (poly(DMA-co-PAPA)-coated AuNPs and poly(NIPAM-co-PAPA)-coated AuNPs) are prepared by the free radical “grafting through” copolymerization of MAEL-capped AuNPs, PAPA and DMA or NIPAM in THF solution using AIBN as initiator. The characterization of azo polymers-coated AuNPs is performed by UV-Vis, TEM, XPS, TGA, FT-IR and1H-NMR spectroscopy. The influence of α-CD and α-CD derivatives (per-6-PDMA-α-CD and per-6-PNIPAM-α-CD) on the thermosensitivity of azo polymers-coated AuNPs aqueous solution is investigated. It is found that azo polymers-coated AuNPs aqueous solution barely exhibits any temperature sensitive properties. After the addition of α-CD or per-6-PDMA-α-CD, the thermosensitivity of azo polymers-coated AuNPs has been slightly enhanced due to the formation of inclusion complexes by molecular recognition of α-CD and azobenzene moiety. However, azo polymers-coated AuNPs exhibit excellent thermosensitivity with a narrow window of phase transition when the inclusion complexes are formed by molecular recognition between azo polymers-coated AuNPs and per-6-PNIPAM-α-CD after the addition of per-6-PNIPAM-α-CD. The lower critical solution temperature (LCST) is 29.8°C and 30.8°C for poly(DMA-co-PAPA)-coated AuNPs inclusion complexes of 2.5 g·L−1and 1.25 g·L−1, respectively. For the poly(NIPAM-co-PAPA)-coated AuNPs system, the LCST is measured to be 25.4°C and 27.3°C corresponding to 2 g·L−1and 1 g·L−1inclusion complexes aqueous solution. These results indicate that the thermosensitivity of azo polymers-coated AuNPs can be controlled by molecular recognition between the azobenzene group in AuNPs and α-CD moiety. [ABSTRACT FROM AUTHOR]

We have demonstrated the preparation of a series of photoaddressable supramolecular block copolymers by mixing a carboxy-terminated azobenzene derivative, 6-[4-(4′-cyanophenylazo)phenyloxy]hexanoic acid (AZO), and two polystyrene- b-poly(4-vinylpiridine) (PS- b-P4VP) block copolymers. AZO can be selectively attached to the P4VP block of PS- b-P4VP through hydrogen bonding interactions. The assembly of AZO with vinylpyridine group-containing polymers was initially investigated on a model system composed of P4VP homopolymer and AZO. Homogeneous liquid crystalline materials were obtained for ratios of AZO to vinylpyridine repeating unit, x, lower or equal to 0.50. Mixtures with higher x resulted in heterogeneous materials showing clear macrophase separation. Accordingly, a series of hydrogen-bonded complexes of PS- b-P4VP and AZO, PS- b-P4VP(AZO) x, with x = 0.25 and x = 0.50 were prepared. Lamellar and spherical morphologies were observed for the complexes based on PS24- b-P4VP9.5 ( Mn,PS = 24,000, Mn,P4VP = 9500) and PS24- b-P4VP1.9 ( Mn,PS = 24,000, Mn,P4VP = 1900), respectively. Photoinduced orientation of the azobenzene units was obtained in films of P4VP(AZO) x and PS- b-P4VP(AZO) x with x = 0.25 and 0.50 by using 488 nm linearly polarized light and characterized through birefringence and dichroism measurements. This investigation shows a versatile and less laborious approach to azobenzene-containing polymer materials with low chromophore content, of interest in optical application. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

A polymer network is prepared by the thiol-yne photopolymerization of multifunctional dendrimer with a tetrathiol crosslinker. The network obtained shows a liquid crystalline phase at room temperature, which has been characterized by optical microscopy, differential scanning calorimetry, and X-ray diffraction. Photoinduced deformation of uniaxially aligned free-standing films of the photocrosslinked material has been demonstrated. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of organic nanoparticles composed of a polymer network of azobenzene moieties and capable of reproducible, photoinduced mechanical actuation are reported. The molecules within the nanoparticles undergo co-ordinated, reversible isomerization between cis- and trans-conformations in response to ultraviolet and visible electromagnetic radiation, resulting in a reversible 20% height contraction of nanoparticles adsorbed on a substrate. The kinetics of the actuation response as a function of light intensity and duration are reported and closely match the molecular kinetics of azobenzene photoisomerization. The results support the proposed mechanism of co-ordinated molecular conformational changes resulting in observable nanoscale actuation. [ABSTRACT FROM AUTHOR]