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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]

Well-defined azobenzene-containing side-chain liquid crystalline diblock copolymers composed of poly[6-(4-methoxy-azobenzene-4′-oxy) hexyl methacrylate] (PMMAZO) and poly(γ-benzyl- L-glutamate) (PBLG) were synthesized by click reaction from alkyne- and azide-functionalized homopolymers. The alkyne-terminated PMMAZO homopolymers were synthesized by copper-mediated atom transfer radical polymerization with a bromine-containing alkyne bifunctional initiator, and the azido-terminated PBLG homopolymers were synthesized by ring-opening polymerization of γ-benzyl- L-glutamate- N-carboxyanhydride in DMF at room temperature using an amine-containing azide initiator. The thermotropic phase behavior of PMMAZO- b-PBLG diblock copolymers in bulk were investigated using differential scanning calorimetry and polarized light microscopy. The PMMAZO- b-PBLG diblock copolymers exhibited a smectic phase and a nematic phase when the weight fraction of PMMAZO block was more than 50%. Photoisomerization behavior of PMMAZO- b-PBLG diblock copolymers and the corresponding PMMAZO homopolymers in solid film and in solution were investigated using UV-vis. In solution, trans-cis isomerization of diblock copolymers was slower than that of the corresponding PMMAZO homopolymers. These results may provide guidelines for the design of effective photoresponsive anisotropic materials. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

New class of photo and electrically switchable azobenzene containing pendant bent-core liquid crystalline monomers ( AZBM 1, 2, and 3) and their polymers ( AZBP 1, 2, and 3) are reported. The synthesized precursors, monomers, and polymers were characterized by FT-IR, 1H, and 13C NMR spectroscopy. Thermal stability of polymers was examined by thermogravimetric analysis and revealed stable up to 260 °C. The mesophase transition of monomers and polymers are observed through polarized optical microscopy (POM) and further confirmed by differential scanning calorimetry (DSC). The electrically switching property of monomers and their polymers were studied by electro-optical method. Among the three monomers AZBM 1, 2, and 3, AZBM 1 and 2 exhibit antiferroelectric (AF) switching and AZBM 3 exhibits ferroelectric (F) switching behavior. On the other hand, low molecular weight polymers ( AZMP 1, 2, and 3) show weak AF and F switching behavior. The photo-switching properties of bent-core azo polymers are investigated using UV-vis spectroscopy, trans to cis isomerization occurs around 25 s for AZBP-1 and 30 s for AZBP-2 and 3 in chloroform, whereas reverse processes take place around 80 and 90 s. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013 [ABSTRACT FROM AUTHOR]

Abstract: Amphiphilic polymers are well known for their characteristics to form various self-assembling structures under proper conditions. Amphiphilic azo polymers, which are amphiphilic polymers functionalized with aromatic azo moieties, can combine wealthy photoresponsive properties with the self-assembling feature. In recent years, a wide variety of amphiphilic azo polymers have been developed through different molecular design strategies and synthetic routes. This article reviews the background, recent development, current approaches, and outlook of this rapidly developing research area. The emphasis is placed on the synthesis, self-assembly, and photoresponsive properties of amphiphilic azo polymers. According to the molecular architecture, the amphiphilic azo polymers are classified as homopolymers, random copolymers, block copolymers, star-like and dendritic polymers. The polymers show strong tendency to form well-organized structures at surfaces or interfaces, in solutions or dispersion mediums, and through phase-separation in solid thin-films. Colloidal arrays and porous thin films of amphiphilic azo polymers can be obtained through the vertical deposition method and solvent-induced structure inversion. The amphiphilic azo polymers and their self-assembled structures exhibit a variety of photoresponsive properties triggered by the trans–cis photoisomerization of azo chromophores. Some interesting variations caused by the light irradiation, such as the surface wettability change, surface-relief-grating formation, domain orientation, colloid deformation, micelle dissociation, vesicle bursting and fusion, are described in this review in detail. Such properties are promising for applications in areas such as optical devices, sensors, and drug delivery. [Copyright &y& Elsevier]

Three types of bi-functionalized copolymers ( P1FAz, P2FAz, and P3FAz) with different numbers of fluorene units and an azobenzene unit were synthesized and characterized using UV-vis and polarized absorption spectroanalysis. The trans-cis photoisomerization was conformed under 400 nm light irradiation for all copolymers in chloroform. However, in the film state, only the trans- cis photoisomerization occurred by mono-fluorene attached copolymer poly[(9,9-di- n-octylfluorenyl-2,7-diyl)- alt-4,4′-azobenzene)] ( P1FAz). Photo-induced alignment was achieved using the P1FAz film after irradiation with linear polarized 400 nm light and subsequent annealing at 60 °C. Surface orientation of a spin-coating film of poly(9,9-didodecylfluorene) ( F12) was achieved using the photo-induced alignment layer of the P1FAz film after annealing at 90 °C. The photo-induced alignment layer of P1FAz has potential application to the surface orientation technique for appropriate polymers, which will be useful for the fabrication of optoelectronics devices. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Novel azobenzene-containing block copolymers (BCs) with a polyester block bearing azobenzene moieties in the side chain and a poly (methyl methacrylate) (PMMA) block have been synthesized by the combination of atom transfer radical polymerization (ATRP), polycondensation, and 'click' chemistry. Two azide-terminated polyesters with different molecular weight (obtained by polycondensation) were coupled to an alkyne-functionalized PMMA (obtained by ATRP). Blends of the BC with the highest azo content (wt%) and an azopolyester homopolymer were also prepared. All these compounds were investigated by polarized light optical microscopy (POM), differential scanning calorimetry (DSC), and transmission electron microscopy (TEM). Polarized light-induced anisotropy was studied by birefringence and dichroism measurements. [ABSTRACT FROM AUTHOR]

The synthesis and polymerizability of imine CN monomers is surveyed. The investigated imines were either far more reactive than similarly substituted CC or CO monomers, or too stable to polymerize. Imines with electron-attracting substituents on N favor polymerization by anionic mechanism, but led only to low molecular weight polymers. Imines with a donor substituent on N, such as N-arylmethyleneimines, polymerized by cationic or anionic mechanism. 1- and 2-Aza-1,3-butadienes were also rather unstable and polymerized to oligomers. The symmetrically substituted 2,3-diaza-1,3-butadienes could be purified and polymerized successfully using anionic initiators, resulting in both 1,4- and 1,2-structures in the polymer backbone, depending on the substituents. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

We report systematic studies on a homologous series of twin liquid crystalline (LC) molecules based on phenyl and naphthyl azobenzene ( PnP and NpnNp) as well as segmented copolyesters based on them. The twin series had the structure azobenzene-oligooxyethylene-azobenzene, where the ethyleneoxy length was varied from 2 to 6 units. The LC properties of the twin series depended on the chemical structure of the azochromophore and also the length of the central oligooxyethylene segment. The PnP series exhibited smectic LC properties for n > three oligooxyethylene units. Conversely, NpnNp series exhibited spherulitic phases only for the shortest member - Np2Np. One non-LC short spacer twin ( P2P) and one LC long spacer twin ( P6P) were incorporated as part of a main chain polyester composed of fully aliphatic segments of sebacate and di or tetraethylene glycol (DEG/TEG) units by melt polycondensation. Non-LC P2P formed LC polymers even at low (5 mol %) incorporation in DEG-based copolymers, whereas the LC- P6P could do so only at 30 mol % incorporation. The LC properties of the twin molecules as well as copolymers were studied using differential scanning calorimetry, polarized light microscopy (PLM) along with variable temperature wide angle X-ray diffraction. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Light can wirelessly direct functional responses in photoresponsive polymeric materials and composites. The intensity, phase, and polarization of light can be spatially modulated into complex patterns with holography (intensity or polarization) or masking (intensity or phase). Deriving from these foundational properties of light, photoresponsive macromolecular systems exhibit exceeding potential to yield rapid and highly engineered macroscopic as well as spatially selectable mechanically adaptive responses useful as soft actuators or topographical surfaces in aerospace, automotive, and biomedical applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012 [ABSTRACT FROM AUTHOR]

Three new types of hyperbranched photoactive liquid crystalline siloxane polymers containing azo moieties were synthesized using click chemistry methodology. The polymers were soluble in most of the polar solvents like chloroform, tetrahydrofuran, dimethylformamide, dimethyl sulphoxide and dichloromethane. The molecular weights of the polymers were in the range of 9000-12,000 g mol−1. The trans-cis photoisomerization of the polymer were studied both under UV radiation and dark. The isomerization rate constants were found to be in the range of 0.7-1.4 × 10−2 sec−1 and 7.0 × −2.5 × 10−5 sec−1. The thermotropic behavior of the polymers was studied by using polarizing optical microscopy and differential scanning calorimetry, respectively. The polymers P1 and P2 showed liquid crystalline texture characteristic of nematic phase. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

End-capped and intramolecular azofunctional oligocaprolactones were characterized at molecular level by liquid chromatography electrospray ionization mass spectrometry (ESI MS) and NMR spectroscopy. The Disperse Red 19 (DR19) azofunctional oligomers, DC, were synthesized by ring-opening oligomerization of ε-caprolactone (ε-CL) initiated by the hydroxyl groups of DR19 azo dye. The reaction products consist of a minor fraction of end-capped azo functional oligocaprolactone (α-DC), that is, a single CL arm oligomer, and a major fraction of intramolecular azo functional oligocaprolactone (β-DC), that is, a two CL arms oligomer. The chromatographic separation was used to discriminate between α-DC and β-DC, and the results were confirmed by MS/MS performed on an ESI ion trap instrument. The results supported by accurate mass data obtained for product ions using an ESI quadrupole time of flight instrument demonstrate the qualitative discrimination at the molecular level between intramolecular and end-capped azofunctional oligoesters isomers through a relatively simple multistage mass spectrometry experiment. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012 [ABSTRACT FROM AUTHOR]

Three epoxy-based azo polymers (PEP-AZ-Cl, PEP-AZ-CN and PEP-AZ-NT) with high chromophore density were synthesized by using post-polymerization azo-coupling reactions between epoxy-based precursor polymer (PEP-AN) and diazonium salts of 4-chloroaniline, 4-aminobenzonitrile and 4-nitroaniline, respectively. The structures and properties of the azo polymers were characterized by using H-NMR, FT-IR, UV-Vis and thermal analyses. The photoinduced birefringence of the azo polymers was studied by irradiating spin-coated films of the polymers with laser beam at three different wavelengths (488, 532, and 589 nm). The results indicate that the photoinduced birefringence of the azo polymers is related with the electron-withdrawing group on azo chromophores and the excitation wavelength. The excitation wavelength that can cause the efficient responses is determined by the absorption band positions of the azo chromophores, which are mainly affected by the electron-withdrawing group on the chromophores. Therefore, the azo polymers containing chromophores with different electron-withdrawing groups show different responsive behavior to the irradiation light at different wavelengths. When irradiated with 488 nm light, PEP-AZ-Cl shows the shortest time to reach the saturated birefringence but with the lowest saturation birefringence level compared with the other two azo polymers. When irradiated with 532 nm light, PEP-AZ-CN shows the shortest time to reach the saturated birefringence. When irradiated with 532 and 589 nm light, PEP-AZ-NT shows the highest saturation birefringence level. [ABSTRACT FROM AUTHOR]

Abstract: Microstructure in two diblock methacrylic azo polymers and in some of their blends with PMMA of different molecular weights as well as their photoinduced anisotropy have been investigated. The block copolymers have similar structure but different azo content and degree of polymerization. A synthetic strategy based on a controlled radical polymerization (ATRP) of polymeric blocks and their coupling by click chemistry has been applied to obtain an azo block copolymer of high molecular weight. Microphase segregation has been observed in the block copolymers and in most of the blends. In blends of the block copolymer with lower degree of polymerization (Block 1) azo microdomains change from lamellar to spherical morphology when the azo content decreases from 24 to 3wt.%. In the block copolymer with higher degree of polymerization (Block 2) and its blends, down to 3wt.% azo content, spherical azo microdomains have been found. A decrease of the order parameter (η) and the photoinduced birefringence normalized to the azo content (|Δn|norm) has been found in blends of Block 1 when the azo content decreases. However, |Δn|norm and η values similar to those in the azo homopolymer have been observed in Block 2 and its blends. These blends can be used to lower the azo content while keeping a photoinduced response similar to that in the azo homopolymer. [Copyright &y& Elsevier]

Abstract: For the purpose of colonic drug targeting, poly(ester) and poly(amide) azopolymers were synthesized and characterized. The polymers were based on azobenzene--dicarboxylic acid. It was polycondensated either with specific diamines to yield polyamides or with specific diols to yield polyesters. The polymers were characterized by infrared spectroscopy, elemental analyses, 1H NMR and Thermogravimetric analysis (TGA). The molecular weights were measured by Gel Permeation Chromatography (GPC). The synthesized polymers showed a good film forming. Degradation of poly azobenzene diacid-co-ethlene glycol 4000 and polyazo benzene diacid-co-jeffamine 4000 as azopolymer by microorganisms was investigated and the results demonstrated that Aspergillus fungi have produced almost the highest value, however, Ganoderma resencium and Pleurotus ostreatus came in the last rank. The highest poly azobenzene diacid-co-jeffamine 4000 degradation rate constant (μmol/ml/h) was performed by Aspergillus fumigatus which produced 5.73±0.23μmol/ml/h at 228nm; whereas Aspergillus ochraceous produced the lowest poly azobenzene diacid-co-jeffamine 4000 degradation rate constant of 0.94±0.72μmol/ml/h at 332nm. [Copyright &y& Elsevier]

A series of methacrylic monomers containing azobenzene moiety with alkyl spacer and different substituents is synthesized. Their photophysical and photochemical properties have been investigated. The photophysical properties of these compounds are investigated by 1H NMR, IR, and UV spectroscopies. [ABSTRACT FROM AUTHOR]

A new interesting class of polyamides of diarylidenecycloalkanone containing azo groups in the polymer backbone 6a-d was synthesized by a solution polycondensation reaction of bis 2-aminoarylidene monomers 3a,b with 4,4'-azodibenzoyl dichlorides and 3,3'-azodibenzoyl dichlorides in NMP as a solvent, using anhydrous LiCl as a catalyst at room temperature. The model compounds 4, 5 were synthesized by the interaction of one mole of bis 2-aminoarylidene monomers 3a,b with two moles of benzoyl chloride using anhydrous LiCl as a catalyst in NMP at room temperature. The resulting polymers were characterized by elemental and spectral analyses, besides solubility and viscometry measurements. The thermal properties of those polymers were evaluated by TGA, DTG and DTA measurements and correlated to their structural units. X-ray analysis of the polymers showed that polyamides based on para-azo linkage have a higher degree of crystallinity than those based on meta-azo linkage in the region 2θ = 5-60°. In addition, the morphological properties of selected examples were tested by SEM. [ABSTRACT FROM AUTHOR]

In the large family of polymers, the azobenzene derivatives represent one fascinating materials class, along with stylbene and azomethinic derivatives. This interest is explained by combination of the properties of anisotropy with the photoinduced behaviors. The photoinduced birefringence, relief grating, the high optical nonlinearity resulted from the sin-anti isomerism, molecular reorientation, the exceptional stability to writing and erasing by laser radiation, are just the most important arguments for their usage of these polymeric architectures in the NLO field as: LCD, chemical sensing, devices for storage and transmission of information. This presentation covers the development and characterization a new series of materials from viewpoint of the modification of the polymer materials by the chemical transformation of the “common” polymer support an underlining: solvatochromic and photorefractivity properties. [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 °C under nitrogen atmosphere. The release of 5-ASA under physiological conditions (pH = 7.8 and pH = 1.5) was investigated at body temperature (37 °C). The release rate of 5-ASA increased with increasing pH (i.e., 7.8 > 1.5). [ABSTRACT FROM AUTHOR]

Abstract: A series of hydroxy and carboxy group containing azobenzene compounds were synthesized and investigated by UV–vis and fluorescence spectroscopy. It could be shown that the ambient medium exerted a strong influence on the absorption behavior and the trans–cis isomerization behavior of the azo compounds. Especially in the case of hydroxy group functionalized azobenzenes, deprotonation with NaOH or a polymeric base changed the spectral behavior of the compounds remarkably. A strong bathochromic shift of the dyes’ longest wavelength absorption band was observed. Furthermore, the influence of different solvents and different polymeric matrices on the trans–cis isomerization behavior of the azobenzenes was investigated. The results are discussed in terms of utilization of the azo dyes as probe molecules for interactions in polymer blends. [Copyright &y& Elsevier]

New azo polymers and a polymeric complex with cobalt based on them were created, and the effect of interaction of the chromophores on the electrooptical effect in films of these materials was investigated. It was established that with increase in the length of the “spacer” and with the possibility of the formation of hydrogen bonds between the substituents in the azobenzene groups the time of the changes in the optical characteristics of the films decreases and their magnitude increases under the influence of the electric field. A phenomenological model of the effect of aggregates of the azobenzene groups attached to the main polymer chain by the spacers on the electrooptical characteristics of the films is proposed. [ABSTRACT FROM AUTHOR]

Abstract: This paper reports detailed synthesis and characterization of some new high-T g photorefractive polymers, polyphosphazene P3–P8. They were obtained via a post-azo coupling reaction. The resulting materials have been characterized by means of 1H NMR, 31P NMR, FT-IR, UV–vis, GPC and DSC. Chromophore contents up to 14mol% have been realized. The polymers had high glass-transition temperatures and good optical transparency. Measurements reveal that they possess relatively large magnitude of photoinduced birefringence. [Copyright &y& Elsevier]

Two novel main-chain aromatic polyamides containing azobenzene were synthesized by polycondensation of trans-azobenzene-4,4′-dicarbonyl chloride with various aromatic diamines under low temperature. Their molecular structures were identified to be symmetric and regular by Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy and elemental analysis. Polymers exhibited not only high thermal stability, but also lyotropic liquid crystal (LC) phases in N,N-dimethylacetamide solution which is due to hydrogen bonding and an ordered rigid structure. The crystal behaviours of the polymers were studied with X-ray diffraction analysis, and the photochromism was investigated with an ultraviolet–visible spectrophotometer with 365 nm ultraviolet irradiation. An abnormal change of the crystal behavior and thermal stability of polymer was found to be related with molecular structure containing ether linkage. The azo polyaramides can be applied in fields of optical techniques and potential photochromics fibres spinning in wide temperature ranges [ABSTRACT FROM AUTHOR]

Abstract: The well-defined phenylazo indazole-terminated polystyrene (PS) was successfully prepared via reversible addition-fragmentation chain transfer (RAFT) polymerization of styrene (St) mediated by a novel chain transfer agent (CTA) bearing phenylazo indazole moieties in the Z group, benzyl-5-(4-(dimethylamino)phenylazo) indazole-1-carbodithioate (BPCD). The fluorescence emission of BPCD and the phenylazo indazole-terminated PS in chloroform (CHCl3) before and after the 365nm ultraviolet irradiation was investigated. Interestingly, the fluorescence intensities of BPCD and the phenylazo indazole-terminated PS in CHCl3 were both sensitive to the 365nm ultraviolet irradiation. The fluorescence intensities of these solutions increased with the irradiation time and reached maximum at 110min. The light-driven fluorescence enhancement of BPCD and the phenylazo indazole-terminated PS were both attributed to the formation of spherical aggregate originated from the trans–cis isomerization of azobenzene moieties in BPCD and PS chain, which was confirmed by transmission electron microscopy (TEM), 1H NMR, UV and dynamic light scattering (DLS) spectra. [Copyright &y& Elsevier]

Abstract: An azo prepolymer (TAZ) was synthesized by reaction between Disperse Orange 3 (DO3) and diglycidyl ether of bisphenol A (DGEBA). The resulting TAZ was blended with DGEBA and two different monoamines, one aliphatic and one aromatic, benzylamine (BA) and m-toluidine (MT), to prepare various azo copolymers with different azo contents. In addition, two guest–host systems were prepared: 5.16% by weight of DO3 in DGEBA-BA and in DGEBA-MT polymers. Their reversible optical storage properties were studied and compared. The maximum obtainable birefringence increases linearly with TAZ weight fraction, independently of the power of the writing beam, the environment in which the azo moiety is located, and the bonding between the dye and the matrix. It was found that, in BA-based copolymers, with lower T g, the fraction of birefringence conserved after relaxation is smaller and the writing rates are higher than in MT-based copolymers. The film thickness dependence of the birefringence signal is also analyzed. [Copyright &y& Elsevier]

Abstract: A series of soluble polyacrylates containing different azobenzene side chains have been synthesized via atom transfer radical polymerization (ATRP) technique, from which the side-chain nonlinear optical (NLO) polymers with controllable molecular weight and low polydispersity (1.1–1.4) have been obtained. The third-order NLO absorption and refraction coefficients were simultaneously determined by Z-scan technique. The polymerization activity of the azobenzene-containing acrylate monomers and the third-order NLO properties of the obtained polyacrylates were both dominated by the electronic effect of the different substituents in the azobenzene side chain. The results of Z-scan with and without an aperture showed that all the azobenzene-containing monomers and polymers have both nonlinear absorption and nonlinear refraction. The third-order NLO susceptibility (χ (3)) of all the azobenzene-containing samples under the laser irradiation is 1.0–5.0×10−11 esu. [Copyright &y& Elsevier]

Copolymer containing new thermally reversible click chemistry‐assisted triazole‐substituted azobenzene and fulgimide units in the pendant F‐co‐A was prepared by free‐radical solution addition polymerization technique. The F and A were also prepared for comparison. The DSC analysis of F indicates that the polymer possessing the C‐form of fulgimide unit exhibited higher Tm than that of E‐form of the same polymer and revealed that the C‐form of fulgimide unit in F is highly ordered. The cis‐trans back isomerization behavior of the click chemistry‐assisted triazole‐substituted azobenzene unit in film A has thermal irreversibility, while in F‐co‐A it exhibited thermal reversibility. The UV‐exposed film of F‐co‐A heated around Tg leads to cis‐trans back isomerization of azobenzene unit and thermally stable C‐form of fulgimide which retains its conjugated structure where both the photochromic units are converted into planar conformations and exhibit high fluorescence properties. The fluorescence maxima of C‐form in F‐co‐A red shifted compared with F, because the substituted triazole ring in the azobenzene unit stabilized the C‐form of fulgimide unit. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7843–7860, 2008 [ABSTRACT FROM AUTHOR]

Abstract: A novel amphotropic polymer which could exhibit liquid-crystalline behavior both in the solvent and in the heating process was synthesized through azo polymers grafting from cellulose nanocrystals (CNCs). The CNCs, prepared by acid hydrolysis of filter paper, were characterized by Atomic Force Microscopy (AFM). Poly{6-[4-(4-methoxyphenylazo)phenoxy] hexyl methacrylate}(PMMAZO), which was a liquid-crystalline polymers (LCP), was successfully to graft from CNC via Atom transfer radical polymerization (ATRP). The structure and thermal properties of the PMMAZO-grafted CNC were investigated using Fourier transform infrared spectroscopy (FT-IR) and thermogravimetric analyses (TGA). Its phase structures and transitions were studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM). The experimental results showed that the PMMAZO-grafted CNC exhibited both types of liquid crystal formation, thermotropic and lyotropic. [Copyright &y& Elsevier]

Three kinds of photoresponsive copolymers with azobenzene side chains were synthesized by radical polymerization of N-4-phenylazophenylacrylamide (PAPA) with N-isopropylacrylamide (NIPAM), N,N-diethylacrylamide (DEAM) or N,N-dimethylacrylamide (DMAM) respectively. Their structures were characterized by FT-IR, 1H-NMR and UV/Vis spectroscopy. Their reversible photoresponses were studied with or without α-cyclodextrin (α-CD), which showed that both the copolymers and their inclusion complexes with α-CD underwent rapid photoisomerization. The lower critical solution temperature (LCST) of the copolymers and their inclusion complexes with α-CD were investigated by cloud point measurement, which showed that the LCST of three kinds of copolymers increased largely after adding α-CD. After UV irradiation on the solutions of copolymers and their inclusion complexes, the LCST of the copolymers increased slightly with the absence of α-CD, while decreased largely with the presence of α-CD. Furthermore, the LCST reverted to its originality after visible light irradiation. This change of LCST could be reversibly controlled by UV and visible light irradiation alternately. In particular, in the copolymer of PAPA and DMAM, the reversible water solubility of the inclusion complexes could be triggered by alternating UV and visible light irradiation. [ABSTRACT FROM AUTHOR]

Abstract: A series of main chain azobenzene polymers containing diacetylene moieties with different lengths of the spacer {–[CCH2–O–C6H4–OCO–(CH2) m –O–C6H4–NC6H4–O–(CH2) m –OCO–C6H4–O–CH2–Clic> n –, where m =3, 6, 11} were synthesized by oxidative coupling polymerization. These polymers had molecular weights of 17,600–68,600 and polydispersity indices of 1.2–1.8 as determined by gel permeation chromatography using polystyrene as a standard. Their structures and properties were characterized and evaluated with NMR, FT-IR, X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC) and nonlinear optical (NLO) analyses. All the polymers could be cross-linked at the elevated temperatures due to the polymerization reactions of the diacetylene groups in the polymer backbone, and the cross-linked polymers showed dramatically modified properties, such as thermal stability and solvent resistance. The third-order nonlinear susceptibilities of the cross-linked polymers were evaluated by means of the Z-scan technique and calculated to be 3.60×10−9, 2.73×10−9, 2.28×10−9 esu, respectively, whereas the un-cross-linked polymers showed no obvious NLO property. [Copyright &y& Elsevier]

Abstract: The synthesis and characterization of some new high-T g photorefractive polymers, polyphosphazene P3–P8, were described. They were obtained via a post-azo coupling reaction. The resulting materials have been characterized by means of 1H NMR, 31P NMR, FT-IR, UV–vis, GPC and DSC. Chromophore contents up to 14mol% have been realized. The polymers had high glass transition temperatures and good optical transparency. Measurements reveal that they possess relatively large magnitude of photoinduced birefringence. [Copyright &y& Elsevier]

Abstract: Eight novel polyurethanes (PUs) based on 4,4′-[1,4-phenylenedi-diazene-2,1-diyl]bis(2-carboxyphenol) and 4,4′-[1,4-phenylenedi-diazene-2,1-diyl]bis(2-chloro- phenol) as hard segments with four diisocyanates viz., 4,4′-diphenyl-methane diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate were prepared. Structural and thermal characterization of the segmented PUs were determined by FT-IR, UV spectrophotometry, fluoroscence spectroscopy, 1H NMR, 13C NMR spectroscopy and DTA/TGA analysis. All the PUs contain domains of semi-crystalline and amorphous structures, as indicated by X-ray diffraction. PUs were soluble in polar aprotic solvents like N-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF) and dimethylsulfoxide (DMSO). [Copyright &y& Elsevier]

Abstract: The synthesis and characterization of a new high-T g photorefractive polymer, polyphosphazene P2, was described. It was obtained via a post-azo coupling reaction. The resulting material has been characterized by means of 1H NMR, 31P NMR, FT-IR, UV–vis, GPC and DSC. Chromophore contents up to 14mol% have been realized. The molecular weights of polyphosphazene P2 are 3.3×104 (M n) and 4.3×104 (M w), respectively; and the glass-transition temperature is high (170°C). Measurements reveal that it possesses relatively large magnitude of photoinduced birefringence (4.2–4.7×10−3). [Copyright &y& Elsevier]

Abstract: Conformationally restricted polyesters comprising alternating azobenzene and chiral binaphthylene main-chain units undergo photo-induced oscillations in optical rotatory power when stimulated with sequential intervals of ultraviolet and visible light exposure. The incorporation of flexible (oligo)ethylene oxide backbone segments into these constructs has resulted in a new family of materials having vastly altered photo-responsive chiroptical properties. Light-regulated outputs were found to be strongly dependent upon the length of the flexible backbone segments employed and on their specific locations of placement within the polyester chain. Most notably, the insertion of flexible oligo(ethylene oxide) spacer elements between neighboring binaphthylene and azobenzene main-chain units had a pronounced damping effect on the photo-dynamic behavior exhibited by these chiral systems. Similar results were noted for a related series of oligomeric model compounds that were specifically designed to mimic local monomer sequences present within the larger polyester structures. [Copyright &y& Elsevier]

In the last few years, some monomers such as phenols, anilines, pyridines, naphtols, Schiff bases and azo phenols have been subjected to oxidative polycondensation (OP) using NaOCl, H2 O2 and air O2 as the oxidants in aqueous alkaline or aqueous acidic medium. This resulted in oligomers with potential useful properties. The major reason behind these investigations was the economic and environmentally benign reaction process of OP. Therefore, this review diccusses OP and the obtained oligomers in detail. Additionally, chemical structures, physical properties, UV-Vis, FT-IR, 1H- and 13C-NMR analyses, thermal properties and coupling mechanism of all oligomers synthesized via OP are discussed and compared to those of polymers prepared by other oxidative methods. The probable potential applications of the obtained polymers and oligomers, such as antistatic and semi-conductivity, fluorescent, photoresist, opto-electronic, electrochromic, antimicrobial and photoresponsive properties, are also discussed in the last section. [ABSTRACT FROM AUTHOR]

Abstract: Series of epoxy-based polymers functionalized with methyl-substituted azobenzene chromophores have been designed and synthesized. The polymers synthesized were characterized by the spectroscopic methods and thermal analysis. Surface relief gratings (SRGs) were photofabricated on thin films of the azo polymers by exposure to an interference pattern of coherent Ar+ laser beams. The methyl substitution in the ortho-positions of the azo groups significantly influences the SRG inscription rates. The inscription rates decrease as the number of the methyl substituents increases. The rates are also related with the positions of the methyl substitution on the azo chromophores. The methyl substitution in the ortho-positions of the azo groups on anilino sides shows a more significant effect to decrease the inscription rates. Meanwhile, the type of the electron withdrawing groups in the para-positions of the azobenzene units also shows a significant effect on the SRG inscription rates. [Copyright &y& Elsevier]

Abstract: Azobenzene-substituted polythiophenes were prepared by copolymerization of 3-alkylthiophenes functionalized with an azo-chromophore and 3-alkylthiophenes as plastifying comonomers to improve solubility. Monomers with different oligomethylenic spacer and alkylic chain lengths were synthesized and copolymerized via FeCl3 oxidative polymerization. Polymer soluble fractions were characterized by 1H and 13C NMR, FTIR, UV–Vis spectroscopy, and GPC, DSC and TGA. Second-order non-linear optical properties were measured by the second harmonic generation technique. [Copyright &y& Elsevier]

Abstract: We have investigated a new optically active photochromic homopolymer poly[(R)-3-methacryloyloxy-1-(4′-cyano-4-azobenzene)pyrrolidine] containing in the side-chain a chiral group of one prevailing configuration linked to a trans-azoaromatic system. As expected it exhibits in solution homogeneous conformations with a prevailing chirality induced by dipole–dipole interactions between side-chain chromophores. Copolymers with the enantiomeric monomer (S)-3-methacryloyloxy-1-(4′-cyano-4-azobenzene)pyrrolidine have also been prepared in order to evaluate the effect on the photoinduced optical properties of side-chain chiral groups of opposite configuration in various ratios. The possibility of producing reversible photomodulation of linear birefringence without any significant degradation of these materials seems to be promising for their use in optical data storage. [Copyright &y& Elsevier]

Novel azobenzene functionalized hydroxypropyl methylcellulose (AZO-HPMC) polymers and their α-CD (α-Cyclodextrin) complexes have been prepared. FT-IR, 1H NMR and FT-Raman spectroscopy confirm the existence of azobenzene chromophores in AZO-HPMC polymers. α-CD can improve the water solubility of AZO-HPMC by formation of inclusion complexes with azobenzene side groups. Rheological studies substantiate that both AZO-HPMC and its α-CD complex undergo thermoreversible sol–gel transitions in aqueous solutions. Viscometric measurements suggest that the association between azobenzene side groups can be eliminated by α-CD. The effect of photoirradiation on the rheological behavior shows that the gelation temperature of AZO-HPMC increases after UV irradiation, while the gelation temperature of AZO-HPMC/α-CD complex decreases after UV irradiation. [Copyright &y& Elsevier]

The paper discusses the synthesis of new optically active azo diacids starting from two activated azo diesters (diethyl azodicarboxylate and ethyl phenylazocarboxylate) and various (l)-α-amino acids as: (l)-alanine, (l)-leucine, (l)-cysteic acid monohydrate and (l)-cystine. New chiral polymers derived from some of synthesized monomers were obtained under mild reaction conditions by unconventional polycondensation methods. The structure of synthesized compounds has been spectroscopically confirmed and the solubility, optical activity and thermal properties of the obtained materials are reported. To estimate the molecular weights of new polymers the 1H-NMR and viscometric data were used and obtained values were compared with those of the polymers with alike chain structure synthesized by similar procedures. [Copyright &y& Elsevier]

Two azo-containing polymers with pyrazoline group (polymers II and III) have been synthesized and their reversible optical storage properties tested in comparison with electron donor and acceptor substituted azobenzene-containing polymer I. The growth and relaxation process of birefringence signals were fit with biexponential functions. It was found that polymer II, in which azo chromophores are connected with the main chain through pyrazoline groups, has fast storage rate and good storage stability. The storage efficiency indicated that the introduction of pyrazoline groups in the polymers II and III has a positive effect. The birefringence per mole of azo chromophore showed that polymers II and III have four times the value of polymer I. The relative stability of the photoinduced birefringence decreased with the increase of temperature. [Copyright &y& Elsevier]

Epoxy-based azo polymers with three kinds of backbones, different types of azo chromophores, and selected degrees of functionalization (DFs), were synthesized through a post-polymerization azo-coupling scheme. The Tgs of the azo polymers were found to be considerably influenced by the substituents on the 4-positions of the azobenzene units and increased with the increase of the DFs of the polymers. Surface-relief-gratings (SRGs) were induced on the polymer films by interferenced Ar+ laser beams. With the same irradiating light intensity and approximately equal film thickness, the rates of SRG formation were found to be significantly dependent on the electron-withdrawing groups on the 4-positions of the azobenzene units. For the polymers with the same type of azo chromophores and backbone structure, the inscription rates increased with the increase of the DFs. Meanwhile, the backbone structure also exhibited some effect on the inscription rates through the ways such as changing chromophore loading density or main-chain rigidity. [Copyright &y& Elsevier]

Polarization holography is used to study the dynamics of optically induced gratings in azobenzene functionalized polymer films. The simultaneously formed birefringence grating (BG) and surface relief grating (SRG) are investigated by probing the grating formation process with orthogonal linearly polarized beams for different polarization combinations of the writing beams. Our experimental results indicate that for early writing times, vertically polarized beam diffract from the BG while the horizontally polarized beam gets diffracted predominantly from the SRG. Explanation based on the total electric field vector pattern due to interference of polarized beams and its effect on the material gives an insight into the physical processes responsible for the dual-grating formation. †Deceased [ABSTRACT FROM AUTHOR]

Azo polymers based upon 2-hydroxyethyl methacrylate, methyl methacrylate, and methacrylic acid, and containing N,N′-bis [(methacryloyloxyethyl)oxy(carbonylamino)]azobenzene as azo aromatic agent were evaluated in vivo as coatings for colon-specific drug delivery. The gastrointestinal absorption of theophylline from capsules coated with the azo polymers was examined in the proximal part of the small intestine and the cecum of male Wistar rats. The capsules were surgically inserted in the region of interest. The plasma concentration of the drug was higher when the capsules were inserted in the cecum as compared to the small intestine. The appearance of theophylline in the plasma when capsules were administered in the small intestine can be attributed to simple diffusion of the drug through the swollen polymer coating. Release and absorption from the cecum is the combined result of diffusion and degradation of the azo polymer coatings by bacterial azo reductase. [ABSTRACT FROM AUTHOR]

Copolymers of 2-hydroxyethyl methacrylate (HEMA) and methyl methacrylate (MMA), and terpolymers of HEMA, MMA, and methacrylic acid (MA) were synthesized in the presence of N,N′-bis(methacryloyloxyethyloxycarbonylamino)azobenzene (B(MOEOCA)AB) and evaluated as coating materials for colonic targeting. The release of ibuprofen, a model drug, from capsules coated with the azo polymers was investigated in vitro. The release medium was made up of sonicated rat cecal content, benzyl viologen, glucose-6-phosphate, glucose-6-phosphate dehydrogenase, and nicotine amide dinucleotide phosphate (NADP) in phosphate buffer (pH 6.8, 0.05M). The drug-release profiles indicate that the degradation of the azo polymer coatings depends on their degree of swelling, due to a higher accessibility of the azo bonds for the bacterial azo reductase. The best results were obtained with azo polymers containing MA: 98.7 (±1.1) % of ibuprofen was released after 19 hours residence in the release medium, while only 26.2 (± 4.9) % in the control experiment. These findings demonstrate that azo polymers are promising materials for delivering drugs selectivity to the colon. [ABSTRACT FROM AUTHOR]