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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., This work was supported by the MINECO, Spain, under the project MAT2011–27978-C02-01 and 202, Fondo Europeo de Desarrollo Regional (FEDER), Gobierno de Aragón and Fondo Social Europeo. Authors would also like to acknowledge the Advanced Microscopy Laboratory and Servicio de Microscopia Electrónica de Materiales of the Universidad de Zaragoza (Servicios de Apoyo a la Investigación, SAI). I. Díez acknowledges funding from CSIC and Fondo Social Europeo through a JAEDoc fellowship.

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.

Azopolymers comprise a unique materials platform, in which the photoisomerization reaction of azobenzene mole- cules can induce substantial material motions at molecular, mesoscopic, and even macroscopic length scales. In particular, amorphous azopolymer films can form stable surface relief pat- terns 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 diffrac- tion gratings, microlens arrays, plasmonic sensors, antireflec- tion 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 cov- ered, with the aim of triggering further research in this fasci- nating field of science and technology that is far from being harnessed. V C 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013, 00, 000-000

8 páginas, 9 figuras, 3 tablas., The molecular orientation in a side-chain liquid crystalline azopolymer with push–pull chromophores (Pol-PZ-CN) is studied by UV-vis spectroscopy, refractive index and second harmonic generation measurements. Fresh films show homeotropic arrangement, but irradiation with polarized light induces “in-plane” birefringence, which is enhanced by subsequent thermal annealing up to values as high as 0.34. The nonlinear response of Corona poled films with “in-plane” anisotropy is governed by three independent NLO dij coefficients, evidencing symmetry different from the usual (C∞v). For irradiated films, stable values d31 = 1.4, d32 = 0.9 and d33 = 11 pm·V−1 are measured at 1.9 µm. A noticeable higher d31/d32 ratio is obtained for preirradiated and annealed films. The proposed two-step method consisting of light irradiation and heating is an effective strategy to tailor the polar molecular orientation of nonlinear liquid crystalline azopolymers., Financial support from MEC-FEDER (MAT2008-06522-C02-01 and -02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. RA wishes to thank the Spanish Government for a grant (FPI program, no. BES2006-12104).

9 pages, 8 figures, 3 tables., The synthesis and characterization of a series of supramolecular polymeric complexes formed by H-bonding interactions between benzoic acid and azopyridine derivatives are described. A series of polymeric networks have been synthesized using a polymethacrylate bearing benzoic acid units as side groups, and several polymers with azopyridine as H-acceptor side groups. Furthermore, low-molecular-weight pyridine derivatives have been used to prepare an homologous side-chain polymer, and a network with azopyridine as a non-covalent crosslinker. Special attention was paid to the thermal and mesomorphic properties of these materials, which were studied by DSC, POM, and XRD., Financial support from the MEC-FEDER Spanish project (MAT-2005-06373-C02-01) is gratefully acknowledged. L. S. C. acknowledges the BSCH-UZ grant and the Brazilian government for a CAPES grant.

A poly[(R,S)-3-hydroxybutyrate] macroinitiator (PHB-MI) was obtained through the condensation reaction of poly[(R,S)-3-hydroxybutyrate] (PHB) oligomers containing dihydroxyl end functionalities with 4,4′-azobis(4-cyanopentanoyl chloride). The PHB-MI obtained in this way had hydroxyl groups at two end of the polymer chain and an internal azo group. The synthesis of ABA-type PHB-b-PMMA block copolymers [where A is poly(methyl methacrylate) (PMMA) and B is PHB] via PHB-MI was accomplished in two steps. First, multiblock active copolymers with azo groups (PMMA-PHB-MI) were prepared through the redox free-radical polymerization of methyl methacrylate (MMA) with a PHB-MI/Ce(IV) redox system in aqueous nitric acid at 40°C. Second, PMMA-PHB-MI was used in the thermal polymerization of MMA at 60°C to obtain PHB-b-PMMA. When styrene (S) was used instead of MMA in the second step, ABCBA-type PMMA-b-PHB-b-PS multiblock copolymers [where C is polystyrene (PS)] were obtained. In addition, the direct thermal polymerization of the monomers (MMA or S) via PHB-MI provided AB-type diblocks copolymers with MMA and BCB-type triblock copolymers with S. The macroinitiators and block copolymers were characterized with ultraviolet–visible spectroscopy, nuclear magnetic resonance spectroscopy, gel permeation chromatography, cryoscopic measurements, and thermogravimetric analysis. The increases in the intrinsic viscosity and fractional precipitation confirmed that a block copolymer had been obtained. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1789–1796, 2004

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. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the MICIIN-FEDER project CTQ2009-09030, MAT2011-27978-C02-02 and Diputación General de Aragón-Fondo Social Europeo (DGA-FSE) is gratefully acknowledged. R.C.-P. acknowledges a fellowship from the Ministerio de Educación y Ciencia.

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., Financial support from the Spanish projects MAT2011-27978-C02-01 and MAT2011-27978-C02-02, FEDER funding, and Gobierno de Aragón and Fondo Social Europeo is gratefully acknowledged. E. Blasco acknowledges the financial support from a JAE grant.

11 páginas, 6 figuras, 5 tablas, 1 esquema., Azobenzene monomeric precursors bearing piperazine as donor moiety with different withdrawing groups and derived side chain polymethacrylates have been prepared and characterized. Monomers having terminal cyano or nitro groups, and the corresponding polymers, exhibited smectic A phases. Linear and nonlinear optical properties of every monomer and thin films of the cyano polymer (pol-PZ-CN) have been also studied. UV-vis spectroscopy revealed out-of-plane orientation in the as prepared films, as confirmed by waveguide refractive index measurements. Moreover, absorption spectra indicated the presence of azo aggregates in these films. The initial molecular arrangement has been modified by applying thermal annealing within the mesophase range and UV-blue irradiation. Although thermal annealing resulted in a significant amplification of the out-of-plane optical anisotropy due to thermotropic self-organization of side chain azo moieties, irradiation with 440 nm light induced some disruption of aggregates. The nonlinear optical response of Corona poled films has been studied by second harmonic generation measurements, and the influence of the molecular arrangement on the nonlinear dij coefficients has been analyzed. The more efficient poling corresponded to preirradiated films. In any case, a noticeable degree of polar order (70% of the initial d33 value) remained for several months after the poling in films kept at RT., Financial support from MICINN-FEDER (MAT2008-06522- C02-01 and -02) and Gobierno de Aragón-Fondo Social Europeo (E39) is gratefully acknowledged. R. Alicante thanks the Spanish Government for a grant (FPI program, No. BES2006-12104).

We have incorporated push-pull azobenzene units into diblock-copolymer micelles by supramolecular assembly. Specifically, we encapsulated a phenol-functionalized chromophore, DO13, within PS-b-P4VP micelles in toluene by means of H-bond interactions developed between DO13molecules and pyridine groups of P4VP block. The solutions were spincoated onto glass substrates to result in multi- or mono-layered thin films of micelles with P4VP(DO13) core and PS corona. We showed that the use of DO13 as building block of micellar aggregates allow us to manipulate the developed nanostructures. Spherical to cylindrical micellar transition was found when we increased the degree of chromophore complexation. Besides, it was found that the polymer concentration in the solution plays an important role in determining the micellar nanostructures. The chain extension and change in composition of the P4VP core in the presence of the chromophore, may be responsible for the structural changes observed in the micelles. The optical properties of the thin films have been investigated focusing on the effect of the micellar morphology over the photo-induced birefringence. The optical anisotropy increased with respect to the analogous homogenous system P4VP(DO13) indicating that the protective micelle environment can enhance the optical properties of the embedded chromophores significantly. Besides, we showed very interesting new results in which we have related changes in optical properties with the film morphology (spheres to cylinders). This can be exploited for producing optical devices having improved optoelectronic properties and stability. Fil: Sáiz, Luciana María. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina Fil: Oyanguren, Patricia Angelica. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina Fil: Galante, Maria Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina Fil: Zucchi, Ileana Alicia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentina

Nanoindentation studies on thin films of the widely used azo polymer pDR1A and a supramolecular polymer–azobenzene complex p4VP(DY7)0.5 demonstrate significant light-induced softening upon visible-light irradiation due to trans–cis–trans photoisomerization of the azobenzene units. More specifically, the strain-rate sensitivities of pDR1A and p4VP(DY7)0.5 upon 532 nm irradiation increase by 80% and 120%, respectively. These results imply a photosoftening contribution to the mechanisms of light-induced surface patterning of azo polymers and the photomechanical effect. The finding that under the experimental conditions used photosoftening is more significant in the supramolecular complex than in the covalently functionalized polymer highlights the potential of noncovalent functionalization strategies in designing materials with efficient photomechanical response, and nanoindentation provides a powerful technique to quantify the connection between the photoinduced changes in mechanical properties and photoinduced macroscopic movement of azo polymer films.

International audience; 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.