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Liquid crystal nanoscience has aroused intensive interests mainly due to their unique and collective properties and a variety of potential applications. In this paper, gold nanoparticles (GNPs) coated with alkoxy azobenzene mesogenic thiol ligands of different length polymethylene spacer and linear alkyl thiol co-ligands have been prepared. The thermal properties, phase behavior of thus obtained hybrid GNPs and photophysical properties of their solid-state films have been investigated by differential scanning calorimetry (DSC), variable-temperature small and wide angle X-ray scattering (SAXS/WAXS) and UV–vis spectroscopy. The hybrid GNPs exclusively passivated with azobenzene mesogenic ligands showed lamellar structure while those with mixed ligands exhibited hexagonal columnar superstructure, and the latter complex hybrid GNPs exhibited noticeably improved thermolysis resistance. Moreover, it is very interesting that the solid-state films of the hybrid GNPs displayed reversible photoresponse owing to the trans – cis transformation of azobenzene mesogenic ligands, and compared with the hybrid GNPs coated with mesogenic ligands only, those with mixed ligands exhibited faster photoisomerization rate upon alternate UV and visible light irradiation, which may have some promising applications. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, based on the synthesis of precursor linear-dendritic block copolymers (LDBCs) with a linear poly(ethylene glycol) (PEG) block of molecular weight around 2000 and dendritic polyamidoamine (PAMAM) segments of generation G0 to G3, a series of azobenzene-containing amphiphilic LDBCs mPEG-dendr[PAMAM-(AZO) n ] (n = 2, 4, 8, 16) have been successfully prepared in moderate yields 45–60%, through complete Michael addition between the peripheral amine groups of dendritic segment and the reactive azobenzene acrylate mesogen units bearing octyloxy tails and flexible decylmethylene spacers. The purified copolymers have been characterized and confirmed by NMR, FT-IR, MALDI-TOF MS, and GPC showing narrow molecular weight distribution in the range 1.09–1.20. A generation-dependent polymeric micellar aggregation behavior of thus obtained amphiphilic LDBCs from nanofibers of uniform diameter around 20 nm to nanospheres/oval sheets, vesicles, and porous large compound micelles (LCMs) of micrometer size has been demonstrated in selective solvent mixture of dioxane/water. Furthermore, photoisomerization transformation of these azobenzene-containing LDBCs and their kinetics of reversible trans-cis-trans photochemical transitions in THF solution have also been investigated, the measured trans-cis photoisomerization rate constant 0.0240 s−1 for G3 copolymer is twice of the 0.0127 s−1 determined for the precursor azobenzene compound, manifesting a kind of promising photoresponsive copolymer materials. [Copyright &y& Elsevier]

Azobenzene-containing polymers (azopolymers) are a kind of intensively explored fascinating photoresponsive materials, liquid crystalline (LC) azopolymers with excellent film-forming, ordered structure and self-repairing capability are endowed with enhanced photoisomerization and photoalignment characteristics capable of developing into photo-modulated smart surfaces. Here in this work, two azobenzene side-chain LC polynorbornenes of PNB-Azo-n with different DP of n = 50 and 100 have been well synthesized through ring-opening metathesis polymerization (ROMP). The polynorbornene backbone of less flexibility with larger spacing between adjacent azobenzene side groups endows stronger inhibition for H-aggregation and better photoresponsiveness. The high-DP azopolynorbornene of PNB-Azo-100 thin films well behave as command surface for the upper layer nematic LC molecules thanks to their better performance in photoisomerization and photoalignment, together with their good compatibility and dissolution-resistance to the nematic LC mixture of E7. Selectively optically readable LC graphic writings at normal size through various photomasks have been demonstrated, and higher grid resolution up to sub-ten micrometer with a digital micromirror device (DMD) based dynamic photopatterning system has been achieved. Therefore, such kind of LC azopolynorbornenes demonstrate promising applications in LC photoalignment system and photoresponsive devices for potential anti-forgery document security and smart card technology. Image 1 • Synthesis of LC polynorbornenes with side-chain azobenzene via ROMP (DP 50, 100). • Semi-rigid polynorbornene inhibiting H-aggregation and promoting photoresponse. • Photoaligned high-DP azopolymer thin films as command surface for LC E7 patterning. • High grid resolution up to sub-ten-micrometer from DMD based dynamic photopatterning. • LC photoalignment and photoresponsive systems promising for anti-forgery application. [ABSTRACT FROM AUTHOR]