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A systematical calculation is performed to explore the equilibrium phase behaviors of linear-dendritic triblock copolymer A B ( 2 g + 1 − 2 ) C 2 g + 1 ( g is the generation number of the block B, and G g is short for A B ( 2 g + 1 − 2 ) C 2 g + 1 ) from G1 to G5 by using self-consistent field theory. Eight phases are found: two-colored lamellar phase, three-colored lamellar phase, hexagonal phase, core shell hexagonal phase, tetragonal phase, core shell tetragonal phase, two interpenetrating tetragonal phase, lamellar phase with beads except disordered phase, by varying the interaction parameters between different blocks, the volume fractions of the blocks and the generation number. While investigating the effect of linear coil length on morphology, we find the longer linear length ( f A = 0.5) for G1, G2 can be beneficial to form the lamellar phase, however, tend to form hexagonal phase easily with generation number increasing from 3 to 5, and short linear length ( f A = 0.2) can be better for inducing hexagonal phase from G1 to G5. It becomes more and more difficult to phase separate with generation number increasing from 1 to 5 due to the architectural complexity. However, increasing the interaction parameters is helpful to facilitate phase separation. It is likely to offer new opportunity for designing nanomaterials and applying to template technology by finely controlling the dendron generations, length of the linear chain, interaction parameters of linear-dendritic triblock copolymers. [ABSTRACT FROM AUTHOR]

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]

Abstract: A series of carboxylic acid functionalized hybrid linear-dendritic block copolymers (LDBCs) derived from methoxy poly(ethylene glycol) (MPEG) and variant generation dendrons from 2,2-bis(hydroxymethyl) propionic acid were synthesized and employed as CaCO3 crystallization growth modifiers. Mainly spherical vaterite particles of gradually reduced sizes were produced with the increase of the polymer additive concentration and/or the dendron segment generation number, while the incorporated polymer organic components in the particles increased for the promoted binding efficiency and ever enhanced adsorption ability. A higher mineralization temperature resulted in significantly larger particle size and partly calcite formation. Under the same molar concentration of carboxylic acid, the same size level particles were obtained which manifested the crucial role of the functional group, meanwhile, the slight decrease of the spherical vaterite diameters with increasing generation number and especially the formation of particular pine-cone shaped calcite crystals also revealed the significant effect of the architectural structure of variant generations and some special characters of the hybrid LDBC structures. [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]