| 1. |
- Lutfor, Rahman, et al.
(författare)
-
Synthesis and characterization of bent-shaped azobenzene monomers: Guest–host effects in liquid crystals with azo dyes for optical image storage devices
- 2009
-
Ingår i: Optical Materials. - : Elsevier BV. - 0925-3467. ; 32:1, s. 176-183
-
Tidskriftsartikel (refereegranskat)abstract
- Six novel bent-shaped monomers were synthesized such as substituted/or non-substituted 1,3-phenylene bis-{4-[(4-allyloxy)phenylazo]benzoate} (4a–c) and substituted/or non-substituted 1,3-phenylene bis-{4-[3-(4-allyloxy-3-fluoro)phenylazo]benzoate} (4d–f) in which azobenzene moiety in the periphery and substituted/or non-substituted resorcinol as central unit with polymeriable double bonds are linked at both ends of all the molecules. The mesophase behavior was investigated using polarizing optical microscopy, DSC and XRD measurements. Four members of the family show an intercalated smectic (Smintercal) phase and two were crystalline in nature. The trans-form of azo compounds (4a–f) showed a strong band in the UV region (355–366 nm), which was attributed to the p–p* transition, and a weak band in the visible region at 455–465 nm due to the n–p* transition. When one of the azo dye (4d) is mixed with liquid crystal as a guest, showed greater increase in thermal back relaxation time which is useful for creation of optical image storage devices.
|
|
| 2. |
- Lutfor, Rahman, et al.
(författare)
-
Synthesis and photoswitching properties of bent-shaped liquid crystals containing azobenzene monomers
- 2009
-
Ingår i: Liquid Crystals. - : Informa UK Limited. - 0267-8292 .- 1366-5855. ; 36:4
-
Tidskriftsartikel (refereegranskat)abstract
- Three novel bent-shaped monomers, namely 1,3-phenylene bis-{4-[4-(n-allyloxyalkyloxy)phenylazo]benzoate} 5a–c, containing azobenzene as side arms, resorcinol as central units and terminal double bonds as polymerisable functional groups were synthesised and characterised. The mesophase behaviour was investigated by polarising optical microscopy, differential scanning calorimetry and X-ray diffraction measurements and it was found that all three compounds display SmAintercal mesophases. These bent-shaped molecules exhibit strong photoisomerisation behaviour in solutions in which trans to cis isomerisation takes about 50 seconds whereas the reverse process takes almost 31 hours
|
|
| 3. |
- Scholtysek, Peggy, et al.
(författare)
-
A T-Shaped Amphiphilic Molecule Forms Closed Vesicles in Water and Bicelles in Mixtures with a Membrane Lipid
- 2012
-
Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 116:16, s. 4871-4878
-
Tidskriftsartikel (refereegranskat)abstract
- The T-shaped amphiphilic molecule A6/6 forms a columnar hexagonal liquid-crystalline phase between the crystalline and the isotropic liquid when studied in bulk (Chen et al., 2005). Because of the hydrophilic and flexible oligo(oxyethylene) side chain terminated by a 1-acylamino-1-deoxy-d-sorbitol moiety attached to a rigid terphenyl core with terminal hexyloxy alkyl chains, it was expected that also formation of lyotropic phases could be possible. We therefore studied the behavior of A6/6 in water and also in mixtures with bilayer-forming phospholipids, such as dipalmitoyl-phosphatidylcholine (DPPC), using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), cryo-transmission electron microscopy (cryo-TEM), dynamic light scattering (DLS), and solid-state nuclear magnetic resonance (ssNMR). DSC showed for the pure A6/6 suspended in water a phase transition at ca. 23 °C. TEM and cryo-TEM showed vesicular as well as layered structures for pure A6/6 in water below and above this phase transition. By atomic force microscopy (AFM), the thickness of the layer was found to be 5?6 nm. This leads to a model for a bilayer formed by A6/6 with the laterally attached polar side chains shielding the hydrophobic layer built up by the terphenyl core with the terminal alkyl chains of the molecules. For DPPC:A6/6 mixtures (10:1), the DSC curves indicated a stabilization of the lamellar gel phase of DPPC. Negative staining TEM and cryo-TEM images showed planar bilayers with hexagonal morphology and diameters between 50 and 200 nm. The hydrodynamic radius of these aggregates in water, investigated by dynamic light scattering (DLS) as a function of time and temperature, did not change indicating a very stable aggregate structure. The findings lead to the proposition of a new bicellar structure formed by A6/6 with DPPC. In this model, the bilayer edges are covered by the T-shaped amphiphilic molecules preventing very effectively the aggregation to larger structures.
|
|
